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Groovy reactor grails realtime web devoxx 2013

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Stéphane Maldini
Stéphane Maldini
Technologie
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Groovy, Reactor, Grails 
 & the realtime web Guillaume Laforge 
 @glaforge ! Stéphane Maldini
 @smaldini !
Stéphane Maldini Consultant and Reactor committer at . ! @smaldini
Guillaume Laforge Groovy project lead at . ! @glaforge http://glaforge.appspot.com
Les Cast Codeurs
0 t r a P Introduction
Valuable users don’t like to wait
Realtime web applications are about the « now »
Show users live updates as they come
Show users live updates as they come A « push » approach vs a « pull » approach
Show users live updates as they come A « push » approach vs a « pull » approach Handle a big volume of events
Show users live updates as they come A « push » approach vs a « pull » approach Handle a big volume of events React fast to new events
Show users live updates as they come A « push » approach vs a « pull » approach Handle a big volume of events React fast to new events Use promises, events, streams to react fast and stream updates to users as they are ready
Show users live updates as they come Avoid blocking and state A « push » approach vs a « pull » approach Handle a big volume of events React fast to new events Use promises, events, streams to react fast and stream updates to users as they are ready
Show users live updates as they come Fail gracefully Avoid blocking and state A « push » approach vs a « pull » approach Handle a big volume of events React fast to new events Use promises, events, streams to react fast and stream updates to users as they are ready
Sharp tools: Groovy, Reactor & Grails
1 t r a P Groovy
Groovy… an Open Source 
 alternative language 
 for the JVM
Groovy… Object-oriented, dynamic, with a functional flavor
Groovy… But also supports 
 static type checking & 
 static compilation
1.7 million 
 downloads
 per year
Yup, we’re all using Groovy!
Simplify the life of (Java) developers
Groovy as a Java superset
Groovy as a Java superset It’s so easy to learn!
As safe and fast as Java with static type checking & compilation
As safe and fast as Java with static type checking & compilation
new  MarkupBuilder().html  {          head  {                  title  "The  Script  Bowl"          }   !        body  {                  div(class:  "banner")  {                          p  "Groovy  rocks!"                  }          }   }
move  forward  at  3.km/h Expressive, Concise, Readable
Speaking of conciseness... A full Spring app in the span of a tweet! @RestController   class  App  {          @RequestMapping("/")          String  home()  {  "Hello  World!"  }   }
Great for scripting
Great for scripting Fit for Domain-Specific Languages
Great for scripting Fit for Domain-Specific Languages Most seamless integration & interoperability wih java!
Great for scripting Full-blown reactive applications too! Fit for Domain-Specific Languages Most seamless integration & interoperability wih java!
Most Java code is also valid Groovy code!
Most Java code is also valid Groovy code! Any Java developer is a Groovy developer!
Flat learning curve
Flat learning curve Easy to learn
Scripts versus Classes public  class  Main  {          public  static  void  main(String[]  args)  {                  System.out.println("Hello");          }   } vs @glaforge — @smaldini / #DV13-rtweb !26
Scripts versus Classes public  class  Main  {          public  static  void  main(String[]  args)  {                  System.out.println("Hello");          }   } vs println  "Hello" @glaforge — @smaldini / #DV13-rtweb !26
Optional
Semicolons Optional
Semicolons Optional Parentheses
Semicolons Optional return keyword Parentheses
Semicolons Parentheses Optional return keyword public keyword
Semicolons Optional return keyword Parentheses Typing! public keyword
Optional... public  class  Greeter  {          private  String  owner;   !        public  String  getOwner()  {                  return  owner;          }   !        public  void  setOwner(String  owner)  {                  this.owner  =  owner;          }   !        public  String  greet(String  name)  {                  return  "Hello  "  +  name  +  ",  I  am  "  +  owner;          }   }   ! Greeter  greeter  =  new  Greeter();   greeter.setOwner("Guillaume");   ! System.out.println(greeter.greet("Marion")); @glaforge — @smaldini / #DV13-rtweb !28
Optional... Semicolons public  class  Greeter  {          private  String  owner;   !        public  String  getOwner()  {                  return  owner;          }   !        public  void  setOwner(String  owner)  {                  this.owner  =  owner;          }   !        public  String  greet(String  name)  {                  return  "Hello  "  +  name  +  ",  I  am  "  +  owner;          }   }   ! Greeter  greeter  =  new  Greeter();   greeter.setOwner("Guillaume");   ! System.out.println(greeter.greet("Marion")); @glaforge — @smaldini / #DV13-rtweb !28
Optional... public  class  Greeter  {          private  String  owner   !        public  String  getOwner()  {                  return  owner          }   !        public  void  setOwner(String  owner)  {                  this.owner  =  owner          }   !        public  String  greet(String  name)  {                  return  "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Greeter  greeter  =  new  Greeter()   greeter.setOwner("Guillaume")   ! System.out.println(greeter.greet("Marion")) @glaforge — @smaldini / #DV13-rtweb !29
Optional... public  class  Greeter  {          private  String  owner   !        public  String  getOwner()  {                  return  owner          }   !        public  void  setOwner(String  owner)  {                  this.owner  =  owner          }   !        public  String  greet(String  name)  {                  return  "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Greeter  greeter  =  new  Greeter()   greeter.setOwner("Guillaume")   ! System.out.println(greeter.greet("Marion")) @glaforge — @smaldini / #DV13-rtweb !30
Optional... public  class  Greeter  {          private  String  owner   !        public  String  getOwner()  {                  return  owner          }   !        public  void  setOwner(String  owner)  {                  this.owner  =  owner          }   !        public  String  greet(String  name)  {                  return  "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Greeter  greeter  =  new  Greeter()   greeter.setOwner("Guillaume")   Parentheses ! System.out.println(greeter.greet("Marion")) @glaforge — @smaldini / #DV13-rtweb !30
Optional... public  class  Greeter  {          private  String  owner   !        public  String  getOwner()  {                  return  owner          }   !        public  void  setOwner(String  owner)  {                  this.owner  =  owner          }   !        public  String  greet(String  name)  {                  return  "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Greeter  greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   ! System.out.println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !31
Optional... public  class  Greeter  {          private  String  owner   !        public  String  getOwner()  {                  return  owner          }   !        public  void  setOwner(String  owner)  {                  this.owner  =  owner          }   ! return keyword        public  String  greet(String  name)  {                  return  "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Greeter  greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   ! System.out.println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !31
Optional... public  class  Greeter  {          private  String  owner   !        public  String  getOwner()  {                                owner          }   !        public  void  setOwner(String  owner)  {                  this.owner  =  owner          }   !        public  String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Greeter  greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   ! System.out.println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !32
Optional... public  class  Greeter  {          private  String  owner   !        public  String  getOwner()  {                                owner          }   ! public keyword        public  void  setOwner(String  owner)  {                  this.owner  =  owner          }   !        public  String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Greeter  greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   ! System.out.println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !32
Optional...              class  Greeter  {          private  String  owner   !                      String  getOwner()  {                                owner          }   !                      void  setOwner(String  owner)  {                  this.owner  =  owner          }   !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Greeter  greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   ! System.out.println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !33
Optional...              class  Greeter  {          private  String  owner   !                      String  getOwner()  {                                owner          }   !                      void  setOwner(String  owner)  {                  this.owner  =  owner          }   !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   optional typing ! Greeter  greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   ! System.out.println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !33
Optional...              class  Greeter  {          private  String  owner   !                      String  getOwner()  {                                owner          }   !                      void  setOwner(String  owner)  {                  this.owner  =  owner          }   !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! def          greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   ! System.out.println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !34
Optional...              class  Greeter  {          private  String  owner   !                      String  getOwner()  {                                owner          }   !                      void  setOwner(String  owner)  {                  this.owner  =  owner          }   !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   handy println shortcut def          greeter  =  new  Greeter()   ! greeter.setOwner  "Guillaume"   ! System.out.println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !34
Optional...              class  Greeter  {          private  String  owner   !                      String  getOwner()  {                                owner          }   !                      void  setOwner(String  owner)  {                  this.owner  =  owner          }   !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! def          greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !35
Optional... verbose Java properties!              class  Greeter  {          private  String  owner   !                      String  getOwner()  {                                owner          }   !                      void  setOwner(String  owner)  {                  this.owner  =  owner          }   !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! def          greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !35
Optional...              class  Greeter  {                          String  owner   ! ! ! ! ! ! ! ! !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! def          greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !36
Optional...              class  Greeter  {                          String  owner   ! ! ! ! ! ! ! ! !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Property notation def          greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !36
Optional...              class  Greeter  {                          String  owner   ! ! ! ! ! ! ! ! !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! def          greeter  =  new  Greeter()   greeter.owner  =    "Guillaume"   !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !37
Optional...              class  Greeter  {                          String  owner   ! ! ! ! ! ! ! ! Named argument                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner   constructor !        }   }   ! def          greeter  =  new  Greeter()   greeter.owner  =    "Guillaume"   !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !37
Optional...              class  Greeter  {                          String  owner   ! ! ! ! ! ! ! ! !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! def          greeter  =  new  Greeter(owner:  "Guillaume")   ! !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !38
Optional...              class  Greeter  {                          String  owner   ! ! ! ! ! ! Interpolated strings! (aka GStrings) ! ! !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! def          greeter  =  new  Greeter(owner:  "Guillaume")   ! !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !38
Optional...              class  Greeter  {                          String  owner   ! ! ! ! ! ! ! ! !                      String  greet(String  name)  {                                "Hello  ${name},  I  am  ${owner}"          }   }   ! def          greeter  =  new  Greeter(owner:  "Guillaume")   ! !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !39
Optional...              class  Greeter  {                          String  owner   ! ! ! ! Let’s reformat that mess of whitespace! ! ! ! ! !                      String  greet(String  name)  {                                "Hello  ${name},  I  am  ${owner}"          }   }   ! def          greeter  =  new  Greeter(owner:  "Guillaume")   ! !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !39
Optional... class  Greeter  {          String  owner   !        String  greet(String  name)  {                "Hello  ${name},  I  am  ${owner}"          }   }   ! def  greeter  =  new  Greeter(owner:  "Guillaume")   ! println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !40
Optional... public  class  Greeter  {          private  String  owner;   !        public  String  getOwner()  {   class  Greeter  {                  return  owner;          String  owner          }   ! !        String  greet(String  name)  {          public  void  setOwner(String  owner)  {                "Hello  ${name},  I  am  ${owner}"                  this.owner  =  owner;          }          }   }   ! !        public  String  greet(String  name)  {   def  greeter  =  new  Greeter(owner:  "Guillaume")                  return  "Hello  "  +  name  +  ",  I  am  "  +  owner;   !        }   println  greeter.greet("Marion") }   ! Greeter  greeter  =  new  Greeter();   greeter.setOwner("Guillaume");   ! System.out.println(greeter.greet("Marion")); @glaforge — @smaldini / #DV13-rtweb !40
Optional... class  Greeter  {          String  owner   !        String  greet(String  name)  {                "Hello  ${name},  I  am  ${owner}"          }   }   ! def  greeter  =  new  Greeter(owner:  "Guillaume")   ! println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !40
Native syntax constructs //  closures   def  adder  =  {  a,  b  -­‐>  a  +  b  }   ! //  lists   def  list  =  [1,  2,  3,  4,  5]   ! //  maps   def  map  =  [a:  1,  b:  2,  c:  3]   ! //  regular  expressions   def  regex  =  ~/.*foo.*/   ! //  ranges   def  range  128..255 @glaforge — @smaldini / #DV13-rtweb !41
Closures — the basics • Functions as first-class citizen of the language def  adder  =  {  a,  b  -­‐>  a  +  b  }   ! assert  adder(1,  2)  ==  3   assert  adder('a',  'b')  ==  'ab' @glaforge — @smaldini / #DV13-rtweb !42
Closures — the basics • Functions as first-class citizen of the language Closure parameters def  adder  =  {  a,  b  -­‐>  a  +  b  }   ! assert  adder(1,  2)  ==  3   assert  adder('a',  'b')  ==  'ab' @glaforge — @smaldini / #DV13-rtweb !42
Closures — the basics • Functions as first-class citizen of the language Assign a function Closure into a variable parameters def  adder  =  {  a,  b  -­‐>  a  +  b  }   ! assert  adder(1,  2)  ==  3   assert  adder('a',  'b')  ==  'ab' @glaforge — @smaldini / #DV13-rtweb !42
Closures — the basics • Functions as first-class citizen of the language Assign a function Closure into a variable parameters def  adder  =  {  a,  b  -­‐>  a  +  b  }   ! assert  adder(1,  2)  ==  3   assert  adder('a',  'b')  ==  'ab' Short form of: adder.call(‘a’, ‘b’) @glaforge — @smaldini / #DV13-rtweb !42
Closures — the basics • Functions as first-class citizen of the language Assign a function Closure into a variable parameters def  adder  =  {  a,  b  -­‐>  a  +  b  }   ! assert  adder(1,  2)  ==  3   assert  adder('a',  'b')  ==  'ab' Short form of: adder.call(‘a’, ‘b’) @glaforge — @smaldini / #DV13-rtweb Genericity with duck typing & operator overloading !42
Closures — explicit type ! def  intAdder  =  {  int  a,  int  b  -­‐>  a  +  b  } @glaforge — @smaldini / #DV13-rtweb !43
Closures — explicit type Be explicit about the types ! def  intAdder  =  {  int  a,  int  b  -­‐>  a  +  b  } @glaforge — @smaldini / #DV13-rtweb !43
Closures — implicit parameter def  doubler  =  {  it  *  2  }   ! assert  doubler(3)  ==  6   assert  doubler('a')  ==  'aa' @glaforge — @smaldini / #DV13-rtweb !44
Closures — implicit parameter Implicit parameter def  doubler  =  {  it  *  2  }   ! assert  doubler(3)  ==  6   assert  doubler('a')  ==  'aa' @glaforge — @smaldini / #DV13-rtweb !44
Closures — implicit parameter Implicit parameter def  doubler  =  {  it  *  2  }   ! assert  doubler(3)  ==  6   assert  doubler('a')  ==  'aa' Multiply also defined on strings @glaforge — @smaldini / #DV13-rtweb !44
Closures — variable arguments def  sum  =  {  ...  elements  -­‐>  
                                elements.sum()  }   ! assert  sum(1,  2)  ==  3   assert  sum('a',  'b',  'c')  ==  'abc' @glaforge — @smaldini / #DV13-rtweb !45
Closures — variable arguments Variable number of arguments def  sum  =  {  ...  elements  -­‐>  
                                elements.sum()  }   ! assert  sum(1,  2)  ==  3   assert  sum('a',  'b',  'c')  ==  'abc' @glaforge — @smaldini / #DV13-rtweb !45
Closures — variable arguments You can specify the type: int... Variable number of arguments def  sum  =  {  ...  elements  -­‐>  
                                elements.sum()  }   ! assert  sum(1,  2)  ==  3   assert  sum('a',  'b',  'c')  ==  'abc' @glaforge — @smaldini / #DV13-rtweb !45
Closures — default values def  mult  =  {  int  a,  int  b  =  10  -­‐>  a  *  b  }   ! assert  mult(2,  3)  ==  6   assert  mult(5)  ==  50 @glaforge — @smaldini / #DV13-rtweb !46
Closures — default values Default value def  mult  =  {  int  a,  int  b  =  10  -­‐>  a  *  b  }   ! assert  mult(2,  3)  ==  6   assert  mult(5)  ==  50 @glaforge — @smaldini / #DV13-rtweb !46
Closures — default values Default value def  mult  =  {  int  a,  int  b  =  10  -­‐>  a  *  b  }   ! assert  mult(2,  3)  ==  6   assert  mult(5)  ==  50 @glaforge — @smaldini / #DV13-rtweb Provided value for b !46
Closures — default values Default value def  mult  =  {  int  a,  int  b  =  10  -­‐>  a  *  b  }   ! assert  mult(2,  3)  ==  6   assert  mult(5)  ==  50 Default value used for b @glaforge — @smaldini / #DV13-rtweb Provided value for b !46
Closures — methods as functions def  logBase10  =  Math.&log10   def  printer  =  System.out.&println   ! assert  logBase10(10)  ==  1   printer  'abc' @glaforge — @smaldini / #DV13-rtweb !47
Closures — methods as functions Turn a method into a closure function def  logBase10  =  Math.&log10   def  printer  =  System.out.&println   ! assert  logBase10(10)  ==  1   printer  'abc' @glaforge — @smaldini / #DV13-rtweb !47
Closures — map / filter / reduce @glaforge — @smaldini / #DV13-rtweb !48
Closures — map / filter / reduce @groovy.transform.Immutable
 class  Person  {
        String  name
        int  age
 } @glaforge — @smaldini / #DV13-rtweb !48
Closures — map / filter / reduce @groovy.transform.Immutable
 class  Person  {
        String  name
        int  age
 } @glaforge — @smaldini / #DV13-rtweb !48
Closures — map / filter / reduce @groovy.transform.Immutable
 class  Person  {
        String  name
        int  age
 } def  persons  =  [
        new  Person('Guillaume',  36),
        new  Person('Marion',  5),
        new  Person('Erine',  1)
 ] @glaforge — @smaldini / #DV13-rtweb !48
Closures — map / filter / reduce @groovy.transform.Immutable
 class  Person  {
        String  name
        int  age
 } def  persons  =  [
        new  Person('Guillaume',  36),
        new  Person('Marion',  5),
        new  Person('Erine',  1)
 ] @glaforge — @smaldini / #DV13-rtweb !48
Closures — map / filter / reduce @groovy.transform.Immutable
 class  Person  {
        String  name
        int  age
 } def  persons  =  [
        new  Person('Guillaume',  36),
        new  Person('Marion',  5),
        new  Person('Erine',  1)
 ] def  names  =
        persons.findAll  {  it.age  <  18  }
                      .collect  {  it.name.toUpperCase()  }
                      .sort()
                      .join(',  ') @glaforge — @smaldini / #DV13-rtweb !48
Closures — map / filter / reduce @groovy.transform.Immutable
 class  Person  {
        String  name
        int  age
 } def  persons  =  [
        new  Person('Guillaume',  36),
        new  Person('Marion',  5),
        new  Person('Erine',  1)
 ] def  names  =
        persons.findAll  {  it.age  <  18  }
                      .collect  {  it.name.toUpperCase()  }
                      .sort()
                      .join(',  ') @glaforge — @smaldini / #DV13-rtweb !48
Closures — map / filter / reduce @groovy.transform.Immutable
 class  Person  {
        String  name
        int  age
 } def  persons  =  [
        new  Person('Guillaume',  36),
        new  Person('Marion',  5),
        new  Person('Erine',  1)
 ] def  names  =
        persons.findAll  {  it.age  <  18  }
                      .collect  {  it.name.toUpperCase()  }
                      .sort()
                      .join(',  ') assert  names  ==  "ERINE,  MARION" @glaforge — @smaldini / #DV13-rtweb !48
Closures — map / filter / reduce @groovy.transform.Immutable
 class  Person  {
        String  name
        int  age
 } def  persons  =  [
        new  Person('Guillaume',  36),
        new  Person('Marion',  5),
        new  Person('Erine',  1)
 ] find/findAll, inject, collect, flatten, min/max, unique, reverse, collate, groupBy, any/every, head/tail/last, count/countBy, combinations/ permutations/subsequences/ transpose, withDefault/ withLazyDefault def  names  =
        persons.findAll  {  it.age  <  18  }
                      .collect  {  it.name.toUpperCase()  }
                      .sort()
                      .join(',  ') assert  names  ==  "ERINE,  MARION" @glaforge — @smaldini / #DV13-rtweb !48
Closures — resource handling new  File('bible.txt').withReader  {  r  -­‐>          new  File('out.txt').withWriter  {  w  -­‐>                  r.eachLine  {  line  -­‐>                          if  (line.contains('Groovy'))                                  w  <<  line.toUpperCase()                  }          }   } @glaforge — @smaldini / #DV13-rtweb !49
Closures — resource handling Take care of properly opening / closing resources new  File('bible.txt').withReader  {  r  -­‐>          new  File('out.txt').withWriter  {  w  -­‐>                  r.eachLine  {  line  -­‐>                          if  (line.contains('Groovy'))                                  w  <<  line.toUpperCase()                  }          }   } @glaforge — @smaldini / #DV13-rtweb !49
Closures — custom control structures void  unless(boolean  cond,  Closure  c)  {          if  (!cond)  c()   }   ! unless  (10  <  9)  {          println  "less"   } @glaforge — @smaldini / #DV13-rtweb !50
Closures — custom control structures Closure as last argument void  unless(boolean  cond,  Closure  c)  {          if  (!cond)  c()   }   ! unless  (10  <  9)  {          println  "less"   } @glaforge — @smaldini / #DV13-rtweb !50
Closures — custom control structures Closure as last argument void  unless(boolean  cond,  Closure  c)  {          if  (!cond)  c()   }   ! unless  (10  <  9)  {          println  "less"   } @glaforge — @smaldini / #DV13-rtweb Equivalent to: unless(10<9, {...}) !50
Closures — custom control structures class  Reactor  {            void  on(Selector  s,  Closure  c)  {  …  }   }   …   reactor.on(  $(‘abc')  )  {  Event<String>  ev  -­‐>          …   } @glaforge — @smaldini / #DV13-rtweb !51
Closures — builders leverage closures import  groovy.json.*   ! def  json  =  new  JsonBuilder()   json.person  {          name  'Guillaume'          age  36          daughters  'Marion',  'Erine'          address  {                  street  '1  Main  Street'                  zip  75001                  city  'Paris'          }   } @glaforge — @smaldini / #DV13-rtweb !52
Closures — builders leverage closures import  groovy.json.*   ! def  json  =  new  JsonBuilder()   json.person  {          name  'Guillaume'          age  36          daughters  'Marion',  'Erine'          address  {                  street  '1  Main  Street'                  zip  75001                  city  'Paris'          }   } @glaforge — @smaldini / #DV13-rtweb Hierarchical data representation !52
Closures — builders leverage closures import  groovy.json.*   ! Hierarchical data representation def  json  =  new  JsonBuilder()   json.person  {          name  'Guillaume'          age  36   Closure blocks        daughters  'Marion',  'Erine'   delimiting the        address  {   structure                street  '1  Main  Street'                  zip  75001                  city  'Paris'          }   } @glaforge — @smaldini / #DV13-rtweb !52
Closures — builders leverage closures import  groovy.json.*   {          "person":  {   Hierarchical data def  json  =  new  JsonBuilder()                  "name":  "Guillaume",   representation                "age":  36,   json.person  {                  "daughters":  [          name  'Guillaume'                          "Marion",                          "Erine"          age  36                  ],   Closure blocks        daughters  'Marion',  'Erine'                  "address":  {   delimiting the                        "street":  "1  Main  Street",          address  {                          "zip":  75001,   structure                street  '1  Main  Street'                          "city":  "Paris"                  }                  zip  75001          }                  city  'Paris'   } !        }   } @glaforge — @smaldini / #DV13-rtweb !52
Closure — your own builders GroovyEnvironment.create  {          environment  {                  defaultDispatcher  =  "test"   !                dispatcher('test')  {                          type  =  DispatcherType.SYNCHRONOUS                  }          }   } @glaforge — @smaldini / #DV13-rtweb !53
Closure — your own builders GroovyEnvironment.create  {          environment  {                  defaultDispatcher  =  "test"   !                dispatcher('test')  {                          type  =  DispatcherType.SYNCHRONOUS                  }          }   } @glaforge — @smaldini / #DV13-rtweb !53
Closure — your own builders GroovyEnvironment.create  {          environment  {                  defaultDispatcher  =  "test"   !                dispatcher('test')  {                          type  =  DispatcherType.SYNCHRONOUS                  }          }   } @glaforge — @smaldini / #DV13-rtweb !53
Closure — your own builders GroovyEnvironment.create  {          environment  {                  defaultDispatcher  =  "test"   !                dispatcher('test')  {                          type  =  DispatcherType.SYNCHRONOUS                  }          }   } @glaforge — @smaldini / #DV13-rtweb !53
Closure — your own builders GroovyEnvironment.create  {          environment  {                  defaultDispatcher  =  "test"   !                dispatcher('test')  {                          type  =  DispatcherType.SYNCHRONOUS                  }          }   } @glaforge — @smaldini / #DV13-rtweb !53
Closure — your own builders Implement a builder extending BuilderSupport or FactoryBuilderSupport… GroovyEnvironment.create  {   or roll your own!        environment  {                  defaultDispatcher  =  "test"   !                dispatcher('test')  {                          type  =  DispatcherType.SYNCHRONOUS                  }          }   } @glaforge — @smaldini / #DV13-rtweb !53
Closure — your own builders Implement a builder extending BuilderSupport or FactoryBuilderSupport… GroovyEnvironment.create  {   or roll your own!        environment  {                  defaultDispatcher  =  "test"   abstract  class  BuilderSupport  {          abstract  void  setParent(Object  parent,  Object  child)   !        abstract  Object  createNode(Object  name)                  dispatcher('test')  {          abstract  Object  createNode(Object  name,  Object  value)          abstract  Object  createNode(Object  name,  Map  attributes)                          type  =  DispatcherType.SYNCHRONOUS          abstract  Object  createNode(Object  name,  Map  attributes,  Object  value)   }                  }          }   } @glaforge — @smaldini / #DV13-rtweb !53
GPath expressions • GPath expressions are like XPath 
 but for an object graph import  groovy.json.*   ! def  url  =  "https://api.github.com/repos/groovy/groovy-­‐core/commits"   ! def  commits  =  new  JsonSlurper().parseText(url.toURL().text)   ! assert  commits[0].commit.author.name  ==  'Cedric  Champeau' @glaforge — @smaldini / #DV13-rtweb !54
GPath expressions • GPath expressions are like XPath 
 but for an object graph import  groovy.json.*   ! def  url  =  "https://api.github.com/repos/groovy/groovy-­‐core/commits"   ! def  commits  =  new  JsonSlurper().parseText(url.toURL().text)   ! assert  commits[0].commit.author.name  ==  'Cedric  Champeau' GPath expression @glaforge — @smaldini / #DV13-rtweb !54
GPath expressions • GPath expressions are like XPath 
 but for an object graph import  groovy.json.*   ! def  url  =  "https://api.github.com/repos/groovy/groovy-­‐core/commits"   ! def  commits  =  new  JsonSlurper().parseText(url.toURL().text)   ! assert  commits[0].commit.author.name  ==  'Cedric  Champeau' GPath expression @glaforge — @smaldini / #DV13-rtweb Add find / findAll into the mix !54
GPath expressions • GPath expressions are like XPath 
 but for an object graph No (un)marshalling! import  groovy.json.*   ! def  url  =  "https://api.github.com/repos/groovy/groovy-­‐core/commits"   ! def  commits  =  new  JsonSlurper().parseText(url.toURL().text)   ! assert  commits[0].commit.author.name  ==  'Cedric  Champeau' GPath expression @glaforge — @smaldini / #DV13-rtweb Add find / findAll into the mix !54
Lists def  list  =  ['a',  'b',  'c']   ! list  <<  'd'   assert  list.contains('d')   ! assert  list.findAll  {  it.startsWith  'a'  }.size()  ==  1   assert  list.collect  {  it.toUpperCase()  }  
                                                              ==  ['A',  'B',  'C',  'D']   assert  list.inject('')  {  a,  b  -­‐>  a  +  b  }  ==  'abcd' @glaforge — @smaldini / #DV13-rtweb !55
Lists List definition def  list  =  ['a',  'b',  'c']   ! list  <<  'd'   assert  list.contains('d')   ! assert  list.findAll  {  it.startsWith  'a'  }.size()  ==  1   assert  list.collect  {  it.toUpperCase()  }  
                                                              ==  ['A',  'B',  'C',  'D']   assert  list.inject('')  {  a,  b  -­‐>  a  +  b  }  ==  'abcd' @glaforge — @smaldini / #DV13-rtweb !55
Lists List definition def  list  =  ['a',  'b',  'c']   ! list  <<  'd'   assert  list.contains('d')   Append an element (operator overloading) ! assert  list.findAll  {  it.startsWith  'a'  }.size()  ==  1   assert  list.collect  {  it.toUpperCase()  }  
                                                              ==  ['A',  'B',  'C',  'D']   assert  list.inject('')  {  a,  b  -­‐>  a  +  b  }  ==  'abcd' @glaforge — @smaldini / #DV13-rtweb !55
Lists List definition def  list  =  ['a',  'b',  'c']   ! list  <<  'd'   assert  list.contains('d')   Append an element (operator overloading) ! assert  list.findAll  {  it.startsWith  'a'  }.size()  ==  1   assert  list.collect  {  it.toUpperCase()  }  
                                                              ==  ['A',  'B',  'C',  'D']   assert  list.inject('')  {  a,  b  -­‐>  a  +  b  }  ==  'abcd' Functional-style map / filter / reduce with closures @glaforge — @smaldini / #DV13-rtweb !55
Maps def  map  =  [name:  'Guillaume',  age:  36]   ! map.daughters  =  ['Marion',  'Erine']   ! assert  map['daughters'].contains('Marion') @glaforge — @smaldini / #DV13-rtweb !56
Maps Map definition def  map  =  [name:  'Guillaume',  age:  36]   ! map.daughters  =  ['Marion',  'Erine']   ! assert  map['daughters'].contains('Marion') @glaforge — @smaldini / #DV13-rtweb !56
Maps Map definition def  map  =  [name:  'Guillaume',  age:  36]   ! map.daughters  =  ['Marion',  'Erine']   ! assert  map['daughters'].contains('Marion') Indexed access @glaforge — @smaldini / #DV13-rtweb !56
Maps Map definition def  map  =  [name:  'Guillaume',  age:  36]   ! map.daughters  =  ['Marion',  'Erine']   ! assert  map['daughters'].contains('Marion') Property notation access @glaforge — @smaldini / #DV13-rtweb Indexed access !56
Regular expressions def  pattern  =  ~/.*foo.*/   ! assert  "Alibaba"  ==~  /.*(ba){2}/   ! def  matcher  =  "Superman"  =~  /([A-­‐Z][a-­‐z]+)man/   assert  matcher[0][0]  ==  'Superman'   assert  matcher[0][1]  ==  'Super'   ! '75001  Paris'.find(/(d{5})s(w+)/)  {  match,  zip,  town  -­‐>          println  "The  Zip  code  of  ${town}  is  ${zip}"   } @glaforge — @smaldini / #DV13-rtweb !57
Regular expressions Pattern def  pattern  =  ~/.*foo.*/   ! assert  "Alibaba"  ==~  /.*(ba){2}/   ! def  matcher  =  "Superman"  =~  /([A-­‐Z][a-­‐z]+)man/   assert  matcher[0][0]  ==  'Superman'   assert  matcher[0][1]  ==  'Super'   ! '75001  Paris'.find(/(d{5})s(w+)/)  {  match,  zip,  town  -­‐>          println  "The  Zip  code  of  ${town}  is  ${zip}"   } @glaforge — @smaldini / #DV13-rtweb !57
Regular expressions Pattern def  pattern  =  ~/.*foo.*/   Match ! assert  "Alibaba"  ==~  /.*(ba){2}/   ! def  matcher  =  "Superman"  =~  /([A-­‐Z][a-­‐z]+)man/   assert  matcher[0][0]  ==  'Superman'   assert  matcher[0][1]  ==  'Super'   ! '75001  Paris'.find(/(d{5})s(w+)/)  {  match,  zip,  town  -­‐>          println  "The  Zip  code  of  ${town}  is  ${zip}"   } @glaforge — @smaldini / #DV13-rtweb !57
Regular expressions Pattern def  pattern  =  ~/.*foo.*/   Match ! assert  "Alibaba"  ==~  /.*(ba){2}/   Find ! def  matcher  =  "Superman"  =~  /([A-­‐Z][a-­‐z]+)man/   assert  matcher[0][0]  ==  'Superman'   assert  matcher[0][1]  ==  'Super'   ! '75001  Paris'.find(/(d{5})s(w+)/)  {  match,  zip,  town  -­‐>          println  "The  Zip  code  of  ${town}  is  ${zip}"   } @glaforge — @smaldini / #DV13-rtweb !57
Regular expressions Pattern def  pattern  =  ~/.*foo.*/   Match ! assert  "Alibaba"  ==~  /.*(ba){2}/   Find ! def  matcher  =  "Superman"  =~  /([A-­‐Z][a-­‐z]+)man/   assert  matcher[0][0]  ==  'Superman'   assert  matcher[0][1]  ==  'Super'   ! '75001  Paris'.find(/(d{5})s(w+)/)  {  match,  zip,  town  -­‐>          println  "The  Zip  code  of  ${town}  is  ${zip}"   } Nice way to decompose the matched regions @glaforge — @smaldini / #DV13-rtweb !57
Ranges def  range  =  'a'..'z'   ! assert  range.contains('m')   assert  range.contains('z')   ! def  exclusive  =  1..<10   ! assert  !exclusive.contains(10)   ! def  reverse  =  10..0   ! assert  reverse[0]  ==  10   assert  reverse[-­‐1]  ==  0 @glaforge — @smaldini / #DV13-rtweb !58
Ranges Range def  range  =  'a'..'z'   ! assert  range.contains('m')   assert  range.contains('z')   ! def  exclusive  =  1..<10   ! assert  !exclusive.contains(10)   ! def  reverse  =  10..0   ! assert  reverse[0]  ==  10   assert  reverse[-­‐1]  ==  0 @glaforge — @smaldini / #DV13-rtweb !58
Ranges Range def  range  =  'a'..'z'   ! assert  range.contains('m')   assert  range.contains('z')   ! def  exclusive  =  1..<10   Excluded upper bound ! assert  !exclusive.contains(10)   ! def  reverse  =  10..0   ! assert  reverse[0]  ==  10   assert  reverse[-­‐1]  ==  0 @glaforge — @smaldini / #DV13-rtweb !58
Ranges Range def  range  =  'a'..'z'   ! assert  range.contains('m')   assert  range.contains('z')   ! def  exclusive  =  1..<10   Excluded upper bound ! assert  !exclusive.contains(10)   ! def  reverse  =  10..0   Reverse range ! assert  reverse[0]  ==  10   assert  reverse[-­‐1]  ==  0 @glaforge — @smaldini / #DV13-rtweb !58
Ranges Range def  range  =  'a'..'z'   ! assert  range.contains('m')   assert  range.contains('z')   ! def  exclusive  =  1..<10   Excluded upper bound ! assert  !exclusive.contains(10)   ! def  reverse  =  10..0   Reverse range ! assert  reverse[0]  ==  10   assert  reverse[-­‐1]  ==  0 @glaforge — @smaldini / #DV13-rtweb Negative index count from the end !58
Strings, GStrings, multiline strings def  name  =  'Groovy'   def  tmpl  =  """          Dear  Mr  ${name},          You're  the  winner  of  the  lottery!          Yours  sincerly,          Dave   """   ! assert  tmpl.toString().contains('Groovy') @glaforge — @smaldini / #DV13-rtweb !59
Strings, GStrings, multiline strings Plain java.lang.String def  name  =  'Groovy'   def  tmpl  =  """          Dear  Mr  ${name},          You're  the  winner  of  the  lottery!          Yours  sincerly,          Dave   """   ! assert  tmpl.toString().contains('Groovy') @glaforge — @smaldini / #DV13-rtweb !59
Strings, GStrings, multiline strings Plain java.lang.String def  name  =  'Groovy'   Multiline string with def  tmpl  =  """   expression interpolation        Dear  Mr  ${name},          You're  the  winner  of  the  lottery!          Yours  sincerly,          Dave   """   ! assert  tmpl.toString().contains('Groovy') @glaforge — @smaldini / #DV13-rtweb !59
Surprising numbers... System.out.println(  2.0  -­‐  1.1  ); @glaforge — @smaldini / #DV13-rtweb !60
Surprising numbers... System.out.println(  2.0  -­‐  1.1  ); 0.8999999999999999 @glaforge — @smaldini / #DV13-rtweb !60
Surprising numbers... System.out.println(  2.0  -­‐  1.1  ); 0.8999999999999999 @glaforge — @smaldini / #DV13-rtweb !60
Surprising numbers... System.out.println(  3  /  2  ); @glaforge — @smaldini / #DV13-rtweb !61
Surprising numbers... System.out.println(  3  /  2  ); 1 @glaforge — @smaldini / #DV13-rtweb !61
Surprising numbers... System.out.println(  3  /  2  ); 1 @glaforge — @smaldini / #DV13-rtweb !61
BigDecimal by default! assert  2.0  -­‐  1.1  ==  0.9 assert  3  /  2  ==  1.5 @glaforge — @smaldini / #DV13-rtweb !62
BigDecimal by default! assert  2.0  -­‐  1.1  ==  0.9 assert  3  /  2  ==  1.5 One of the reasons why microbenchmarks sometimes showed Groovy to be slow... @glaforge — @smaldini / #DV13-rtweb !62
BigDecimal by default! assert  2.0  -­‐  1.1  ==  0.9 assert  3  /  2  ==  1.5 One of the reasons why microbenchmarks sometimes showed Groovy to be slow... @glaforge — @smaldini / #DV13-rtweb But you can use doubles & floats for performance, with ‘d’ or ‘f ’ suffixes or with explicit type !62
Powerful switch / case on steroids
Powerful switch / case on steroids switch(obj)  {          case  123:                  "number  123";              break          case  "abc":              "string  abc";              break          case  String:            "is  a  string";            break          case  [1,  2,  3]:      "in  list";                    break          case  ~/.*o+.*/:      "regex  match";            break          case  {  it  <  3  }:    "closure  criteria";  break          default:                    "unknown"   }
Named arguments move  obj,  x:  3,  y:  4 @glaforge — @smaldini / #DV13-rtweb !64
Named arguments move  obj,  x:  3,  y:  4 Normal argument @glaforge — @smaldini / #DV13-rtweb !64
Named arguments move  obj,  x:  3,  y:  4 Normal argument @glaforge — @smaldini / #DV13-rtweb Named argument !64
Named arguments move  obj,  x:  3,  y:  4 Normal argument Named argument Calls: move(Map m, Object) @glaforge — @smaldini / #DV13-rtweb !64
Command chains • Ability to chain method calls without parentheses and dots move  forward  at  3.km/h @glaforge — @smaldini / #DV13-rtweb !65
Command chains • Ability to chain method calls without parentheses and dots move  forward  at  3.km/h Actually equivalent to: move(forward).at(3.getKm().div(h)) @glaforge — @smaldini / #DV13-rtweb !65
Named arguments & command chains check  that:  vodka  tastes  good @glaforge — @smaldini / #DV13-rtweb !66
Named arguments & command chains check  that:  vodka  tastes  good Will call: check(that: vodka).tastes(good) @glaforge — @smaldini / #DV13-rtweb !66
Multiple assignment and destructuring def  (a,  b)  =  ['A',  'B']   ! (a,  b)  =  [b,  a]   ! def  (int  i,  int  j)  =  [1,  2]   ! def  geocode(String  place)  {          return  [45.4,  2.3]   }   ! def  (la,  lo)  =  geocode("Paris")   ! assert  la  ==  45.4  &&  lo  ==  2.3 @glaforge — @smaldini / #DV13-rtweb !67
Multiple assignment and destructuring def  (a,  b)  =  ['A',  'B']   ! (a,  b)  =  [b,  a]   Classic « swap » ! def  (int  i,  int  j)  =  [1,  2]   ! def  geocode(String  place)  {          return  [45.4,  2.3]   }   ! def  (la,  lo)  =  geocode("Paris")   ! assert  la  ==  45.4  &&  lo  ==  2.3 @glaforge — @smaldini / #DV13-rtweb !67
Multiple assignment and destructuring def  (a,  b)  =  ['A',  'B']   ! With types (a,  b)  =  [b,  a]   Classic « swap » ! def  (int  i,  int  j)  =  [1,  2]   ! def  geocode(String  place)  {          return  [45.4,  2.3]   }   ! def  (la,  lo)  =  geocode("Paris")   ! assert  la  ==  45.4  &&  lo  ==  2.3 @glaforge — @smaldini / #DV13-rtweb !67
Multiple assignment and destructuring def  (a,  b)  =  ['A',  'B']   ! With types (a,  b)  =  [b,  a]   Classic « swap » ! def  (int  i,  int  j)  =  [1,  2]   ! Method returning a list def  geocode(String  place)  {          return  [45.4,  2.3]   }   ! def  (la,  lo)  =  geocode("Paris")   ! assert  la  ==  45.4  &&  lo  ==  2.3 @glaforge — @smaldini / #DV13-rtweb !67
Multiple assignment and destructuring def  (a,  b)  =  ['A',  'B']   ! With types (a,  b)  =  [b,  a]   Classic « swap » ! def  (int  i,  int  j)  =  [1,  2]   ! Method returning a list def  geocode(String  place)  {          return  [45.4,  2.3]   }   Destructuring ! def  (la,  lo)  =  geocode("Paris")   ! assert  la  ==  45.4  &&  lo  ==  2.3 @glaforge — @smaldini / #DV13-rtweb !67
Multiple assignment and destructuring class  Point  {          double  x,  y   !        double  getAt(int  idx)  {                  if  (idx  ==  0)  x                  else  if  (idx  ==  1)  y                  else  throw  new  Exception("Wrong  index")          }   }   ! def  (x,  y)  =  new  Point(x:  48.3,  y:  3.5)   ! assert  x  ==  48.3  &&  y  ==  3.5 @glaforge — @smaldini / #DV13-rtweb !68
Multiple assignment and destructuring class  Point  {          double  x,  y   Method signature convention: getAt(int) !        double  getAt(int  idx)  {                  if  (idx  ==  0)  x                  else  if  (idx  ==  1)  y                  else  throw  new  Exception("Wrong  index")          }   }   ! def  (x,  y)  =  new  Point(x:  48.3,  y:  3.5)   ! assert  x  ==  48.3  &&  y  ==  3.5 @glaforge — @smaldini / #DV13-rtweb !68
Multiple assignment and destructuring class  Point  {          double  x,  y   Method signature convention: getAt(int) !        double  getAt(int  idx)  {                  if  (idx  ==  0)  x                  else  if  (idx  ==  1)  y                  else  throw  new  Exception("Wrong  index")          }   }   Transparent destructuring ! def  (x,  y)  =  new  Point(x:  48.3,  y:  3.5)   ! assert  x  ==  48.3  &&  y  ==  3.5 @glaforge — @smaldini / #DV13-rtweb !68
Operator overloading import  static  Unit.*   ! enum  Unit  {      M(1),  KM(1000)   !    double  mult      Unit(double  mult)  {          this.mult  =  mult      }   } @glaforge — @smaldini / #DV13-rtweb !69
Operator overloading import  static  Unit.*   ! enum  Unit  {      M(1),  KM(1000)   ! import  groovy.transform.Immutable   import  static  Unit.*      double  mult      Unit(double  mult)  {   !        this.mult  =  mult   @Immutable      }   class  Distance  {   }    double  q      Unit  u   !    Distance  plus(Distance  d)  {          new  Distance(    q  *      u.mult  +  
                                  d.q  *  d.u.mult,  M)      }   } @glaforge — @smaldini / #DV13-rtweb !69
Operator overloading import  static  Unit.*   ! import  static  Unit.*   enum  Unit  {      M(1),  KM(1000)   ! def  d10  =  new  Distance(10,  M)   ! import  groovy.transform.Immutable   def  d15  =  new  Distance(15,  M)      double  mult   import  static  Unit.*   !    Unit(double  mult)  {   ! def  d25  =  d10  +  d15          this.mult  =  mult   @Immutable   !    }   class  Distance  {   assert  d25.q  ==  25  &&  d25.u  ==  M }    double  q      Unit  u   !    Distance  plus(Distance  d)  {          new  Distance(    q  *      u.mult  +  
                                  d.q  *  d.u.mult,  M)      }   } @glaforge — @smaldini / #DV13-rtweb !69
Operator overloading import  static  Unit.*   ! import  static  Unit.*   enum  Unit  {      M(1),  KM(1000)   ! def  d10  =  new  Distance(10,  M)   ! import  groovy.transform.Immutable   def  d15  =  new  Distance(15,  M)      double  mult   import  static  Unit.*   !    Unit(double  mult)  {   ! def  d25  =  d10  +  d15          this.mult  =  mult   @Immutable   !    }   class  Distance  {   assert  d25.q  ==  25  &&  d25.u  ==  M }    double  q      Unit  u   Overload the ‘+’ operator @glaforge — @smaldini / #DV13-rtweb !    Distance  plus(Distance  d)  {          new  Distance(    q  *      u.mult  +  
                                  d.q  *  d.u.mult,  M)      }   } !69
Operator overloading import  static  Unit.*   ! import  static  Unit.*   enum  Unit  {      M(1),  KM(1000)   ! def  d10  =  new  Distance(10,  M)   ! import  groovy.transform.Immutable   def  d15  =  new  Distance(15,  M)      double  mult   import  static  Unit.*   !    Unit(double  mult)  {   ! def  d25  =  d10  +  d15          this.mult  =  mult   @Immutable   !    }   class  Distance  {   assert  d25.q  ==  25  &&  d25.u  ==  M }    double  q      Unit  u   Overload the ‘+’ operator @glaforge — @smaldini / #DV13-rtweb !    Distance  plus(Distance  d)  {          new  Distance(    q  *      u.mult  +  
                                  d.q  *  d.u.mult,  M)      }   } Use ‘+’ !69
Operator overloading a  +  b      //  a.plus(b)   a  -­‐  b      //  a.minus(b)   a  *  b      //  a.multiply(b)   a  /  b      //  a.div(b)   a  %  b      //  a.modulo(b)   a  **  b    //  a.power(b)   a  |  b      //  a.or(b)   a  &  b      //  a.and(b)   a  ^  b      //  a.xor(b)   a[b]        //  a.getAt(b)   a  <<  b    //  a.leftShift(b)   a  >>  b    //  a.rightShift(b)   a  >>>  b  //  a.rightShiftUnsigned(b)   +a            //  a.unaryPlus()   -­‐a            //  a.unaryMinus()   ~a            //  a.bitwiseNegate() @glaforge — @smaldini / #DV13-rtweb !70
Operator overloading a  +  b      //  a.plus(b)   a  -­‐  b      //  a.minus(b)   a  *  b      //  a.multiply(b)   Operator overloading is a  /  b      //  a.div(b)   a  %  b      //  a.modulo(b)   just a convention on a  **  b    //  a.power(b)   method names a  |  b      //  a.or(b)   a  &  b      //  a.and(b)   a  ^  b      //  a.xor(b)   a[b]        //  a.getAt(b)   a  <<  b    //  a.leftShift(b)   a  >>  b    //  a.rightShift(b)   a  >>>  b  //  a.rightShiftUnsigned(b)   +a            //  a.unaryPlus()   -­‐a            //  a.unaryMinus()   ~a            //  a.bitwiseNegate() @glaforge — @smaldini / #DV13-rtweb !70
Power asserts def  (a,  b,  c)  =  [20,  30,  40]   ! assert  a  *  (b  -­‐  1)  /  10  ==  3  *  c  /  2  +  1 @glaforge — @smaldini / #DV13-rtweb !71
Power asserts def  (a,  b,  c)  =  [20,  30,  40]   ! assert  a  *  (b  -­‐  1)  /  10  ==  3  *  c  /  2  +  1 Assertion  failed:     ! assert  a  *  (b  -­‐  1)  /  10  ==  3  *  c  /  2  +  1                |  |    |  |        |        |        |  |  |      |                |  580|  29      58      false|  |  60    61                20      30                              |  40                                                            120   !   at  script1.run(script1.groovy:3) @glaforge — @smaldini / #DV13-rtweb !71
Power asserts def  (a,  b,  c)  =  [20,  30,  40]   ! assert  a  *  (b  -­‐  1)  /  10  ==  3  *  c  /  2  +  1 Assertion  failed:     ! assert  a  *  (b  -­‐  1)  /  10  ==  3  *  c  /  2  +  1                |  |    |  |        |        |        |  |  |      |                |  580|  29      58      false|  |  60    61                20      30                              |  40                                                            120   ! Invented by the Spock testing framework   at  script1.run(script1.groovy:3) @glaforge — @smaldini / #DV13-rtweb !71
Null handling class  Order  {          LineItem  line   }   class  LineItem  {          int  quantity          Item  item   }   class  Item  {          String  name   }   ! def  o  =  new  Order(          line:  new  LineItem(                  quantity:  2,                  item:  null))   ! println  o.line.item.name @glaforge — @smaldini / #DV13-rtweb !72
Null handling class  Order  {          LineItem  line   }   class  LineItem  {          int  quantity          Item  item   }   class  Item  {          String  name   }   ! def  o  =  new  Order(          line:  new  LineItem(                  quantity:  2,                  item:  null))   With Java, you only get an NPE. No idea where it came from! ! println  o.line.item.name @glaforge — @smaldini / #DV13-rtweb !72
Null handling class  Order  {          LineItem  line   }   class  LineItem  {          int  quantity          Item  item   }   class  Item  {          String  name   }   ! def  o  =  new  Order(          line:  new  LineItem(                  quantity:  2,                  item:  null))   ! println  o.line.item.name @glaforge — @smaldini / #DV13-rtweb With Java, you only get an NPE. No idea where it came from! Groovy will say: Cannot get property ‘name’ on null object !72
Null handling class  Order  {          LineItem  line   }   class  LineItem  {          int  quantity          Item  item   }   class  Item  {          String  name   }   ! def  o  =  new  Order(          line:  new  LineItem(                  quantity:  2,                  item:  null))   ! println  o.line.item.name @glaforge — @smaldini / #DV13-rtweb !72
Null handling class  Order  {          LineItem  line   }   class  LineItem  {          int  quantity          Item  item   }   class  Item  {          String  name   }   o?.line?.item?.name ! def  o  =  new  Order(          line:  new  LineItem(                  quantity:  2,                  item:  null))   ! println  o.line.item.name @glaforge — @smaldini / #DV13-rtweb !72
Null handling class  Order  {          LineItem  line   }   class  LineItem  {          int  quantity          Item  item   }   class  Item  {          String  name   }   o?.line?.item?.name Safe navigation: will just return null; No NPE ! def  o  =  new  Order(          line:  new  LineItem(                  quantity:  2,                  item:  null))   ! println  o.line.item.name @glaforge — @smaldini / #DV13-rtweb !72
The Truth, the Groovy Truth!
The Truth, the Groovy Truth! And what if I could customize the truth?
The Groovy Truth assert  !(  null  )   assert  !(    ""    )   assert  !(    []    )   assert  !(      0    ) assert  new  Object()   assert  "string"   assert  [1,  2,  3]   assert  1234 @glaforge — @smaldini / #DV13-rtweb !74
The Groovy Truth null, empty, 0-sized, zero are coerced to false assert  !(  null  )   assert  !(    ""    )   assert  !(    []    )   assert  !(      0    ) assert  new  Object()   assert  "string"   assert  [1,  2,  3]   assert  1234 @glaforge — @smaldini / #DV13-rtweb !74
The Groovy Truth null, empty, 0-sized, zero are coerced to false assert  !(  null  )   assert  !(    ""    )   assert  !(    []    )   assert  !(      0    ) assert  new  Object()   assert  "string"   assert  [1,  2,  3]   assert  1234 @glaforge — @smaldini / #DV13-rtweb true otherwise !74
Customizing the truth! class  Account  {          String  name          boolean  disabled  =  false   !        boolean  asBoolean()  {  !disabled  }   }   ! assert    new  Account(name:  'current')   assert  !new  Account(name:  'old',  disabled:  true) @glaforge — @smaldini / #DV13-rtweb !75
Customizing the truth! class  Account  {          String  name          boolean  disabled  =  false   !        boolean  asBoolean()  {  !disabled  }   }   ! assert    new  Account(name:  'current')   assert  !new  Account(name:  'old',  disabled:  true) while (account), if (account), etc… @glaforge — @smaldini / #DV13-rtweb !75
?:
?: The Elvis operator!
Towards Elvis... @glaforge — @smaldini / #DV13-rtweb !77
Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] @glaforge — @smaldini / #DV13-rtweb !77
Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] @glaforge — @smaldini / #DV13-rtweb !77
Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] if  (x  !=  null  &&  x.size()  >  0)  x  else  y @glaforge — @smaldini / #DV13-rtweb !77
Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] if  (x  !=  null  &&  x.size()  >  0)  x  else  y if  (x  &&  x.size())  x  else  y @glaforge — @smaldini / #DV13-rtweb !77
Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] if  (x  !=  null  &&  x.size()  >  0)  x  else  y if  (x  &&  x.size())  x  else  y if  (x)  x  else  y @glaforge — @smaldini / #DV13-rtweb !77
Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] if  (x  !=  null  &&  x.size()  >  0)  x  else  y if  (x  &&  x.size())  x  else  y if  (x)  x  else  y x  ?  x  :  y @glaforge — @smaldini / #DV13-rtweb !77
Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] if  (x  !=  null  &&  x.size()  >  0)  x  else  y if  (x  &&  x.size())  x  else  y if  (x)  x  else  y x  ?  x  :  y x  ?:  y @glaforge — @smaldini / #DV13-rtweb !77
Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] if  (x  !=  null  &&  x.size()  >  0)  x  else  y if  (x  &&  x.size())  x  else  y if  (x)  x  else  y x  ?  x  :  y x  ?:  y Null, empty, zerosized... false, otherwise true! @glaforge — @smaldini / #DV13-rtweb !77
Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] if  (x  !=  null  &&  x.size()  >  0)  x  else  y if  (x  &&  x.size())  x  else  y if  (x)  x  else  y x  ?  x  :  y x  ?:  y Good old ternary operator @glaforge — @smaldini / #DV13-rtweb Null, empty, zerosized... false, otherwise true! !77
Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] if  (x  !=  null  &&  x.size()  >  0)  x  else  y if  (x  &&  x.size())  x  else  y if  (x)  x  else  y x  ?  x  :  y x  ?:  y Elvis! @glaforge — @smaldini / #DV13-rtweb Good old ternary operator Null, empty, zerosized... false, otherwise true! !77
AST transformations • Abstract Syntax Tree – in memory representation of your program
 before being compiled into bytecode ! • AST transformation == process of transforming the AST of a program before it’s compiled ! • Macro-like compiler hook! @glaforge — @smaldini / #DV13-rtweb !78
Lots of AST transformations... • Code generation – @ToString, @EqualsAndHashCode, @Canonical, @TupleConstructor, @InheritConstructors, @Category, @IndexedProperty, @Lazy, @Newify • Class design – @Delegate, @Immutable, @Memoized, 
 @Singleton, @Mixin • Logging – @Log, @Log4j, @Log4j2, @Slf4j @glaforge — @smaldini / #DV13-rtweb !79
Lots of AST transformations... • Safer scripting – @ConditionalInterrupt, @ThreadInterrupt, @TimedInterupt • Compiler directives – @Field, @PackageScope, @AnnotationCollector, @DelegatesTo, @TypeChecked, @CompileStatic, @CompileDynamic • Swing patterns – @Bindable, @ListenerList, @Vetoable @glaforge — @smaldini / #DV13-rtweb !80
Lots of AST transformations... • Dependencies handling – @Grab, @GrabConfig, @GrabExclude, @GrabResolver • Test assistance – @NotYetImplemented, @ASTTest @glaforge — @smaldini / #DV13-rtweb !81
Immutability • Implement immutability 
 by the book ! – final class – tuple-style constructor – private final backing fields – defensive copying of collections – equals() and hashCode() methods – toString() method – ... @glaforge — @smaldini / #DV13-rtweb !82
Immutability • Implement immutability 
 by the book ! Can be error-prone to write immutable classes oneself! – final class – tuple-style constructor – private final backing fields – defensive copying of collections – equals() and hashCode() methods – toString() method – ... @glaforge — @smaldini / #DV13-rtweb !82
Immutability • A Person class with – a String name – an int age public final class Person {! private final String name;! private final int age;! ! ! ! ! ! ! public Person(String name, int age) {! this.name = name;! this.age = age;! }! public String getName() {! return name;! }! public int getAge() {! return age;! }! public int hashCode() {! return age + 31 * name.hashCode();! }! public boolean equals(Object other) {! if (other == null) {! return false;! }! if (this == other) {! return true;! }! if (Person.class != other.getClass()) {! return false;! }! Person otherPerson = (Person)other;! if (!name.equals(otherPerson.getName()) {! return false;! }! if (age != otherPerson.getAge()) {! return false;! }! return true;! }! public String toString() {! return "Person(" + name + ", " + age + ")";! }! }! @glaforge — @smaldini / #DV13-rtweb !83
Immutability • A Person class with – a String name – an int age public final class Person {! private final String name;! private final int age;! ! ! ! ! ! ! public Person(String name, int age) {! this.name = name;! this.age = age;! }! Damn verbose Java! public String getName() {! return name;! }! public int getAge() {! return age;! }! public int hashCode() {! return age + 31 * name.hashCode();! }! public boolean equals(Object other) {! if (other == null) {! return false;! }! if (this == other) {! return true;! }! if (Person.class != other.getClass()) {! return false;! }! Person otherPerson = (Person)other;! if (!name.equals(otherPerson.getName()) {! return false;! }! if (age != otherPerson.getAge()) {! return false;! }! return true;! }! public String toString() {! return "Person(" + name + ", " + age + ")";! }! }! @glaforge — @smaldini / #DV13-rtweb !83
Immutability • A Person class with – a String name – an int age public final class Person {! private final String name;! private final int age;! ! ! ! ! ! ! public Person(String name, int age) {! this.name = name;! this.age = age;! }! Damn verbose Java! public String getName() {! return name;! }! public int getAge() {! return age;! }! public int hashCode() {! return age + 31 * name.hashCode();! }! public boolean equals(Object other) {! if (other == null) {! return false;! }! if (this == other) {! return true;! }! if (Person.class != other.getClass()) {! return false;! }! Person otherPerson = (Person)other;! if (!name.equals(otherPerson.getName()) {! return false;! }! if (age != otherPerson.getAge()) {! return false;! }! return true;! }! Although it’s also a valid Groovy program! public String toString() {! return "Person(" + name + ", " + age + ")";! }! }! @glaforge — @smaldini / #DV13-rtweb !83
@Immutable import  groovy.transform.*   ! @Immutable   class  Person  {          String  name          int  age   } @glaforge — @smaldini / #DV13-rtweb !84
Memoization • Cache the result of previous invocations of closures or methods with the same set of argument values import  groovy.transform.*   ! @Memoized   long  fib(long  n)  {          if  (n  ==  0)  0          else  if  (n  ==  1)  1          else  fib(n  -­‐  1)  +  fib(n  -­‐  2)   }   ! println  fib(40) @glaforge — @smaldini / #DV13-rtweb !85
Memoization • Cache the result of previous invocations of closures or methods with the same set of argument values import  groovy.transform.*   Best applied to side-effect free functions ! @Memoized   long  fib(long  n)  {          if  (n  ==  0)  0          else  if  (n  ==  1)  1          else  fib(n  -­‐  1)  +  fib(n  -­‐  2)   }   ! println  fib(40) @glaforge — @smaldini / #DV13-rtweb !85
Groovy allows you to be lazy
Groovy allows you to be lazy The compiler will do the job for you
Groovy allows you to be lazy More concise, more readable code The compiler will do the job for you
Groovy allows you to be lazy More concise, more readable code The compiler will do the job for you Less stuff to maintain and worry about
@TypeChecked & @CompileStatic • Static type checking with @TypeChecked, throws compilation errors on... – typos in method and variable names – incompatible return types – wrong type assignments ! • Supports fine-grained type inference – « Least Upper Bound » – « Flow typing » @glaforge — @smaldini / #DV13-rtweb !87
@TypeChecked & @CompileStatic • Static type checking with @TypeChecked, throws compilation errors on... – typos in method and variable names – incompatible return types – wrong type assignments ! You can even extend the static type checker! • Supports fine-grained type inference – « Least Upper Bound » – « Flow typing » @glaforge — @smaldini / #DV13-rtweb !87
@TypeChecked & @CompileStatic • Static type checking with @TypeChecked, throws compilation errors on... – typos in method and variable names – incompatible return types – wrong type assignments ! You can even extend the static type checker! • Supports fine-grained type inference – « Least Upper Bound » – « Flow typing » @glaforge — @smaldini / #DV13-rtweb Type check DSLs or dynamic features! !87
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013
Groovy reactor grails realtime web devoxx 2013

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Groovy reactor grails realtime web devoxx 2013

  • 1. Groovy, Reactor, Grails 
 & the realtime web Guillaume Laforge 
 @glaforge ! Stéphane Maldini
 @smaldini !
  • 2. Stéphane Maldini Consultant and Reactor committer at . ! @smaldini
  • 5.
  • 7.
  • 9.
  • 10. Realtime web applications are about the « now »
  • 11.
  • 12. Show users live updates as they come
  • 13. Show users live updates as they come A « push » approach vs a « pull » approach
  • 14. Show users live updates as they come A « push » approach vs a « pull » approach Handle a big volume of events
  • 15. Show users live updates as they come A « push » approach vs a « pull » approach Handle a big volume of events React fast to new events
  • 16. Show users live updates as they come A « push » approach vs a « pull » approach Handle a big volume of events React fast to new events Use promises, events, streams to react fast and stream updates to users as they are ready
  • 17. Show users live updates as they come Avoid blocking and state A « push » approach vs a « pull » approach Handle a big volume of events React fast to new events Use promises, events, streams to react fast and stream updates to users as they are ready
  • 18. Show users live updates as they come Fail gracefully Avoid blocking and state A « push » approach vs a « pull » approach Handle a big volume of events React fast to new events Use promises, events, streams to react fast and stream updates to users as they are ready
  • 19.
  • 22. Groovy… an Open Source 
 alternative language 
 for the JVM
  • 24. Groovy… But also supports 
 static type checking & 
 static compilation
  • 26.
  • 27.
  • 29.
  • 30. Simplify the life of (Java) developers
  • 31.
  • 32. Groovy as a Java superset
  • 33. Groovy as a Java superset It’s so easy to learn!
  • 34.
  • 35.
  • 36.
  • 37. As safe and fast as Java with static type checking & compilation
  • 38. As safe and fast as Java with static type checking & compilation
  • 39.
  • 40. new  MarkupBuilder().html  {          head  {                  title  "The  Script  Bowl"          }   !        body  {                  div(class:  "banner")  {                          p  "Groovy  rocks!"                  }          }   }
  • 41.
  • 42. move  forward  at  3.km/h Expressive, Concise, Readable
  • 43.
  • 44.
  • 45. Speaking of conciseness... A full Spring app in the span of a tweet! @RestController   class  App  {          @RequestMapping("/")          String  home()  {  "Hello  World!"  }   }
  • 46.
  • 48. Great for scripting Fit for Domain-Specific Languages
  • 49. Great for scripting Fit for Domain-Specific Languages Most seamless integration & interoperability wih java!
  • 50. Great for scripting Full-blown reactive applications too! Fit for Domain-Specific Languages Most seamless integration & interoperability wih java!
  • 51.
  • 52. Most Java code is also valid Groovy code!
  • 53. Most Java code is also valid Groovy code! Any Java developer is a Groovy developer!
  • 54.
  • 57. Scripts versus Classes public  class  Main  {          public  static  void  main(String[]  args)  {                  System.out.println("Hello");          }   } vs @glaforge — @smaldini / #DV13-rtweb !26
  • 58. Scripts versus Classes public  class  Main  {          public  static  void  main(String[]  args)  {                  System.out.println("Hello");          }   } vs println  "Hello" @glaforge — @smaldini / #DV13-rtweb !26
  • 65. Optional... public  class  Greeter  {          private  String  owner;   !        public  String  getOwner()  {                  return  owner;          }   !        public  void  setOwner(String  owner)  {                  this.owner  =  owner;          }   !        public  String  greet(String  name)  {                  return  "Hello  "  +  name  +  ",  I  am  "  +  owner;          }   }   ! Greeter  greeter  =  new  Greeter();   greeter.setOwner("Guillaume");   ! System.out.println(greeter.greet("Marion")); @glaforge — @smaldini / #DV13-rtweb !28
  • 66. Optional... Semicolons public  class  Greeter  {          private  String  owner;   !        public  String  getOwner()  {                  return  owner;          }   !        public  void  setOwner(String  owner)  {                  this.owner  =  owner;          }   !        public  String  greet(String  name)  {                  return  "Hello  "  +  name  +  ",  I  am  "  +  owner;          }   }   ! Greeter  greeter  =  new  Greeter();   greeter.setOwner("Guillaume");   ! System.out.println(greeter.greet("Marion")); @glaforge — @smaldini / #DV13-rtweb !28
  • 67. Optional... public  class  Greeter  {          private  String  owner   !        public  String  getOwner()  {                  return  owner          }   !        public  void  setOwner(String  owner)  {                  this.owner  =  owner          }   !        public  String  greet(String  name)  {                  return  "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Greeter  greeter  =  new  Greeter()   greeter.setOwner("Guillaume")   ! System.out.println(greeter.greet("Marion")) @glaforge — @smaldini / #DV13-rtweb !29
  • 68. Optional... public  class  Greeter  {          private  String  owner   !        public  String  getOwner()  {                  return  owner          }   !        public  void  setOwner(String  owner)  {                  this.owner  =  owner          }   !        public  String  greet(String  name)  {                  return  "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Greeter  greeter  =  new  Greeter()   greeter.setOwner("Guillaume")   ! System.out.println(greeter.greet("Marion")) @glaforge — @smaldini / #DV13-rtweb !30
  • 69. Optional... public  class  Greeter  {          private  String  owner   !        public  String  getOwner()  {                  return  owner          }   !        public  void  setOwner(String  owner)  {                  this.owner  =  owner          }   !        public  String  greet(String  name)  {                  return  "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Greeter  greeter  =  new  Greeter()   greeter.setOwner("Guillaume")   Parentheses ! System.out.println(greeter.greet("Marion")) @glaforge — @smaldini / #DV13-rtweb !30
  • 70. Optional... public  class  Greeter  {          private  String  owner   !        public  String  getOwner()  {                  return  owner          }   !        public  void  setOwner(String  owner)  {                  this.owner  =  owner          }   !        public  String  greet(String  name)  {                  return  "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Greeter  greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   ! System.out.println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !31
  • 71. Optional... public  class  Greeter  {          private  String  owner   !        public  String  getOwner()  {                  return  owner          }   !        public  void  setOwner(String  owner)  {                  this.owner  =  owner          }   ! return keyword        public  String  greet(String  name)  {                  return  "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Greeter  greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   ! System.out.println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !31
  • 72. Optional... public  class  Greeter  {          private  String  owner   !        public  String  getOwner()  {                                owner          }   !        public  void  setOwner(String  owner)  {                  this.owner  =  owner          }   !        public  String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Greeter  greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   ! System.out.println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !32
  • 73. Optional... public  class  Greeter  {          private  String  owner   !        public  String  getOwner()  {                                owner          }   ! public keyword        public  void  setOwner(String  owner)  {                  this.owner  =  owner          }   !        public  String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Greeter  greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   ! System.out.println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !32
  • 74. Optional...              class  Greeter  {          private  String  owner   !                      String  getOwner()  {                                owner          }   !                      void  setOwner(String  owner)  {                  this.owner  =  owner          }   !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Greeter  greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   ! System.out.println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !33
  • 75. Optional...              class  Greeter  {          private  String  owner   !                      String  getOwner()  {                                owner          }   !                      void  setOwner(String  owner)  {                  this.owner  =  owner          }   !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   optional typing ! Greeter  greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   ! System.out.println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !33
  • 76. Optional...              class  Greeter  {          private  String  owner   !                      String  getOwner()  {                                owner          }   !                      void  setOwner(String  owner)  {                  this.owner  =  owner          }   !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! def          greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   ! System.out.println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !34
  • 77. Optional...              class  Greeter  {          private  String  owner   !                      String  getOwner()  {                                owner          }   !                      void  setOwner(String  owner)  {                  this.owner  =  owner          }   !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   handy println shortcut def          greeter  =  new  Greeter()   ! greeter.setOwner  "Guillaume"   ! System.out.println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !34
  • 78. Optional...              class  Greeter  {          private  String  owner   !                      String  getOwner()  {                                owner          }   !                      void  setOwner(String  owner)  {                  this.owner  =  owner          }   !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! def          greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !35
  • 79. Optional... verbose Java properties!              class  Greeter  {          private  String  owner   !                      String  getOwner()  {                                owner          }   !                      void  setOwner(String  owner)  {                  this.owner  =  owner          }   !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! def          greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !35
  • 80. Optional...              class  Greeter  {                          String  owner   ! ! ! ! ! ! ! ! !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! def          greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !36
  • 81. Optional...              class  Greeter  {                          String  owner   ! ! ! ! ! ! ! ! !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! Property notation def          greeter  =  new  Greeter()   greeter.setOwner  "Guillaume"   !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !36
  • 82. Optional...              class  Greeter  {                          String  owner   ! ! ! ! ! ! ! ! !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! def          greeter  =  new  Greeter()   greeter.owner  =    "Guillaume"   !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !37
  • 83. Optional...              class  Greeter  {                          String  owner   ! ! ! ! ! ! ! ! Named argument                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner   constructor !        }   }   ! def          greeter  =  new  Greeter()   greeter.owner  =    "Guillaume"   !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !37
  • 84. Optional...              class  Greeter  {                          String  owner   ! ! ! ! ! ! ! ! !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! def          greeter  =  new  Greeter(owner:  "Guillaume")   ! !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !38
  • 85. Optional...              class  Greeter  {                          String  owner   ! ! ! ! ! ! Interpolated strings! (aka GStrings) ! ! !                      String  greet(String  name)  {                                "Hello  "  +  name  +  ",  I  am  "  +  owner          }   }   ! def          greeter  =  new  Greeter(owner:  "Guillaume")   ! !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !38
  • 86. Optional...              class  Greeter  {                          String  owner   ! ! ! ! ! ! ! ! !                      String  greet(String  name)  {                                "Hello  ${name},  I  am  ${owner}"          }   }   ! def          greeter  =  new  Greeter(owner:  "Guillaume")   ! !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !39
  • 87. Optional...              class  Greeter  {                          String  owner   ! ! ! ! Let’s reformat that mess of whitespace! ! ! ! ! !                      String  greet(String  name)  {                                "Hello  ${name},  I  am  ${owner}"          }   }   ! def          greeter  =  new  Greeter(owner:  "Guillaume")   ! !                      println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !39
  • 88. Optional... class  Greeter  {          String  owner   !        String  greet(String  name)  {                "Hello  ${name},  I  am  ${owner}"          }   }   ! def  greeter  =  new  Greeter(owner:  "Guillaume")   ! println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !40
  • 89. Optional... public  class  Greeter  {          private  String  owner;   !        public  String  getOwner()  {   class  Greeter  {                  return  owner;          String  owner          }   ! !        String  greet(String  name)  {          public  void  setOwner(String  owner)  {                "Hello  ${name},  I  am  ${owner}"                  this.owner  =  owner;          }          }   }   ! !        public  String  greet(String  name)  {   def  greeter  =  new  Greeter(owner:  "Guillaume")                  return  "Hello  "  +  name  +  ",  I  am  "  +  owner;   !        }   println  greeter.greet("Marion") }   ! Greeter  greeter  =  new  Greeter();   greeter.setOwner("Guillaume");   ! System.out.println(greeter.greet("Marion")); @glaforge — @smaldini / #DV13-rtweb !40
  • 90. Optional... class  Greeter  {          String  owner   !        String  greet(String  name)  {                "Hello  ${name},  I  am  ${owner}"          }   }   ! def  greeter  =  new  Greeter(owner:  "Guillaume")   ! println  greeter.greet("Marion") @glaforge — @smaldini / #DV13-rtweb !40
  • 91. Native syntax constructs //  closures   def  adder  =  {  a,  b  -­‐>  a  +  b  }   ! //  lists   def  list  =  [1,  2,  3,  4,  5]   ! //  maps   def  map  =  [a:  1,  b:  2,  c:  3]   ! //  regular  expressions   def  regex  =  ~/.*foo.*/   ! //  ranges   def  range  128..255 @glaforge — @smaldini / #DV13-rtweb !41
  • 92. Closures — the basics • Functions as first-class citizen of the language def  adder  =  {  a,  b  -­‐>  a  +  b  }   ! assert  adder(1,  2)  ==  3   assert  adder('a',  'b')  ==  'ab' @glaforge — @smaldini / #DV13-rtweb !42
  • 93. Closures — the basics • Functions as first-class citizen of the language Closure parameters def  adder  =  {  a,  b  -­‐>  a  +  b  }   ! assert  adder(1,  2)  ==  3   assert  adder('a',  'b')  ==  'ab' @glaforge — @smaldini / #DV13-rtweb !42
  • 94. Closures — the basics • Functions as first-class citizen of the language Assign a function Closure into a variable parameters def  adder  =  {  a,  b  -­‐>  a  +  b  }   ! assert  adder(1,  2)  ==  3   assert  adder('a',  'b')  ==  'ab' @glaforge — @smaldini / #DV13-rtweb !42
  • 95. Closures — the basics • Functions as first-class citizen of the language Assign a function Closure into a variable parameters def  adder  =  {  a,  b  -­‐>  a  +  b  }   ! assert  adder(1,  2)  ==  3   assert  adder('a',  'b')  ==  'ab' Short form of: adder.call(‘a’, ‘b’) @glaforge — @smaldini / #DV13-rtweb !42
  • 96. Closures — the basics • Functions as first-class citizen of the language Assign a function Closure into a variable parameters def  adder  =  {  a,  b  -­‐>  a  +  b  }   ! assert  adder(1,  2)  ==  3   assert  adder('a',  'b')  ==  'ab' Short form of: adder.call(‘a’, ‘b’) @glaforge — @smaldini / #DV13-rtweb Genericity with duck typing & operator overloading !42
  • 97. Closures — explicit type ! def  intAdder  =  {  int  a,  int  b  -­‐>  a  +  b  } @glaforge — @smaldini / #DV13-rtweb !43
  • 98. Closures — explicit type Be explicit about the types ! def  intAdder  =  {  int  a,  int  b  -­‐>  a  +  b  } @glaforge — @smaldini / #DV13-rtweb !43
  • 99. Closures — implicit parameter def  doubler  =  {  it  *  2  }   ! assert  doubler(3)  ==  6   assert  doubler('a')  ==  'aa' @glaforge — @smaldini / #DV13-rtweb !44
  • 100. Closures — implicit parameter Implicit parameter def  doubler  =  {  it  *  2  }   ! assert  doubler(3)  ==  6   assert  doubler('a')  ==  'aa' @glaforge — @smaldini / #DV13-rtweb !44
  • 101. Closures — implicit parameter Implicit parameter def  doubler  =  {  it  *  2  }   ! assert  doubler(3)  ==  6   assert  doubler('a')  ==  'aa' Multiply also defined on strings @glaforge — @smaldini / #DV13-rtweb !44
  • 102. Closures — variable arguments def  sum  =  {  ...  elements  -­‐>  
                                elements.sum()  }   ! assert  sum(1,  2)  ==  3   assert  sum('a',  'b',  'c')  ==  'abc' @glaforge — @smaldini / #DV13-rtweb !45
  • 103. Closures — variable arguments Variable number of arguments def  sum  =  {  ...  elements  -­‐>  
                                elements.sum()  }   ! assert  sum(1,  2)  ==  3   assert  sum('a',  'b',  'c')  ==  'abc' @glaforge — @smaldini / #DV13-rtweb !45
  • 104. Closures — variable arguments You can specify the type: int... Variable number of arguments def  sum  =  {  ...  elements  -­‐>  
                                elements.sum()  }   ! assert  sum(1,  2)  ==  3   assert  sum('a',  'b',  'c')  ==  'abc' @glaforge — @smaldini / #DV13-rtweb !45
  • 105. Closures — default values def  mult  =  {  int  a,  int  b  =  10  -­‐>  a  *  b  }   ! assert  mult(2,  3)  ==  6   assert  mult(5)  ==  50 @glaforge — @smaldini / #DV13-rtweb !46
  • 106. Closures — default values Default value def  mult  =  {  int  a,  int  b  =  10  -­‐>  a  *  b  }   ! assert  mult(2,  3)  ==  6   assert  mult(5)  ==  50 @glaforge — @smaldini / #DV13-rtweb !46
  • 107. Closures — default values Default value def  mult  =  {  int  a,  int  b  =  10  -­‐>  a  *  b  }   ! assert  mult(2,  3)  ==  6   assert  mult(5)  ==  50 @glaforge — @smaldini / #DV13-rtweb Provided value for b !46
  • 108. Closures — default values Default value def  mult  =  {  int  a,  int  b  =  10  -­‐>  a  *  b  }   ! assert  mult(2,  3)  ==  6   assert  mult(5)  ==  50 Default value used for b @glaforge — @smaldini / #DV13-rtweb Provided value for b !46
  • 109. Closures — methods as functions def  logBase10  =  Math.&log10   def  printer  =  System.out.&println   ! assert  logBase10(10)  ==  1   printer  'abc' @glaforge — @smaldini / #DV13-rtweb !47
  • 110. Closures — methods as functions Turn a method into a closure function def  logBase10  =  Math.&log10   def  printer  =  System.out.&println   ! assert  logBase10(10)  ==  1   printer  'abc' @glaforge — @smaldini / #DV13-rtweb !47
  • 111. Closures — map / filter / reduce @glaforge — @smaldini / #DV13-rtweb !48
  • 112. Closures — map / filter / reduce @groovy.transform.Immutable
 class  Person  {
        String  name
        int  age
 } @glaforge — @smaldini / #DV13-rtweb !48
  • 113. Closures — map / filter / reduce @groovy.transform.Immutable
 class  Person  {
        String  name
        int  age
 } @glaforge — @smaldini / #DV13-rtweb !48
  • 114. Closures — map / filter / reduce @groovy.transform.Immutable
 class  Person  {
        String  name
        int  age
 } def  persons  =  [
        new  Person('Guillaume',  36),
        new  Person('Marion',  5),
        new  Person('Erine',  1)
 ] @glaforge — @smaldini / #DV13-rtweb !48
  • 115. Closures — map / filter / reduce @groovy.transform.Immutable
 class  Person  {
        String  name
        int  age
 } def  persons  =  [
        new  Person('Guillaume',  36),
        new  Person('Marion',  5),
        new  Person('Erine',  1)
 ] @glaforge — @smaldini / #DV13-rtweb !48
  • 116. Closures — map / filter / reduce @groovy.transform.Immutable
 class  Person  {
        String  name
        int  age
 } def  persons  =  [
        new  Person('Guillaume',  36),
        new  Person('Marion',  5),
        new  Person('Erine',  1)
 ] def  names  =
        persons.findAll  {  it.age  <  18  }
                      .collect  {  it.name.toUpperCase()  }
                      .sort()
                      .join(',  ') @glaforge — @smaldini / #DV13-rtweb !48
  • 117. Closures — map / filter / reduce @groovy.transform.Immutable
 class  Person  {
        String  name
        int  age
 } def  persons  =  [
        new  Person('Guillaume',  36),
        new  Person('Marion',  5),
        new  Person('Erine',  1)
 ] def  names  =
        persons.findAll  {  it.age  <  18  }
                      .collect  {  it.name.toUpperCase()  }
                      .sort()
                      .join(',  ') @glaforge — @smaldini / #DV13-rtweb !48
  • 118. Closures — map / filter / reduce @groovy.transform.Immutable
 class  Person  {
        String  name
        int  age
 } def  persons  =  [
        new  Person('Guillaume',  36),
        new  Person('Marion',  5),
        new  Person('Erine',  1)
 ] def  names  =
        persons.findAll  {  it.age  <  18  }
                      .collect  {  it.name.toUpperCase()  }
                      .sort()
                      .join(',  ') assert  names  ==  "ERINE,  MARION" @glaforge — @smaldini / #DV13-rtweb !48
  • 119. Closures — map / filter / reduce @groovy.transform.Immutable
 class  Person  {
        String  name
        int  age
 } def  persons  =  [
        new  Person('Guillaume',  36),
        new  Person('Marion',  5),
        new  Person('Erine',  1)
 ] find/findAll, inject, collect, flatten, min/max, unique, reverse, collate, groupBy, any/every, head/tail/last, count/countBy, combinations/ permutations/subsequences/ transpose, withDefault/ withLazyDefault def  names  =
        persons.findAll  {  it.age  <  18  }
                      .collect  {  it.name.toUpperCase()  }
                      .sort()
                      .join(',  ') assert  names  ==  "ERINE,  MARION" @glaforge — @smaldini / #DV13-rtweb !48
  • 120. Closures — resource handling new  File('bible.txt').withReader  {  r  -­‐>          new  File('out.txt').withWriter  {  w  -­‐>                  r.eachLine  {  line  -­‐>                          if  (line.contains('Groovy'))                                  w  <<  line.toUpperCase()                  }          }   } @glaforge — @smaldini / #DV13-rtweb !49
  • 121. Closures — resource handling Take care of properly opening / closing resources new  File('bible.txt').withReader  {  r  -­‐>          new  File('out.txt').withWriter  {  w  -­‐>                  r.eachLine  {  line  -­‐>                          if  (line.contains('Groovy'))                                  w  <<  line.toUpperCase()                  }          }   } @glaforge — @smaldini / #DV13-rtweb !49
  • 122. Closures — custom control structures void  unless(boolean  cond,  Closure  c)  {          if  (!cond)  c()   }   ! unless  (10  <  9)  {          println  "less"   } @glaforge — @smaldini / #DV13-rtweb !50
  • 123. Closures — custom control structures Closure as last argument void  unless(boolean  cond,  Closure  c)  {          if  (!cond)  c()   }   ! unless  (10  <  9)  {          println  "less"   } @glaforge — @smaldini / #DV13-rtweb !50
  • 124. Closures — custom control structures Closure as last argument void  unless(boolean  cond,  Closure  c)  {          if  (!cond)  c()   }   ! unless  (10  <  9)  {          println  "less"   } @glaforge — @smaldini / #DV13-rtweb Equivalent to: unless(10<9, {...}) !50
  • 125. Closures — custom control structures class  Reactor  {            void  on(Selector  s,  Closure  c)  {  …  }   }   …   reactor.on(  $(‘abc')  )  {  Event<String>  ev  -­‐>          …   } @glaforge — @smaldini / #DV13-rtweb !51
  • 126. Closures — builders leverage closures import  groovy.json.*   ! def  json  =  new  JsonBuilder()   json.person  {          name  'Guillaume'          age  36          daughters  'Marion',  'Erine'          address  {                  street  '1  Main  Street'                  zip  75001                  city  'Paris'          }   } @glaforge — @smaldini / #DV13-rtweb !52
  • 127. Closures — builders leverage closures import  groovy.json.*   ! def  json  =  new  JsonBuilder()   json.person  {          name  'Guillaume'          age  36          daughters  'Marion',  'Erine'          address  {                  street  '1  Main  Street'                  zip  75001                  city  'Paris'          }   } @glaforge — @smaldini / #DV13-rtweb Hierarchical data representation !52
  • 128. Closures — builders leverage closures import  groovy.json.*   ! Hierarchical data representation def  json  =  new  JsonBuilder()   json.person  {          name  'Guillaume'          age  36   Closure blocks        daughters  'Marion',  'Erine'   delimiting the        address  {   structure                street  '1  Main  Street'                  zip  75001                  city  'Paris'          }   } @glaforge — @smaldini / #DV13-rtweb !52
  • 129. Closures — builders leverage closures import  groovy.json.*   {          "person":  {   Hierarchical data def  json  =  new  JsonBuilder()                  "name":  "Guillaume",   representation                "age":  36,   json.person  {                  "daughters":  [          name  'Guillaume'                          "Marion",                          "Erine"          age  36                  ],   Closure blocks        daughters  'Marion',  'Erine'                  "address":  {   delimiting the                        "street":  "1  Main  Street",          address  {                          "zip":  75001,   structure                street  '1  Main  Street'                          "city":  "Paris"                  }                  zip  75001          }                  city  'Paris'   } !        }   } @glaforge — @smaldini / #DV13-rtweb !52
  • 130. Closure — your own builders GroovyEnvironment.create  {          environment  {                  defaultDispatcher  =  "test"   !                dispatcher('test')  {                          type  =  DispatcherType.SYNCHRONOUS                  }          }   } @glaforge — @smaldini / #DV13-rtweb !53
  • 131. Closure — your own builders GroovyEnvironment.create  {          environment  {                  defaultDispatcher  =  "test"   !                dispatcher('test')  {                          type  =  DispatcherType.SYNCHRONOUS                  }          }   } @glaforge — @smaldini / #DV13-rtweb !53
  • 132. Closure — your own builders GroovyEnvironment.create  {          environment  {                  defaultDispatcher  =  "test"   !                dispatcher('test')  {                          type  =  DispatcherType.SYNCHRONOUS                  }          }   } @glaforge — @smaldini / #DV13-rtweb !53
  • 133. Closure — your own builders GroovyEnvironment.create  {          environment  {                  defaultDispatcher  =  "test"   !                dispatcher('test')  {                          type  =  DispatcherType.SYNCHRONOUS                  }          }   } @glaforge — @smaldini / #DV13-rtweb !53
  • 134. Closure — your own builders GroovyEnvironment.create  {          environment  {                  defaultDispatcher  =  "test"   !                dispatcher('test')  {                          type  =  DispatcherType.SYNCHRONOUS                  }          }   } @glaforge — @smaldini / #DV13-rtweb !53
  • 135. Closure — your own builders Implement a builder extending BuilderSupport or FactoryBuilderSupport… GroovyEnvironment.create  {   or roll your own!        environment  {                  defaultDispatcher  =  "test"   !                dispatcher('test')  {                          type  =  DispatcherType.SYNCHRONOUS                  }          }   } @glaforge — @smaldini / #DV13-rtweb !53
  • 136. Closure — your own builders Implement a builder extending BuilderSupport or FactoryBuilderSupport… GroovyEnvironment.create  {   or roll your own!        environment  {                  defaultDispatcher  =  "test"   abstract  class  BuilderSupport  {          abstract  void  setParent(Object  parent,  Object  child)   !        abstract  Object  createNode(Object  name)                  dispatcher('test')  {          abstract  Object  createNode(Object  name,  Object  value)          abstract  Object  createNode(Object  name,  Map  attributes)                          type  =  DispatcherType.SYNCHRONOUS          abstract  Object  createNode(Object  name,  Map  attributes,  Object  value)   }                  }          }   } @glaforge — @smaldini / #DV13-rtweb !53
  • 137. GPath expressions • GPath expressions are like XPath 
 but for an object graph import  groovy.json.*   ! def  url  =  "https://api.github.com/repos/groovy/groovy-­‐core/commits"   ! def  commits  =  new  JsonSlurper().parseText(url.toURL().text)   ! assert  commits[0].commit.author.name  ==  'Cedric  Champeau' @glaforge — @smaldini / #DV13-rtweb !54
  • 138. GPath expressions • GPath expressions are like XPath 
 but for an object graph import  groovy.json.*   ! def  url  =  "https://api.github.com/repos/groovy/groovy-­‐core/commits"   ! def  commits  =  new  JsonSlurper().parseText(url.toURL().text)   ! assert  commits[0].commit.author.name  ==  'Cedric  Champeau' GPath expression @glaforge — @smaldini / #DV13-rtweb !54
  • 139. GPath expressions • GPath expressions are like XPath 
 but for an object graph import  groovy.json.*   ! def  url  =  "https://api.github.com/repos/groovy/groovy-­‐core/commits"   ! def  commits  =  new  JsonSlurper().parseText(url.toURL().text)   ! assert  commits[0].commit.author.name  ==  'Cedric  Champeau' GPath expression @glaforge — @smaldini / #DV13-rtweb Add find / findAll into the mix !54
  • 140. GPath expressions • GPath expressions are like XPath 
 but for an object graph No (un)marshalling! import  groovy.json.*   ! def  url  =  "https://api.github.com/repos/groovy/groovy-­‐core/commits"   ! def  commits  =  new  JsonSlurper().parseText(url.toURL().text)   ! assert  commits[0].commit.author.name  ==  'Cedric  Champeau' GPath expression @glaforge — @smaldini / #DV13-rtweb Add find / findAll into the mix !54
  • 141. Lists def  list  =  ['a',  'b',  'c']   ! list  <<  'd'   assert  list.contains('d')   ! assert  list.findAll  {  it.startsWith  'a'  }.size()  ==  1   assert  list.collect  {  it.toUpperCase()  }  
                                                              ==  ['A',  'B',  'C',  'D']   assert  list.inject('')  {  a,  b  -­‐>  a  +  b  }  ==  'abcd' @glaforge — @smaldini / #DV13-rtweb !55
  • 142. Lists List definition def  list  =  ['a',  'b',  'c']   ! list  <<  'd'   assert  list.contains('d')   ! assert  list.findAll  {  it.startsWith  'a'  }.size()  ==  1   assert  list.collect  {  it.toUpperCase()  }  
                                                              ==  ['A',  'B',  'C',  'D']   assert  list.inject('')  {  a,  b  -­‐>  a  +  b  }  ==  'abcd' @glaforge — @smaldini / #DV13-rtweb !55
  • 143. Lists List definition def  list  =  ['a',  'b',  'c']   ! list  <<  'd'   assert  list.contains('d')   Append an element (operator overloading) ! assert  list.findAll  {  it.startsWith  'a'  }.size()  ==  1   assert  list.collect  {  it.toUpperCase()  }  
                                                              ==  ['A',  'B',  'C',  'D']   assert  list.inject('')  {  a,  b  -­‐>  a  +  b  }  ==  'abcd' @glaforge — @smaldini / #DV13-rtweb !55
  • 144. Lists List definition def  list  =  ['a',  'b',  'c']   ! list  <<  'd'   assert  list.contains('d')   Append an element (operator overloading) ! assert  list.findAll  {  it.startsWith  'a'  }.size()  ==  1   assert  list.collect  {  it.toUpperCase()  }  
                                                              ==  ['A',  'B',  'C',  'D']   assert  list.inject('')  {  a,  b  -­‐>  a  +  b  }  ==  'abcd' Functional-style map / filter / reduce with closures @glaforge — @smaldini / #DV13-rtweb !55
  • 145. Maps def  map  =  [name:  'Guillaume',  age:  36]   ! map.daughters  =  ['Marion',  'Erine']   ! assert  map['daughters'].contains('Marion') @glaforge — @smaldini / #DV13-rtweb !56
  • 146. Maps Map definition def  map  =  [name:  'Guillaume',  age:  36]   ! map.daughters  =  ['Marion',  'Erine']   ! assert  map['daughters'].contains('Marion') @glaforge — @smaldini / #DV13-rtweb !56
  • 147. Maps Map definition def  map  =  [name:  'Guillaume',  age:  36]   ! map.daughters  =  ['Marion',  'Erine']   ! assert  map['daughters'].contains('Marion') Indexed access @glaforge — @smaldini / #DV13-rtweb !56
  • 148. Maps Map definition def  map  =  [name:  'Guillaume',  age:  36]   ! map.daughters  =  ['Marion',  'Erine']   ! assert  map['daughters'].contains('Marion') Property notation access @glaforge — @smaldini / #DV13-rtweb Indexed access !56
  • 149. Regular expressions def  pattern  =  ~/.*foo.*/   ! assert  "Alibaba"  ==~  /.*(ba){2}/   ! def  matcher  =  "Superman"  =~  /([A-­‐Z][a-­‐z]+)man/   assert  matcher[0][0]  ==  'Superman'   assert  matcher[0][1]  ==  'Super'   ! '75001  Paris'.find(/(d{5})s(w+)/)  {  match,  zip,  town  -­‐>          println  "The  Zip  code  of  ${town}  is  ${zip}"   } @glaforge — @smaldini / #DV13-rtweb !57
  • 150. Regular expressions Pattern def  pattern  =  ~/.*foo.*/   ! assert  "Alibaba"  ==~  /.*(ba){2}/   ! def  matcher  =  "Superman"  =~  /([A-­‐Z][a-­‐z]+)man/   assert  matcher[0][0]  ==  'Superman'   assert  matcher[0][1]  ==  'Super'   ! '75001  Paris'.find(/(d{5})s(w+)/)  {  match,  zip,  town  -­‐>          println  "The  Zip  code  of  ${town}  is  ${zip}"   } @glaforge — @smaldini / #DV13-rtweb !57
  • 151. Regular expressions Pattern def  pattern  =  ~/.*foo.*/   Match ! assert  "Alibaba"  ==~  /.*(ba){2}/   ! def  matcher  =  "Superman"  =~  /([A-­‐Z][a-­‐z]+)man/   assert  matcher[0][0]  ==  'Superman'   assert  matcher[0][1]  ==  'Super'   ! '75001  Paris'.find(/(d{5})s(w+)/)  {  match,  zip,  town  -­‐>          println  "The  Zip  code  of  ${town}  is  ${zip}"   } @glaforge — @smaldini / #DV13-rtweb !57
  • 152. Regular expressions Pattern def  pattern  =  ~/.*foo.*/   Match ! assert  "Alibaba"  ==~  /.*(ba){2}/   Find ! def  matcher  =  "Superman"  =~  /([A-­‐Z][a-­‐z]+)man/   assert  matcher[0][0]  ==  'Superman'   assert  matcher[0][1]  ==  'Super'   ! '75001  Paris'.find(/(d{5})s(w+)/)  {  match,  zip,  town  -­‐>          println  "The  Zip  code  of  ${town}  is  ${zip}"   } @glaforge — @smaldini / #DV13-rtweb !57
  • 153. Regular expressions Pattern def  pattern  =  ~/.*foo.*/   Match ! assert  "Alibaba"  ==~  /.*(ba){2}/   Find ! def  matcher  =  "Superman"  =~  /([A-­‐Z][a-­‐z]+)man/   assert  matcher[0][0]  ==  'Superman'   assert  matcher[0][1]  ==  'Super'   ! '75001  Paris'.find(/(d{5})s(w+)/)  {  match,  zip,  town  -­‐>          println  "The  Zip  code  of  ${town}  is  ${zip}"   } Nice way to decompose the matched regions @glaforge — @smaldini / #DV13-rtweb !57
  • 154. Ranges def  range  =  'a'..'z'   ! assert  range.contains('m')   assert  range.contains('z')   ! def  exclusive  =  1..<10   ! assert  !exclusive.contains(10)   ! def  reverse  =  10..0   ! assert  reverse[0]  ==  10   assert  reverse[-­‐1]  ==  0 @glaforge — @smaldini / #DV13-rtweb !58
  • 155. Ranges Range def  range  =  'a'..'z'   ! assert  range.contains('m')   assert  range.contains('z')   ! def  exclusive  =  1..<10   ! assert  !exclusive.contains(10)   ! def  reverse  =  10..0   ! assert  reverse[0]  ==  10   assert  reverse[-­‐1]  ==  0 @glaforge — @smaldini / #DV13-rtweb !58
  • 156. Ranges Range def  range  =  'a'..'z'   ! assert  range.contains('m')   assert  range.contains('z')   ! def  exclusive  =  1..<10   Excluded upper bound ! assert  !exclusive.contains(10)   ! def  reverse  =  10..0   ! assert  reverse[0]  ==  10   assert  reverse[-­‐1]  ==  0 @glaforge — @smaldini / #DV13-rtweb !58
  • 157. Ranges Range def  range  =  'a'..'z'   ! assert  range.contains('m')   assert  range.contains('z')   ! def  exclusive  =  1..<10   Excluded upper bound ! assert  !exclusive.contains(10)   ! def  reverse  =  10..0   Reverse range ! assert  reverse[0]  ==  10   assert  reverse[-­‐1]  ==  0 @glaforge — @smaldini / #DV13-rtweb !58
  • 158. Ranges Range def  range  =  'a'..'z'   ! assert  range.contains('m')   assert  range.contains('z')   ! def  exclusive  =  1..<10   Excluded upper bound ! assert  !exclusive.contains(10)   ! def  reverse  =  10..0   Reverse range ! assert  reverse[0]  ==  10   assert  reverse[-­‐1]  ==  0 @glaforge — @smaldini / #DV13-rtweb Negative index count from the end !58
  • 159. Strings, GStrings, multiline strings def  name  =  'Groovy'   def  tmpl  =  """          Dear  Mr  ${name},          You're  the  winner  of  the  lottery!          Yours  sincerly,          Dave   """   ! assert  tmpl.toString().contains('Groovy') @glaforge — @smaldini / #DV13-rtweb !59
  • 160. Strings, GStrings, multiline strings Plain java.lang.String def  name  =  'Groovy'   def  tmpl  =  """          Dear  Mr  ${name},          You're  the  winner  of  the  lottery!          Yours  sincerly,          Dave   """   ! assert  tmpl.toString().contains('Groovy') @glaforge — @smaldini / #DV13-rtweb !59
  • 161. Strings, GStrings, multiline strings Plain java.lang.String def  name  =  'Groovy'   Multiline string with def  tmpl  =  """   expression interpolation        Dear  Mr  ${name},          You're  the  winner  of  the  lottery!          Yours  sincerly,          Dave   """   ! assert  tmpl.toString().contains('Groovy') @glaforge — @smaldini / #DV13-rtweb !59
  • 162. Surprising numbers... System.out.println(  2.0  -­‐  1.1  ); @glaforge — @smaldini / #DV13-rtweb !60
  • 163. Surprising numbers... System.out.println(  2.0  -­‐  1.1  ); 0.8999999999999999 @glaforge — @smaldini / #DV13-rtweb !60
  • 164. Surprising numbers... System.out.println(  2.0  -­‐  1.1  ); 0.8999999999999999 @glaforge — @smaldini / #DV13-rtweb !60
  • 165. Surprising numbers... System.out.println(  3  /  2  ); @glaforge — @smaldini / #DV13-rtweb !61
  • 166. Surprising numbers... System.out.println(  3  /  2  ); 1 @glaforge — @smaldini / #DV13-rtweb !61
  • 167. Surprising numbers... System.out.println(  3  /  2  ); 1 @glaforge — @smaldini / #DV13-rtweb !61
  • 168. BigDecimal by default! assert  2.0  -­‐  1.1  ==  0.9 assert  3  /  2  ==  1.5 @glaforge — @smaldini / #DV13-rtweb !62
  • 169. BigDecimal by default! assert  2.0  -­‐  1.1  ==  0.9 assert  3  /  2  ==  1.5 One of the reasons why microbenchmarks sometimes showed Groovy to be slow... @glaforge — @smaldini / #DV13-rtweb !62
  • 170. BigDecimal by default! assert  2.0  -­‐  1.1  ==  0.9 assert  3  /  2  ==  1.5 One of the reasons why microbenchmarks sometimes showed Groovy to be slow... @glaforge — @smaldini / #DV13-rtweb But you can use doubles & floats for performance, with ‘d’ or ‘f ’ suffixes or with explicit type !62
  • 171.
  • 172. Powerful switch / case on steroids
  • 173. Powerful switch / case on steroids switch(obj)  {          case  123:                  "number  123";              break          case  "abc":              "string  abc";              break          case  String:            "is  a  string";            break          case  [1,  2,  3]:      "in  list";                    break          case  ~/.*o+.*/:      "regex  match";            break          case  {  it  <  3  }:    "closure  criteria";  break          default:                    "unknown"   }
  • 174. Named arguments move  obj,  x:  3,  y:  4 @glaforge — @smaldini / #DV13-rtweb !64
  • 175. Named arguments move  obj,  x:  3,  y:  4 Normal argument @glaforge — @smaldini / #DV13-rtweb !64
  • 176. Named arguments move  obj,  x:  3,  y:  4 Normal argument @glaforge — @smaldini / #DV13-rtweb Named argument !64
  • 177. Named arguments move  obj,  x:  3,  y:  4 Normal argument Named argument Calls: move(Map m, Object) @glaforge — @smaldini / #DV13-rtweb !64
  • 178. Command chains • Ability to chain method calls without parentheses and dots move  forward  at  3.km/h @glaforge — @smaldini / #DV13-rtweb !65
  • 179. Command chains • Ability to chain method calls without parentheses and dots move  forward  at  3.km/h Actually equivalent to: move(forward).at(3.getKm().div(h)) @glaforge — @smaldini / #DV13-rtweb !65
  • 180. Named arguments & command chains check  that:  vodka  tastes  good @glaforge — @smaldini / #DV13-rtweb !66
  • 181. Named arguments & command chains check  that:  vodka  tastes  good Will call: check(that: vodka).tastes(good) @glaforge — @smaldini / #DV13-rtweb !66
  • 182. Multiple assignment and destructuring def  (a,  b)  =  ['A',  'B']   ! (a,  b)  =  [b,  a]   ! def  (int  i,  int  j)  =  [1,  2]   ! def  geocode(String  place)  {          return  [45.4,  2.3]   }   ! def  (la,  lo)  =  geocode("Paris")   ! assert  la  ==  45.4  &&  lo  ==  2.3 @glaforge — @smaldini / #DV13-rtweb !67
  • 183. Multiple assignment and destructuring def  (a,  b)  =  ['A',  'B']   ! (a,  b)  =  [b,  a]   Classic « swap » ! def  (int  i,  int  j)  =  [1,  2]   ! def  geocode(String  place)  {          return  [45.4,  2.3]   }   ! def  (la,  lo)  =  geocode("Paris")   ! assert  la  ==  45.4  &&  lo  ==  2.3 @glaforge — @smaldini / #DV13-rtweb !67
  • 184. Multiple assignment and destructuring def  (a,  b)  =  ['A',  'B']   ! With types (a,  b)  =  [b,  a]   Classic « swap » ! def  (int  i,  int  j)  =  [1,  2]   ! def  geocode(String  place)  {          return  [45.4,  2.3]   }   ! def  (la,  lo)  =  geocode("Paris")   ! assert  la  ==  45.4  &&  lo  ==  2.3 @glaforge — @smaldini / #DV13-rtweb !67
  • 185. Multiple assignment and destructuring def  (a,  b)  =  ['A',  'B']   ! With types (a,  b)  =  [b,  a]   Classic « swap » ! def  (int  i,  int  j)  =  [1,  2]   ! Method returning a list def  geocode(String  place)  {          return  [45.4,  2.3]   }   ! def  (la,  lo)  =  geocode("Paris")   ! assert  la  ==  45.4  &&  lo  ==  2.3 @glaforge — @smaldini / #DV13-rtweb !67
  • 186. Multiple assignment and destructuring def  (a,  b)  =  ['A',  'B']   ! With types (a,  b)  =  [b,  a]   Classic « swap » ! def  (int  i,  int  j)  =  [1,  2]   ! Method returning a list def  geocode(String  place)  {          return  [45.4,  2.3]   }   Destructuring ! def  (la,  lo)  =  geocode("Paris")   ! assert  la  ==  45.4  &&  lo  ==  2.3 @glaforge — @smaldini / #DV13-rtweb !67
  • 187. Multiple assignment and destructuring class  Point  {          double  x,  y   !        double  getAt(int  idx)  {                  if  (idx  ==  0)  x                  else  if  (idx  ==  1)  y                  else  throw  new  Exception("Wrong  index")          }   }   ! def  (x,  y)  =  new  Point(x:  48.3,  y:  3.5)   ! assert  x  ==  48.3  &&  y  ==  3.5 @glaforge — @smaldini / #DV13-rtweb !68
  • 188. Multiple assignment and destructuring class  Point  {          double  x,  y   Method signature convention: getAt(int) !        double  getAt(int  idx)  {                  if  (idx  ==  0)  x                  else  if  (idx  ==  1)  y                  else  throw  new  Exception("Wrong  index")          }   }   ! def  (x,  y)  =  new  Point(x:  48.3,  y:  3.5)   ! assert  x  ==  48.3  &&  y  ==  3.5 @glaforge — @smaldini / #DV13-rtweb !68
  • 189. Multiple assignment and destructuring class  Point  {          double  x,  y   Method signature convention: getAt(int) !        double  getAt(int  idx)  {                  if  (idx  ==  0)  x                  else  if  (idx  ==  1)  y                  else  throw  new  Exception("Wrong  index")          }   }   Transparent destructuring ! def  (x,  y)  =  new  Point(x:  48.3,  y:  3.5)   ! assert  x  ==  48.3  &&  y  ==  3.5 @glaforge — @smaldini / #DV13-rtweb !68
  • 190. Operator overloading import  static  Unit.*   ! enum  Unit  {      M(1),  KM(1000)   !    double  mult      Unit(double  mult)  {          this.mult  =  mult      }   } @glaforge — @smaldini / #DV13-rtweb !69
  • 191. Operator overloading import  static  Unit.*   ! enum  Unit  {      M(1),  KM(1000)   ! import  groovy.transform.Immutable   import  static  Unit.*      double  mult      Unit(double  mult)  {   !        this.mult  =  mult   @Immutable      }   class  Distance  {   }    double  q      Unit  u   !    Distance  plus(Distance  d)  {          new  Distance(    q  *      u.mult  +  
                                  d.q  *  d.u.mult,  M)      }   } @glaforge — @smaldini / #DV13-rtweb !69
  • 192. Operator overloading import  static  Unit.*   ! import  static  Unit.*   enum  Unit  {      M(1),  KM(1000)   ! def  d10  =  new  Distance(10,  M)   ! import  groovy.transform.Immutable   def  d15  =  new  Distance(15,  M)      double  mult   import  static  Unit.*   !    Unit(double  mult)  {   ! def  d25  =  d10  +  d15          this.mult  =  mult   @Immutable   !    }   class  Distance  {   assert  d25.q  ==  25  &&  d25.u  ==  M }    double  q      Unit  u   !    Distance  plus(Distance  d)  {          new  Distance(    q  *      u.mult  +  
                                  d.q  *  d.u.mult,  M)      }   } @glaforge — @smaldini / #DV13-rtweb !69
  • 193. Operator overloading import  static  Unit.*   ! import  static  Unit.*   enum  Unit  {      M(1),  KM(1000)   ! def  d10  =  new  Distance(10,  M)   ! import  groovy.transform.Immutable   def  d15  =  new  Distance(15,  M)      double  mult   import  static  Unit.*   !    Unit(double  mult)  {   ! def  d25  =  d10  +  d15          this.mult  =  mult   @Immutable   !    }   class  Distance  {   assert  d25.q  ==  25  &&  d25.u  ==  M }    double  q      Unit  u   Overload the ‘+’ operator @glaforge — @smaldini / #DV13-rtweb !    Distance  plus(Distance  d)  {          new  Distance(    q  *      u.mult  +  
                                  d.q  *  d.u.mult,  M)      }   } !69
  • 194. Operator overloading import  static  Unit.*   ! import  static  Unit.*   enum  Unit  {      M(1),  KM(1000)   ! def  d10  =  new  Distance(10,  M)   ! import  groovy.transform.Immutable   def  d15  =  new  Distance(15,  M)      double  mult   import  static  Unit.*   !    Unit(double  mult)  {   ! def  d25  =  d10  +  d15          this.mult  =  mult   @Immutable   !    }   class  Distance  {   assert  d25.q  ==  25  &&  d25.u  ==  M }    double  q      Unit  u   Overload the ‘+’ operator @glaforge — @smaldini / #DV13-rtweb !    Distance  plus(Distance  d)  {          new  Distance(    q  *      u.mult  +  
                                  d.q  *  d.u.mult,  M)      }   } Use ‘+’ !69
  • 195. Operator overloading a  +  b      //  a.plus(b)   a  -­‐  b      //  a.minus(b)   a  *  b      //  a.multiply(b)   a  /  b      //  a.div(b)   a  %  b      //  a.modulo(b)   a  **  b    //  a.power(b)   a  |  b      //  a.or(b)   a  &  b      //  a.and(b)   a  ^  b      //  a.xor(b)   a[b]        //  a.getAt(b)   a  <<  b    //  a.leftShift(b)   a  >>  b    //  a.rightShift(b)   a  >>>  b  //  a.rightShiftUnsigned(b)   +a            //  a.unaryPlus()   -­‐a            //  a.unaryMinus()   ~a            //  a.bitwiseNegate() @glaforge — @smaldini / #DV13-rtweb !70
  • 196. Operator overloading a  +  b      //  a.plus(b)   a  -­‐  b      //  a.minus(b)   a  *  b      //  a.multiply(b)   Operator overloading is a  /  b      //  a.div(b)   a  %  b      //  a.modulo(b)   just a convention on a  **  b    //  a.power(b)   method names a  |  b      //  a.or(b)   a  &  b      //  a.and(b)   a  ^  b      //  a.xor(b)   a[b]        //  a.getAt(b)   a  <<  b    //  a.leftShift(b)   a  >>  b    //  a.rightShift(b)   a  >>>  b  //  a.rightShiftUnsigned(b)   +a            //  a.unaryPlus()   -­‐a            //  a.unaryMinus()   ~a            //  a.bitwiseNegate() @glaforge — @smaldini / #DV13-rtweb !70
  • 197. Power asserts def  (a,  b,  c)  =  [20,  30,  40]   ! assert  a  *  (b  -­‐  1)  /  10  ==  3  *  c  /  2  +  1 @glaforge — @smaldini / #DV13-rtweb !71
  • 198. Power asserts def  (a,  b,  c)  =  [20,  30,  40]   ! assert  a  *  (b  -­‐  1)  /  10  ==  3  *  c  /  2  +  1 Assertion  failed:     ! assert  a  *  (b  -­‐  1)  /  10  ==  3  *  c  /  2  +  1                |  |    |  |        |        |        |  |  |      |                |  580|  29      58      false|  |  60    61                20      30                              |  40                                                            120   !   at  script1.run(script1.groovy:3) @glaforge — @smaldini / #DV13-rtweb !71
  • 199. Power asserts def  (a,  b,  c)  =  [20,  30,  40]   ! assert  a  *  (b  -­‐  1)  /  10  ==  3  *  c  /  2  +  1 Assertion  failed:     ! assert  a  *  (b  -­‐  1)  /  10  ==  3  *  c  /  2  +  1                |  |    |  |        |        |        |  |  |      |                |  580|  29      58      false|  |  60    61                20      30                              |  40                                                            120   ! Invented by the Spock testing framework   at  script1.run(script1.groovy:3) @glaforge — @smaldini / #DV13-rtweb !71
  • 200. Null handling class  Order  {          LineItem  line   }   class  LineItem  {          int  quantity          Item  item   }   class  Item  {          String  name   }   ! def  o  =  new  Order(          line:  new  LineItem(                  quantity:  2,                  item:  null))   ! println  o.line.item.name @glaforge — @smaldini / #DV13-rtweb !72
  • 201. Null handling class  Order  {          LineItem  line   }   class  LineItem  {          int  quantity          Item  item   }   class  Item  {          String  name   }   ! def  o  =  new  Order(          line:  new  LineItem(                  quantity:  2,                  item:  null))   With Java, you only get an NPE. No idea where it came from! ! println  o.line.item.name @glaforge — @smaldini / #DV13-rtweb !72
  • 202. Null handling class  Order  {          LineItem  line   }   class  LineItem  {          int  quantity          Item  item   }   class  Item  {          String  name   }   ! def  o  =  new  Order(          line:  new  LineItem(                  quantity:  2,                  item:  null))   ! println  o.line.item.name @glaforge — @smaldini / #DV13-rtweb With Java, you only get an NPE. No idea where it came from! Groovy will say: Cannot get property ‘name’ on null object !72
  • 203. Null handling class  Order  {          LineItem  line   }   class  LineItem  {          int  quantity          Item  item   }   class  Item  {          String  name   }   ! def  o  =  new  Order(          line:  new  LineItem(                  quantity:  2,                  item:  null))   ! println  o.line.item.name @glaforge — @smaldini / #DV13-rtweb !72
  • 204. Null handling class  Order  {          LineItem  line   }   class  LineItem  {          int  quantity          Item  item   }   class  Item  {          String  name   }   o?.line?.item?.name ! def  o  =  new  Order(          line:  new  LineItem(                  quantity:  2,                  item:  null))   ! println  o.line.item.name @glaforge — @smaldini / #DV13-rtweb !72
  • 205. Null handling class  Order  {          LineItem  line   }   class  LineItem  {          int  quantity          Item  item   }   class  Item  {          String  name   }   o?.line?.item?.name Safe navigation: will just return null; No NPE ! def  o  =  new  Order(          line:  new  LineItem(                  quantity:  2,                  item:  null))   ! println  o.line.item.name @glaforge — @smaldini / #DV13-rtweb !72
  • 206.
  • 208. The Truth, the Groovy Truth! And what if I could customize the truth?
  • 209. The Groovy Truth assert  !(  null  )   assert  !(    ""    )   assert  !(    []    )   assert  !(      0    ) assert  new  Object()   assert  "string"   assert  [1,  2,  3]   assert  1234 @glaforge — @smaldini / #DV13-rtweb !74
  • 210. The Groovy Truth null, empty, 0-sized, zero are coerced to false assert  !(  null  )   assert  !(    ""    )   assert  !(    []    )   assert  !(      0    ) assert  new  Object()   assert  "string"   assert  [1,  2,  3]   assert  1234 @glaforge — @smaldini / #DV13-rtweb !74
  • 211. The Groovy Truth null, empty, 0-sized, zero are coerced to false assert  !(  null  )   assert  !(    ""    )   assert  !(    []    )   assert  !(      0    ) assert  new  Object()   assert  "string"   assert  [1,  2,  3]   assert  1234 @glaforge — @smaldini / #DV13-rtweb true otherwise !74
  • 212. Customizing the truth! class  Account  {          String  name          boolean  disabled  =  false   !        boolean  asBoolean()  {  !disabled  }   }   ! assert    new  Account(name:  'current')   assert  !new  Account(name:  'old',  disabled:  true) @glaforge — @smaldini / #DV13-rtweb !75
  • 213. Customizing the truth! class  Account  {          String  name          boolean  disabled  =  false   !        boolean  asBoolean()  {  !disabled  }   }   ! assert    new  Account(name:  'current')   assert  !new  Account(name:  'old',  disabled:  true) while (account), if (account), etc… @glaforge — @smaldini / #DV13-rtweb !75
  • 214. ?:
  • 216. Towards Elvis... @glaforge — @smaldini / #DV13-rtweb !77
  • 217. Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] @glaforge — @smaldini / #DV13-rtweb !77
  • 218. Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] @glaforge — @smaldini / #DV13-rtweb !77
  • 219. Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] if  (x  !=  null  &&  x.size()  >  0)  x  else  y @glaforge — @smaldini / #DV13-rtweb !77
  • 220. Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] if  (x  !=  null  &&  x.size()  >  0)  x  else  y if  (x  &&  x.size())  x  else  y @glaforge — @smaldini / #DV13-rtweb !77
  • 221. Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] if  (x  !=  null  &&  x.size()  >  0)  x  else  y if  (x  &&  x.size())  x  else  y if  (x)  x  else  y @glaforge — @smaldini / #DV13-rtweb !77
  • 222. Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] if  (x  !=  null  &&  x.size()  >  0)  x  else  y if  (x  &&  x.size())  x  else  y if  (x)  x  else  y x  ?  x  :  y @glaforge — @smaldini / #DV13-rtweb !77
  • 223. Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] if  (x  !=  null  &&  x.size()  >  0)  x  else  y if  (x  &&  x.size())  x  else  y if  (x)  x  else  y x  ?  x  :  y x  ?:  y @glaforge — @smaldini / #DV13-rtweb !77
  • 224. Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] if  (x  !=  null  &&  x.size()  >  0)  x  else  y if  (x  &&  x.size())  x  else  y if  (x)  x  else  y x  ?  x  :  y x  ?:  y Null, empty, zerosized... false, otherwise true! @glaforge — @smaldini / #DV13-rtweb !77
  • 225. Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] if  (x  !=  null  &&  x.size()  >  0)  x  else  y if  (x  &&  x.size())  x  else  y if  (x)  x  else  y x  ?  x  :  y x  ?:  y Good old ternary operator @glaforge — @smaldini / #DV13-rtweb Null, empty, zerosized... false, otherwise true! !77
  • 226. Towards Elvis... def  (x,  y)  =  ['MacBook  Pro',  'unknown'] if  (x  !=  null  &&  x.size()  >  0)  x  else  y if  (x  &&  x.size())  x  else  y if  (x)  x  else  y x  ?  x  :  y x  ?:  y Elvis! @glaforge — @smaldini / #DV13-rtweb Good old ternary operator Null, empty, zerosized... false, otherwise true! !77
  • 227. AST transformations • Abstract Syntax Tree – in memory representation of your program
 before being compiled into bytecode ! • AST transformation == process of transforming the AST of a program before it’s compiled ! • Macro-like compiler hook! @glaforge — @smaldini / #DV13-rtweb !78
  • 228. Lots of AST transformations... • Code generation – @ToString, @EqualsAndHashCode, @Canonical, @TupleConstructor, @InheritConstructors, @Category, @IndexedProperty, @Lazy, @Newify • Class design – @Delegate, @Immutable, @Memoized, 
 @Singleton, @Mixin • Logging – @Log, @Log4j, @Log4j2, @Slf4j @glaforge — @smaldini / #DV13-rtweb !79
  • 229. Lots of AST transformations... • Safer scripting – @ConditionalInterrupt, @ThreadInterrupt, @TimedInterupt • Compiler directives – @Field, @PackageScope, @AnnotationCollector, @DelegatesTo, @TypeChecked, @CompileStatic, @CompileDynamic • Swing patterns – @Bindable, @ListenerList, @Vetoable @glaforge — @smaldini / #DV13-rtweb !80
  • 230. Lots of AST transformations... • Dependencies handling – @Grab, @GrabConfig, @GrabExclude, @GrabResolver • Test assistance – @NotYetImplemented, @ASTTest @glaforge — @smaldini / #DV13-rtweb !81
  • 231. Immutability • Implement immutability 
 by the book ! – final class – tuple-style constructor – private final backing fields – defensive copying of collections – equals() and hashCode() methods – toString() method – ... @glaforge — @smaldini / #DV13-rtweb !82
  • 232. Immutability • Implement immutability 
 by the book ! Can be error-prone to write immutable classes oneself! – final class – tuple-style constructor – private final backing fields – defensive copying of collections – equals() and hashCode() methods – toString() method – ... @glaforge — @smaldini / #DV13-rtweb !82
  • 233. Immutability • A Person class with – a String name – an int age public final class Person {! private final String name;! private final int age;! ! ! ! ! ! ! public Person(String name, int age) {! this.name = name;! this.age = age;! }! public String getName() {! return name;! }! public int getAge() {! return age;! }! public int hashCode() {! return age + 31 * name.hashCode();! }! public boolean equals(Object other) {! if (other == null) {! return false;! }! if (this == other) {! return true;! }! if (Person.class != other.getClass()) {! return false;! }! Person otherPerson = (Person)other;! if (!name.equals(otherPerson.getName()) {! return false;! }! if (age != otherPerson.getAge()) {! return false;! }! return true;! }! public String toString() {! return "Person(" + name + ", " + age + ")";! }! }! @glaforge — @smaldini / #DV13-rtweb !83
  • 234. Immutability • A Person class with – a String name – an int age public final class Person {! private final String name;! private final int age;! ! ! ! ! ! ! public Person(String name, int age) {! this.name = name;! this.age = age;! }! Damn verbose Java! public String getName() {! return name;! }! public int getAge() {! return age;! }! public int hashCode() {! return age + 31 * name.hashCode();! }! public boolean equals(Object other) {! if (other == null) {! return false;! }! if (this == other) {! return true;! }! if (Person.class != other.getClass()) {! return false;! }! Person otherPerson = (Person)other;! if (!name.equals(otherPerson.getName()) {! return false;! }! if (age != otherPerson.getAge()) {! return false;! }! return true;! }! public String toString() {! return "Person(" + name + ", " + age + ")";! }! }! @glaforge — @smaldini / #DV13-rtweb !83
  • 235. Immutability • A Person class with – a String name – an int age public final class Person {! private final String name;! private final int age;! ! ! ! ! ! ! public Person(String name, int age) {! this.name = name;! this.age = age;! }! Damn verbose Java! public String getName() {! return name;! }! public int getAge() {! return age;! }! public int hashCode() {! return age + 31 * name.hashCode();! }! public boolean equals(Object other) {! if (other == null) {! return false;! }! if (this == other) {! return true;! }! if (Person.class != other.getClass()) {! return false;! }! Person otherPerson = (Person)other;! if (!name.equals(otherPerson.getName()) {! return false;! }! if (age != otherPerson.getAge()) {! return false;! }! return true;! }! Although it’s also a valid Groovy program! public String toString() {! return "Person(" + name + ", " + age + ")";! }! }! @glaforge — @smaldini / #DV13-rtweb !83
  • 236. @Immutable import  groovy.transform.*   ! @Immutable   class  Person  {          String  name          int  age   } @glaforge — @smaldini / #DV13-rtweb !84
  • 237. Memoization • Cache the result of previous invocations of closures or methods with the same set of argument values import  groovy.transform.*   ! @Memoized   long  fib(long  n)  {          if  (n  ==  0)  0          else  if  (n  ==  1)  1          else  fib(n  -­‐  1)  +  fib(n  -­‐  2)   }   ! println  fib(40) @glaforge — @smaldini / #DV13-rtweb !85
  • 238. Memoization • Cache the result of previous invocations of closures or methods with the same set of argument values import  groovy.transform.*   Best applied to side-effect free functions ! @Memoized   long  fib(long  n)  {          if  (n  ==  0)  0          else  if  (n  ==  1)  1          else  fib(n  -­‐  1)  +  fib(n  -­‐  2)   }   ! println  fib(40) @glaforge — @smaldini / #DV13-rtweb !85
  • 239.
  • 241. Groovy allows you to be lazy The compiler will do the job for you
  • 242. Groovy allows you to be lazy More concise, more readable code The compiler will do the job for you
  • 243. Groovy allows you to be lazy More concise, more readable code The compiler will do the job for you Less stuff to maintain and worry about
  • 244. @TypeChecked & @CompileStatic • Static type checking with @TypeChecked, throws compilation errors on... – typos in method and variable names – incompatible return types – wrong type assignments ! • Supports fine-grained type inference – « Least Upper Bound » – « Flow typing » @glaforge — @smaldini / #DV13-rtweb !87
  • 245. @TypeChecked & @CompileStatic • Static type checking with @TypeChecked, throws compilation errors on... – typos in method and variable names – incompatible return types – wrong type assignments ! You can even extend the static type checker! • Supports fine-grained type inference – « Least Upper Bound » – « Flow typing » @glaforge — @smaldini / #DV13-rtweb !87
  • 246. @TypeChecked & @CompileStatic • Static type checking with @TypeChecked, throws compilation errors on... – typos in method and variable names – incompatible return types – wrong type assignments ! You can even extend the static type checker! • Supports fine-grained type inference – « Least Upper Bound » – « Flow typing » @glaforge — @smaldini / #DV13-rtweb Type check DSLs or dynamic features! !87