Scala is a programming language that combines object-oriented and functional programming. It runs on the Java Virtual Machine and is designed to grow with user demands through libraries. Play 2.0 is a web application framework written in Scala that allows for rapid development through its Model-View-Controller architecture and local development server. Cloud Foundry is an open Platform as a Service that allows developers to easily deploy and scale applications, including those written in Scala and Play 2.0.

1. “Scala,
Play 2.0 &
Cloud Foundry”
By:
Pray Desai
Intern – Scala Developer Advocate
Cloud Foundry
@praydesai

2. Scala

3. Introduction
• Scala is a programming language that combines
features of object-oriented programming with
functional programming.
• Scala (skah-la) stands for Scalable language
• Designed to grow with the demands of users
• Growing new types by defining easy-to-use
libraries
• Growing new control constructs such as
concurrent programming
• Write small scripts as well as build large systems

4. • Scala runs on the Java platform (Java Virtual
Machine) as well as Dot Net platform.
• Designed by Martin Odersky in 2001 at EPFL, who
was also one of the creators of javac compiler
and generic java
• Open source
• Released in 2004
• Second version v 2.0 in 2006
• Current version is 2.9.2

5. Q : What is the one thing that makes
Scala scalable ?
Ans.: Combining OO with FP

6. Object Oriented programming
• Purely OO
• Every value is an object
• Every operation is a method
• No primitive types, everything is object
• 1 + 2 invokes a method + defined in class Int

7. Functional programming
• Not purely FP

8. What is Functional programming ?
• Concept came from Lambda Calculus
• Computation by evaluation of functions
• Basic fundamental is to evaluate an expression and use its
result for some other expression
• Made up of functions that always return some value
• Char of FP absent in IP & OO : Always return same value for
same inputs ; map input values to output values
• No side effects : state does not change
• Immutable data : Cannot change the value once set;
so no need to lock the access of shared data
• Reuse same code in diff parts of the programs
• Free order of code execution

9. Functional programming in Scala
• Partially FP
• Supports mutable data as well as immutable
• Variables as well as Values
• Functions are first-class values just like an integer or string
• Higher – order functions: allows to combine parts of code easily
• Pass functions as arguments to other functions
• Return functions as results from functions
• Store functions in variables
• Define a function inside another function
• Closures - functions that capture variables defined in scope. Function can
access variable even after scope is exited.
• Modern Collection Library that allows parallel execution of functions
• Supports immutable data structures in its libraries so no need of locks to
access.

10. Syntax
The implementation is similar to Java or C. We use the same operators and
control structures.
• Function definition starts with “def”
def fact(x:Int) : Int = if(x==0)1 else x*fact(x-1)
• variable definitions start with “var” and definitions of values (i.e. read only
variables) start with “val”.
• val is immutable where var is mutable
Error : Correct:
val x=123 var x=123
x=x+1 x=x+1
• No need to write public. It is default visibility.
• No semicolon
• No need to specify data type, compiler infers it from context
• Array types are written as Array[Int] rather than Int[], and array
selections are written a(i) rather than a[i].
• Looping becomes easy with the use of functional literals
for (i<-0 to 10) print(i)
for (I <-0 until 10) print(i)

11. Comparison with Java
• It is compatible with existing Java programs and we can
use all java libraries.
• Its operates similar to Java. Its compiler generates byte
code that is similar to java bytecode
• JVM cannot differentiate between scala code and java
code. The only difference is an extra runtime library.
• Scala code can be decompiled to readable Java code,
with the exception of certain constructor operations.
• Runs on Eclipse and Netbeans IDE just as Java.
• The only two things in scala which are absent in java
are richer type system and support for functional
programming.

12. Traits
• Traits are like interfaces in java but can also have
method implementations and fields which can
then be reused by mixing them into classes.
• Unlike class inheritance, in which each class must
inherit from just one superclass, a class can mix in
any number of traits.
• Members of class are added to members of
multiple traits
• Avoids diamond problem in multiple inheritance
• Automatically add methods to a class in terms of
methods the class already has.
• Make a thin interface into a rich one.

13. Abstract Class
• Class abstractions are extended by subclassing
abstract class class1 extends trait1 {
case subclass1 extends class1
case subclass2 extends class1
}

14. No getters and setters
public class Person{
private String firstName = null; public class Person {
private String lastName = null; var firstName = ""
private int age = 0; var lastName = ""
var age = 0
public void setFirstName(String }
firstName) {
this.firstName = firstName;
}
public String getFirstName() {
return firstName;
}
public void setLastName(String
lastName) {
this.lastName = lastName;
}
http://hedleyproctor.com/2012/04/why-java-
public String getLastName() { developers-should-be-learning-scala/
return lastName;

15. Data Structures
[Containers of values]
1. List
• Collection of data that can be randomly accessed
and can have different datatypes
• Immutable, new list generated every time
• Int list : val a =List(1,2,3)
• Combination : val b =List(“a”,’’b”,4)
• Concate lists : a ::: b
• Any is catchall datatype
• Access value: b(2)

16. 2. Set
• Similar to list but independent of order
• Cannot combine datatypes in single set
• Immutable, new set generated everytime
• Set(1,2,3) == Set(3,1,2) true
• List(1,2,3)==List(3,1,2) false
var a = Set(1,2,3)
val b = Set(0,1,5)
• Add/remove value from set :
a=a+4
a=a-3
• Union : a ++ b
• Intersection : a ** b

17. 3. Map
• Key-value pair which maps keys of type A to
values of type B
val m = Map (0 -> “abc”, 1->”def”, 2->”xyz”)
m(2)

18. 4. Tuple
• Store different data types in same variable
• Used to return multiple objects from method
• Storing/Retrieving rows of tables in database
val address=(201,”s 4 th st”)
address (._1)
address (._2)
address

19. Pattern Matching
• Conditionally execute code based on some data
provided
• Used in parsing xml and parsing messages
between threads
• Similar to switch case, no breaks
• def chek(a:Int) { a match
case 0 => …
case 1 => ..
case _ => ..
}

20. Support to Parallel Processing
• In v2.9, collections support parallel operations
• It has two methods :
c.par which returns parallel version of c
c.seq which returns sequential version of c
• Divide work by number of processors
• Threads maintain work queues

21. Actors
• Actors are basic units of concurrency implemented
on top of threads.
• Two basic operations: message send and receive.
• A send is asynchronous without waiting for the
message to be received and processed
• Every actor has a mailbox in which incoming
messages are queued.
• A receive block consists of a number of cases that
each query the mailbox with a message pattern.
• The first message in the mailbox that matches any
of the cases is selected, and the corresponding
action is performed on it.

22. Scala features in Java 8
• Lambda expressions
• Higher order functions
• Parallel Collections
• Function chaining
• Traits
www.infoq.com/articles/java-8-vs-scala

23. Lambda expressions
Function Literal
• Function with input parameters and function
body
• (type parameter) -> function_body
• ex: (String s1, String s2) - > s1.length()-
s2.length();

24. Why Scala ?
• Compatible - with JVM
• Concise - reduced code
//java //scala
class student { class student(id:Int, name:String)
private int id;
private String name;
public student (int id, String name) {
this.id = id;
this.name = name;
}
}
• High-level - more simpler, shorter code and easy to understand,
Use and design libraries for clear and concise code
• Statically typed – variable type known at compile time, less runtime errors
• XML literals - create and consuming XML quite easy within your applications.
• Parallel Processing - .par, .seq, Actors

25. Testing
There are several ways to test code in Scala :
• ScalaTest
Supports multiple testing styles and can integrate with Java-based
testing frameworks
• ScalaCheck
Generates automatic test case and minimizes failing test cases
• Specs2
Library for writing executable software specifications
• ScalaMock
Provides support for testing high-order and curried functions
• JUnit , TestNG
Unit testing frameworks for java
• Borachio
Provides support for testing high-order and curried functions.

26. Companies that work on Scala
• Twitter - for queuing system that handles heavy load
• LinkedIn – used in their framework “Nobert”
• Sony -library that manages updates, rollbacks and changes
to database schemas
• Siemens – application for company wide employees
communication to boost productivity
• Xerox – to improve customer experience
• Grid Grain - provides DSL for cloud computing
• Swiss bank UBS - for general production usage
• FourSquare - for message passing
• The Guardian newspaper - content API for selecting and
collecting news content
• Juniper Networks – distributed software based on Akka
middleware for multi-core processors

27. Limitations
• Syntax
Difficult to understand as reading backwards.
The return value is at the end of the
declaration, and the types are declared after
the variable names.
• Slow compilation and interpreter
Takes much time to compile and run. We can
use fsc compiler now (Fast Scala Compiler),
which essentially stays resident in memory.

28. Further Enhancements
• Developer tools- Akka/Scala stack, Akka
framework, which is the most widely used
parallel computation framework on top of Java
• Style-checking tool, to be integrated in next
release of the IDE.
• Visual Studio integration.
• Scala for JavaScript
• V2.10 : better support for dynamic languages,
better reflection, better support for parallelism.

29. Conclusion
• “If I were to pick a language to use on JVM other
than Java then it would be Scala” – James Gosling
• “Scala will be long term replacement of java, If
someone had told me about Scala then I would
have never created Groovy” – James Strachan ,
Creator of Groovy
• “Scala is current heir apparent to Java throne, no
other language capable to replace java than
scala” – Charlies Nutter, JRuby Lead

30. Scala Resources
• Programming in Scala, 2nd edition
by Martin Odersky
• http://www.scala-lang.org/
• http://twitter.github.com/scala_school/
• Free Online Course from 9/18/2012 for 7 weeks:
https://www.coursera.org/course/progfun

31. Installing Scala in Eclipse
• Current versions: IDE: 2.0.2 Scala: 2.9.x
• Required: JDK 5 or 6, Eclipse Helios or Indigo
• http://scala-ide.org/
• Copy the url for the current version
• Help -> Install New Software
OR
• Search Scala IDE in
Help -> Eclipse Market Place

32. Hello World Program
object Hello {
def main (args: Array[String])
{
println("Hello World")
}
}

33. Play 2.0

34. Play 2.0
• Web application framework
• MVC
• Light-weight
• Core written in Scala
• Local Host Server
• No need to add any external jars !
• Display errors in browser

35. Installing Play 2.0
• Required: JDK 6
• Download from
http://www.playframework.org/
• Unzip and add play directory to working path
• For Mac :
export PATH=$PATH:/Applications/play-2.0
• For Windows:
Set path in the global environment variable

36. Play commands
• Check Play is installed
play help
• Create a new Play app
play new <app-name>
cd <app-name>
• Run the app
play run
Go to browser and type - localhost:9000
Ctrl + D to stop server
• Clean the server
play clean

37. Play in Eclipse
• play eclipsify
• File -> Import -> Existing Projects into WS

38. Working Directory
• app
 controllers
 view
 model
• test
• conf
 application.conf
 routes
• logs
• project
• public
 images
 javascripts
 stylesheets

39. Hello World App
controllers/Application.scala views/index.scala.html
package controllers @(message: String)
import play.api._
import play.api.mvc._ @main("Welcome") {
@message
object Application extends Controller { }
def index = Action {
Ok(views.html.index("Hello World"))
}
}

40. Configure routes
conf/routes
# Home page
GET / controllers.Application.index
# Map static resources from the /public folder to /assets URL path
GET /assets/*file controllers.Assets.at(path="/public", file)

41. Play 2.0 Resources
• Go to the directory where you installed Play
play-2.0/documentation/Play 2.0 Doc.pdf
• Sample apps :
play-2.0/samples/scala
• http://www.playframework.org/documentatio
n/2.0.2/ScalaHome

42. Cloud Foundry

43. What is Cloud Foundry ?
• Open PaaS
• “Linux of the Cloud”
• Deploy and scale apps easily
• Focus just on coding
• Supports Scala & Play 2.0
• Choice of many other services and frameworks

44. Register
• http://cloudfoundry.com/signup
• Get your credentails in email
Welcome email
28
• Check your login on http://uaa.cloudfoundry.com

45. Install RVM and Ruby
For Mac:
• Install Ruby Version Manager https://rvm.io//
• rvm install 1.9.2
• rvm use 1.9.2

46. For Windows:
• http://rubyinstaller.org/downloads
Download version 1.9.2
• Check version by
ruby –v

47. Install vmc [command line tool]
• gem install vmc
• Check version (0.3.18 or higher)
vmc –v
• vmc login
• vmc target api.cloudfoundry.com

48. Deploy Play App on Cloud Foundry
• Package app
cd app1
play clean dist
Your application is ready in
/Users/desaip/app1/dist/app1-1.0-SNAPSHOT.zip
• vmc push --path=dist/app1-1.0-SNAPSHOT.zip

49. vmc push
[to deploy app for the first time]
desaip-mbp:~ desaip$ cd check1
desaip-mbp:check1 desaip$ vmc push --path=dist/check1-1.0-SNAPSHOT.zip
Application Name: check1
Detected a Play Framework Application, is this correct? [Yn]:
Application Deployed URL [check1.cloudfoundry.com]:
Memory reservation (128M, 256M, 512M, 1G, 2G) [256M]:
How many instances? [1]:
Create services to bind to 'check1'? [yN]: N
Would you like to save this configuration? [yN]: N
Creating Application: OK
Uploading Application:
Checking for available resources: OK
Processing resources: OK
Packing application: OK
Uploading (80K): OK
Push Status: OK
Staging Application 'check1': OK
Starting Application 'check1': OK
desaip-mbp:check1 desaip$

50. vmc update
[ to deploy updated app]
• cd app1
• play clean dist
• vmc update app1 --path=dist/app1-1.0-SNAPSHOT.zip
desaip-mbp:check1 desaip$ vmc update check1 --path=dist/check1-1.0-SNAPSHOT.zip
Uploading Application:
Checking for available resources: OK
Processing resources: OK
Packing application: OK
Uploading (80K): OK
Push Status: OK
Stopping Application 'check1': OK
Staging Application 'check1': OK
Starting Application 'check1': OK
desaip-mbp:check1 desaip$

51. vmc instances
[ to scale your app]
• To create another instance
vmc instances <app-name> +1
• To see other commands
vmc help

52. Cloud Foundry Resources
• http://blog.cloudfoundry.com/2012/05/31/clo
ud-foundry-now-supports-play/
• http://www.slideshare.net/chris.e.richardson/
cloud-foundry-bootcamp-at-contributingcode
• http://cloudstory.in/2012/07/tutorial-getting-
started-with-cloud-foundry-part-13/

53. THANK YOU