Play! Framework for JavaEE Developers

1. JavaTWO專業技術大會

2. Play!Framework for JavaEE Developers

3. Who am I Exp : JSP/Servlet , Tapestry , Spring/Hibernate/JavaEE , Wicket , Android , Grails , Play! Framework http://gplus.to/smallufo http://twitter.com/smallufo smallufo@gmail.com

4. Web Framework Experiences <ul><li>JSP/Servlet

5. Too old , cumbersome

6. Tapestry (old experience, T5 is very good)

7. Complicated , evolution/deprecation too fast

8. Wicket

9. Too elaborate , fail to see the wood for the trees

10. May lead to over-engineered architecture for OO-purism

11. Spend too much time refactoring

12. Maybe web component reuse is just a myth

13. Grails (old experience, without Groovy++)

14. Slow

15. Too many inconsistent DSLs (URL-mapping , DB , logging...)

16. Not Java , IDE unfriendly</li></li></ul><li>Conventional JavaEE Stack

17. Conventional JavaEE Stack <ul><li>Want standard page ?

18. Let's define JSP/JSTL (JSR-53)

19. And let Apache (or others) to implement Jakata Taglibs

20. Want web components ?

21. Let's define Java Server Faces (JSR-127)

22. And let communities to implement MyFaces, PrimeFaces, ICEfaces...

23. Want restful ?

24. Let's define JAX-RS (JSR-311)

25. And let communities to implement CXF, Jersey, RESTEasy, Wink...</li></li></ul><li>Conventional JavaEE Stack <ul><li>Lots of ...

26. Specs

27. Implementations

28. Configurations

29. Tedious , Error-prone

30. Unless you use a full-fledged JavaEE Server (Glassfish or WebLogic ...)

31. Layered

32. Defined by Standards/Specs

33. Assembled by Interfaces</li></ul>OVER ARCHITECTED

35. Play’s App Looks Like ? conf/routes app/App.java GET /hello App.hello public class App extends Controller { public static void hello() { User user = User.findById(1L); render(user); } } views/App/hello.html Hello World : ${user.name} http://localhost:9000/hello

36. And Play is ... <ul><li>A full stack framework (platform)

37. Totally independent of JavaEE environment

38. RESTful

39. No session

40. Stateless

41. Pure server side

42. Similar to Rails / Django

43. Rich domain model

44. Unlike JavaEE's anemic domain model</li></li></ul><li>Full Stack Framework? <ul><li>Bundles compiler , embedded server , hibernate , logger , test runner , email , groovy template engine, scala...

45. Can be packaged as a WAR and deployed to servlet containers</li></li></ul><li>Play! A Glued Pure Web Framework Shallow! Most libs are directly exposed to Play! & replaceable Where Magic Happens

46. Play! URLs are RESTful & SEO-friendly UGLY GRACEFUL <ul><li>/car/1

47. /listcar/page1/count10

48. /listcar/page1?count=10

49. /listcar/page/1/count/10

50. /car.jsp?id=1

51. /listcars.jsp?page=1&count=10

52. http://www.facebook.com/ photo.php? fbid=2121715487568& set=o.172881386106136& type=1&theater</li></li></ul><li>Play is not based on Servlet Many java server side frameworks (Spring MVC / Struts / Wicket / JSF / Tapestry ...) are based on servlets, but Play! is not! You cannot do such things : <ul><li>session.setAttribute("user" , user);

53. Use HttpSessionListener to count sessions (online users)

54. ServletFilter

55. Servlet-related securities

56. @ServletSecurity

57. <auth-constraint /> , <security-role /></li></li></ul><li>Play! is Stateless <ul><li>Play! shares nothing between each request!

58. The most important feature you have to keep in mind

59. No session!

60. Session is the source of all problems of the JavaEE platform!

61. Session replication

62. Sticky session

63. Play uses (delegates to) memcached to eliminates such headaches</li></li></ul><li>Play's Informative Error Page

64. Play's Domain Objects Are Rich Play *Spring promoted JavaEE User extends Model User extends Object UserDao.java <ul><li>save(User u)</li></ul>User u = new User(...) u.save() UserDaoImpl implements UserDao <ul><li>void setEntityManager(...)

65. save(User u)</li></ul>Client.java @Inject UserDao userDao User u = new User(...) userDao.save(u) VS *JPA advocates eliminating the DAO layer

66. Play's Architecture $ play new myproj myproj app controllers models conf application.conf views messages lib foo routes modules bar public images javascripts src stylesheets

67. conf/application.conf application.name=myapp application.mode=dev application.secret=OOXXOOXXOOXXOOXXOOXX http.port=9000 java.source=1.6 db.url=jdbc:mysql:... db.driver=com.mysql.jdbc.Driver db.user=user db.pass=pass hibernate.use_sql_comments=true hibernate.format_sql = true XForwardedSupport=127.0.0.1

68. Play's Architecture controllers app MyController.java public static void index() public static void show() models views MyController index.html foo show.html bar

69. conf/routes HTTP method URI Pattern Action GET / App.index POST /login App.login GET /tag/{name} App.tag(name) GET /list/{page} App.list(page) GET /list/{<[0-9]+>page} App.list(page) GET /list/{page}/{count} App.list(page,count) GET /public/ staticDir:public * /{controller}/{action} {controller}.{action}

70. Play's Request Life Cycle

71. Controllers and Redirections public class App extends play.mvc.Controller { public static void index() { render(); // views/App/index.html contains a login form } public static void login(String name,String passwd) { if(...) // success welcome(); else // failed index(); } public static void welcome() { render(); // renders views/App/welcome.html } }

72. Controller Interceptions public class App extends play.mvc.Controller { @play.mvc.Before(unless={“index”, “login”}) public static void intercept() { if (session.get("uid")==null) index(); } public static void index() {...} public static void login(String name,Stringpasswd){..} public static void welcome() {...} }

73. Session : A Signed Cookie public static void login(String name , String passwd) { User u = ... if (...) { session.put("uid" , u.id); } } Only put index data to session Never store sensitive data signed, uneditable!

74. Controller Revisited public static void show(Long uid, String type) { User u = ... if (type.equals("json") { renderJSON(u); // provided by GSON } else if (type.equals("xml") { renderXml(u); // provided by XStream } render(u); } Why not continue rendering? play.mvc.Controller throw new RenderJson(jsonString); throw new RenderXml(xml); throw new RenderTemplate(...);

75. Controller and View controllers/App.java public static void showUser(Long uid) { User u = ... List<Car> cars = ... renderArgs.put("user",u); render(cars, company, job, ...); } public static void showCar(Long id) {...} renderArgs.put(“cars”,car); renderArgs.put(“company”,company); renderArgs.put(“job”,job); same views/App/showUser.html Hello ${user.name} , these are your cars : #{list items:cars , as:'car'} #{a @showCar(car.id)} ${car.name} #{/a} #{/list} template tag @App.showCar(car.id)

76. How objects are passed to View !? controllers/App.java public static void showUser(Long uid) { renderArgs.put("user",u); render(cars , ...); } !!?? views/App/showUser.html ${user.name} #{list items:cars , as:'car'} Let's decompile it...

77. public static void showUser(Long uid) { play.classloading.enhancers.LocalvariablesNamesEnhancer.LocalVariablesNamesTracer.enter(); play.classloading.enhancers.LocalvariablesNamesEnhancer.LocalVariablesNamesTracer.addVariable("uid", uid); if(!play.classloading.enhancers.ControllersEnhancer.ControllerInstrumentation.isActionCallAllowed()) { Controller.redirect("controllers.App.showUser", new Object[] { uid }); } else { play.classloading.enhancers.ControllersEnhancer.ControllerInstrumentation.stopActionCall(); User u = (User)User.findById(uid); play.classloading.enhancers.LocalvariablesNamesEnhancer.LocalVariablesNamesTracer.addVariable("u", u); List cars = Car.all().fetch(); play.classloading.enhancers.LocalvariablesNamesEnhancer.LocalVariablesNamesTracer.addVariable("cars", cars); Object obj = null; play.mvc.Scope.RenderArgs renderargs = null; renderargs = (play.mvc.Scope.RenderArgs)Java.invokeStatic(Desc.getType("Lplay/mvc/Scope$RenderArgs;"), "current"); renderargs.put("user", u); render(new Object[] { cars }); } break MISSING_BLOCK_LABEL_120; Exception exception; exception; Object obj1 = null; play.classloading.enhancers.LocalvariablesNamesEnhancer.LocalVariablesNamesTracer.exit(); throw exception; Object obj2 = null; play.classloading.enhancers.LocalvariablesNamesEnhancer.LocalVariablesNamesTracer.exit(); return; }

78. Who Modifies My Code !? Who ? <ul><li>Play's custom classloader & JDT & javassist</li></ul>When ? <ul><li>DEV mode : When you modify the code and reload the page

79. PROD mode : App's start time</li></ul>How ? <ul><li>At compile time , some classes are enhanced by play.classloading.enhancers.* (powered by javassist)

80. ContinuationEnhancer

81. ControllerEnhancer

82. PropertiesEnhancer

83. LocalvariablesNamesEnhancer, ...</li></ul>Impact ? <ul><li>Rapid development time !</li></li></ul><li>View Template object path ${objectname} ${object.property} implicit objects ${params.userId} ${session.userId} ${request.userId} built-in tags #{if} ... #{/if} #{else}... #{/else} #{list items:users , as:'user'} ${user.name} #{/list} #{a @App.showUser(user.id)} show user #{/a} #{form @App.login() } ... #{/form}

84. Rich Domain Object Model package models; @javax.persistence.Entity public class User extends play.db.jpa.Model { public String username; public String password; } Support JPA's annotations : @Column , @ManyToOne , @OneToMany ... NO more getters & setters... Great !

85. Rich Domain Object Model BUT... The underlayer is hibernate & hibernate needs getter/setter Again... Who modifies my model ?

86. Rich Domain Object Model In Fact... Your model still contains getter/setter , modified by Play's custom classloader & JDT & javassist User.java public String getUsername() { return "overridden"; } ${user.username} will be ??

87. Rich Domain Object User u = User.findById(1); User u = User.find("byUsernameAndPassword", username , password).first(); User u = User.find("select u from User u where u.username = :username and u.password = :password") .bind("username",username) .bind("password",password) .first(); List<User> users = User.all().fetch(); User.em().createQuery(...);

88. Validations : Controller #{form @App.login()} username <input type=“text” name=“username” value=“${flash.username}” /> #{error 'username'/} password <input type=“password” name=“password” value=“${flash.password}” /> #{error 'password'/} <input type="submit" value=“Login" /> #{error ‘other'/} #{/form} username 請輸入帳號 password 請輸入密碼 Login 帳號或密碼輸入錯誤

89. Validations : Controller public static void login( @Required(message ="請輸入帳號")String username, @Required(message ="請輸入密碼")String password) { User user = User.login(username , password); if (validation.hasErrors()){ params.flash(); // add parameters to flash scope validation.keep(); // keeps the errors flash.error(validation.errors().get(0).toString()); render(“pleaseLogin.html”); } flash.success(“welcome : “ + user.username); render(); }

90. Validation : Model public class User extends Model { @Required @MinSize(6) public username; @Required @MinSize(6) public password; public static User login(String username , String password) { Validation validation = Validation.current(); User user = ... validation.isTrue(user!=null) .key(“other”).message(“帳號或密碼輸入錯誤”); return user; }} Will @MinSize affect login() ?

91. Validations @Required , @Min , @Max , @MinSize , @MaxSize , @Range , @Email , @URL ... Custom validation annotation extends AbstractAnnotationCheck & implements isSatisfied() i18n messages /conf/messages

92. Cache Conventional JavaEE's Way public User getUser(String name) { Session s = (Session)em.getDelegate(); Criteria c = s.createCriteria(User.class); c.add(Restrictions.eq("username",name); c.setMaxResults(1); c.setCacheable(true); if (c.uniqueResult() == null) return null; return (User) c.uniqueResult(); }

93. Cache Play's Way : Not In Favor of 2nd Level public static User getUser(String name) { String key="username_"+name; User user = Cache.get(key,User.class); if (user != null) return user; user = User.find("byUsername",name).first(); Cache.set(key,user,"30mn"); return user; }

94. Cache - Problem ! User.java { public static User getUser(Long id) { String key = "userId_"+id; ... } public static List<User> getUsers(Long page, int cnt) { String key="users_"+page+"_"+cnt; ... } } public interface UserDao.java { public User getUser(Long id); public List<User> getUsers(Long page, int cnt); }

95. Conventional JavaEE's Way User u1 = userDao.getUsers(1,10).get(0); User u2 = userDao.get(1L); assertTrue(u1.equals(u2)); // PASSED u2.modifySomething(...); userDao.save(u2); User u3 = userDao.getUsers(1,10).get(0); assertTrue(u3.equals(u2)); // PASSED Play's Way User u1 = User.getUsers(1,10).get(0); User u2 = User.getUser(1L); assertTrue(u1.equals(u2)); // PASSED u2.modifySomething(...); u2.save(); User u3 = User.getUsers(1,10).get(0); assertTrue(u3.equals(u2)); // FAILED!

96. Cache Problem : Reason users_1_10 cache key : TIME u u u u u u u u u u u1 userId_1 cache key : u modified / updated u2 users_1_10 cache key : ? u u u u u u u u u u3

97. Cache - Problem! How to Solve It ? <ul><li>Ignore it , accept it

98. Never cache sensitive data

99. Two phase list retrieval

100. Cache object ids instead of objects</li></ul>public static List<User> getUsers(Long page, int cnt) { String key="users_"+page+"_"+cnt; List<Long> userIds = User.find("select u.id from User u) .fetch(page,cnt); Cache.set(key, userIds, "1mn"); // iterate each id in result and query cache or fetch }

101. Cache : Wait... I saw Model.em() ? How about get underlaying Hibernate’s session and setCacheable(true) ? Session s = (Session) User.em().getDelegate(); Critieria c = s.createCriteria(...); c.add(... criterions ... ); c.setCacheable(true);

102. Play's Module System

103. Module : CRUD package models; public class User extends Model { ... } package controllers; public class Users extends CRUD { ... } Cars , Photos , Logs even ... Boxs , Buss, Kisss

104. Module GAE + Module Siena public class User extends siena.Model { public String uid; public static User getUser(String uid) { return User.all(User.class).filter("uid",uid).get(); } public static User getUsers(int page , int count) { return User .all(User.class) .fetch(count,(page-1)*count); } } Don't forget war/WEB-INF/appengine-web.xml $ play gae:deploy Done !

105. Play on GAE <ul><li>Simplest way to deploy Java Apps on GAE !

106. Shortest cold start time

107. Less than 10 seconds

108. Cache is wrapped to GAE's memcache

109. Mail is wrapped to GAE's mail service</li></li></ul><li>Issue : Portal-like Page <ul><li>Many blocks query DB in every page

110. Passing these query results in every action is cumbersome

111. Solution : @Before and renderArgs.put()</li></ul>@Before static void addDefaults() { renderArgs.put("brands", Brand.all().fetch()); renderArgs.put("forums", Forum.getAll()); renderArgs.put("tags" , Tag.getAll()); }

112. Issue : High Availability <VirtualHost *:80> ServerName myapp.com <Location /balancer-manager> SetHandler balancer-manager Order Deny,Allow Deny from all Allow from .myapp.com </Location> <Proxy balancer://mycluster> BalancerMember http://localhost:9002 BalancerMember http://localhost:9003 status=+H </Proxy> <Proxy *> Order Allow,Deny Allow From All </Proxy> ProxyPreserveHost on ProxyPass /balancer-manager ! ProxyPass / balancer://mycluster/ ProxyPassReverse / http://localhost:9002/ ProxyPassReverse / http://localhost:9003/ </VirtualHost> Apache Web Server localhost:9002 localhost:9003 Same directory structures & application.secret , only different http.port

113. Issue : Action Burst controllers/App controllers/App login() logout() register() myaccount() mybooks() index() page() search() showbook() login() logout() register() myaccount() mybooks() index() page() search() showBook() listUsers() editUser() editBook() controllers/Admin listUsers() editUser() editBook()

114. Issues : Validation Dilemma Validation in controllers ? validation in models ? or hybrid ?

115. Issue : DI Dependency Injection is not so useful in Play’s Rich Domain Object environment

116. Case Study : VAGTW.COM VW/Audi Car Problem Stats

117. vagtw.com Data Model

118. VAGTW.com development <ul><li>Dev in one month (Since 2010/4/1)

119. Modified from Play's YABE sample

120. 10 days learning Play! & modeling & coding

121. 20 days tuning HTML & CSS(3)

122. 2010/5/1 Debut

123. Peak 4x users in 15 mins

124. Indexed by Google in 2 days

125. Indexed by Yahoo in 2 weeks

126. Indexed by Bing after 2 months</li></li></ul><li>Conclusions IS ... <ul><li>A Glued Pure Web Framework

127. Loose

128. Shallow

129. non-Standardized

130. Page-based

131. Stateless</li></ul>IS-NOT ... <ul><li>A Java library

132. Full-Fledged JavaEE stack

133. Standard

134. Strict

135. Defined-assembled by interfaces

136. Component-based

137. Stateful (Session-aware)</li></li></ul><li>Conclusions : Use Play! If You... Have to prototype or build something quickly Don’t want to buy high-priced Java application servers Are not so OO-purism, feel OK without interfaces Many Play’s “hook” are not enforced by abctract mathods or interfaces Know JavaScript & other JS frameworks You can build slick UIs without sluggish server-state implementation responses (Wicket/JSF...) Feel OK about object inconsistences in cache Want to develop GAE apps Your team have a strong mendiator Because programming in play is too unrestrained Want to learn Scala

138. 小心 回不去了

Play! Framework for JavaEE Developers

Teng Shiu Huang

Play! Framework for JavaEE Developers