1. Apache Wicket: web applications with just Java Xavier Hanin JavaZone ‘07

2. Who is Xavier Hanin Independent Java Consultant Customers Open Source Renault

3. Agenda What is Wicket Core concepts of Wicket Developing a custom component Q&A

4. Wicket in a Nutshell Open Source (Apache Software Foundation) Component based Pure Java + Pure HTML Simple Enthusiastic community

5. What is Wicket? The technology: enabling component- oriented, programmatic manipulation of markup The mission: bringing object oriented programming to the web application view layer The reward: have a fun job and be good friends with your manager again

6. Achieving these goals through Keeping simple things simple Utilizing an object-oriented component model where components are truly self contained Re-applying the Model View Controller pattern on components instead of requests, with models as first class citizens Having a clean separation of concerns between HTML and Java

7. Achieving these goals through Providing transparent, fully automated state management Keeping configuration needs to the minimum No more XML! Making using & creating custom components easier than any framework out there

8. Component versus ‘traditional’ Traditional –Struts, WebWork, Spring MVC, etc. –Proven for web –A lot of web developers available Components –JSF, Wicket, Tapestry, etc. –Traditional model for UI development on thick clients –A lot of developers available

9. Features Page composition –panels, borders and markup inheritance Excellent localization and style support –template and resource loading (_be.html,.xml) –localized models (e.g. for labels) –sophisticated resource bundle lookup (composition & inheritance hierarchy) –automatic client capabilities detection

10. Features Integration –Spring –Guice –Hibernate –JasperReports –OSGi Fancy components –sortable, filterable, pageable, data aware tables –date picker, rich text editor, Google Maps –tabbed panel, navigation, tree, wizard

11. Features State management –type safe sessions clustering support back button support Double submit strategies –render redirect/ redirect to buffered response/ none Testing support –JUnit testing extensive logging and error reporting

12. Features Ajax support and components –Ajax without writing JavaScript, Dojo, Scriptaculous,... Header contribution –Javascript & CSS URL mounting –pretty URLs Component level security

13. Agenda What is Wicket Core concepts of Wicket Developing a custom component Q&A

14. Wicket’s concepts Application Session RequestCycle Components Behaviors Models

15. Application Main entry point for your web application Configuration –Output Wicket specific tags? –Watch for markup changes every …? –Defines homepage Factories for –Session –RequestCycle –Security –…

16. Application Configured in web.xml: wicket org.apache.wicket.protocol.http.WicketFilter applicationClassName example.MyApplication 1

17. Wicket’s concepts Application Session RequestCycle Components Behaviors Models

18. Session Abstraction of a user session Storage typically in HttpSession Stores session specific data –Locale, Client info (browser vendor and version) –Your own data? Logged in user Shopping cart contents –Limited page history for back button support

19. Session class MySession extends WebSession { private ShoppingCart cart; public ShoppingCart getCart() { … } public void setCart(ShoppingCart cart) { … } } mysession.setCart(new ShoppingCart()); … ShoppingCart cart = mysession.getCart(); cart.add(quantity, selectedProduct);

20. Wicket’s concepts Application Session RequestCycle Components Behaviors Models

21. RequestCycle Steps in a request cycle: 1.Create request cycle object 2.Decode the request 3.Identify request target (page, component, …) 4.Process event (onClick, onSubmit, …) 5.Respond (page, component, image, pdf, …) 6.Clean up

22. RequestCycle Two types of requests: –Stateful Tied to specific user session Not bookmarkable –Stateless Not necessarily tied to specific user session Bookmarkable

23. Wicket’s concepts Application Session RequestCycle Components Behaviors Models

24. Components encapsulate the programmatic manipulation of markup can receive an event –onClick, onSubmit know how and where to render itself

25. Component Ultimate super class wicket.Component –Label –MultiLineLabel –TextField –PasswordTextField –Image –Link –Tree –BookmarkablePageLink –JasperReports –ListView –Loop –PagingNavigator –ImageMap –Button –Ajax… –Sorting, paging repeaters –Wizard –DatePicker

26. Components and markup A component is identified in markup with wicket:id Html: Gets replaced Java: new Label(“msg”, “Hello, World!”); Final (wicket tags can be stripped): Hello, World!

27. Components and markup Component can have its own markup file –Page –Panel –Border Put java, markup and supporting files in same package on class path

28. A page: Hello, World!

29. Wicket’s concepts Application Session RequestCycle Components Behaviors Models

30. Behaviors Behaviors are plug-ins for Components They can modify the components markup item.add(new AbstractBehavior() { public void onComponentTag( Component component, ComponentTag tag) { String css = (((Item)component).getIndex() % 2 == 0) ? "even" : "odd"; tag.put("class", css); } }); Output: … …

31. Behaviors Change attributes of your component’s markup Add javascript events Add Ajax behavior component.add( new AjaxSelfUpdatingBehavior( Duration.seconds(1)));

32. Wicket’s concepts Application Session RequestCycle Components Behaviors Models

33. Models bind your POJO’s to Wicket components Label(“name”, model) > +name : String +city : String PropertyModel

34. Models Lazy binding in Java sucks –Doesn’t update: new TextField(“txt”, person.getName()) –Gives null pointers: new Label(“street”, person.getAddress().getStreet()) Solution: OGNL/EL like expressions

35. Models PropertyModel: –new PropertyModel(person, “name”) –new PropertyModel(person, “address.street”) Be aware for nulls when using updates: Person p = new Person(); new TextField(“street”, new PropertyModel(p, “address.street”));

36. Agenda What is Wicket Core concepts of Wicket Developing a custom component Q&A

37. Why a custom component? Eelco Hillenius: « Imagine being told that you can use Java as your programming language, but at the same time being told not to create your own classes. [...] I fail to understand why that has to be different for UI development, and Wicket proves it doesn't have to be so. »

38. Custom components for all 464 pages 20 minutes

39. Example: Password strength weak medium strong

40. Components Creating custom component is as easy as typing in ‘extends’ Extends wicket.Component down the line Available on application classpath

41. Example: Password strength Panels provide grouping –Have own markup file –Can be exchanged in pages for other components –Can contribute to header –Can contain any number of components, including panels

42. Example: Password strength

45. Components are reusable Put them in a JAR Package all necessary resources: –HTML, JavaScript, Images, CSS –class file Put JAR on classpath Ready for (re)use

46. Conclusion Smart component oriented web framework Easy creation and use of custom components Enthustiatic community Join in! http://wicket.apache.org/ users@wicket.apache.org

47. Agenda What is Wicket Core concepts of Wicket Developing a custom component Q&A