Google Web toolkit
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The document discusses the Google Web Toolkit (GWT), which allows developers to build Ajax applications in Java that are compiled into JavaScript for cross-browser support. It addresses some common architectural issues with Ajax apps that GWT handles, such as back button support, session state, and UI event handling. The author provides an overview of GWT features and demos building widgets and applications. Gotchas discussed include RPC only working with GWT clients and needing to replace hibernated objects before serialization to avoid memory leaks.
Google Web toolkit
- 1. Building Ajax Applications with the Google Web Toolkit Vivek Prahlad
- 2. Agenda What is the Google Web Toolkit? Features Architectural issues with AJAX applications And how the GWT handles them Experience report: What went well? Gotchas Lots of demos
- 3. What is the GWT? A UI framework for building Ajax apps in Java Best suited for one page Ajax apps Can be embedded into existing apps as well Open Source (Apache 2 license) Component based programming model Similar to, but simpler than Swing / SWT Control application appearance via CSS Simple RPC framework
- 4. Source: Adaptive Path How are Ajax apps different?
- 8. Developing applications Client side code: Java + GWT UI library Restriction: subset of the JDK – java.lang, java.util Compiled to javascript. Morfik, Script# are similar Server side code: GWT RPC + usual suspects Spring & Hibernate Can send domain layer classes over the wire Need to implement IsSerializable Compiled to bytecode as usual
- 9. Features Component based framework Browser support: IE6+, Firefox, Mozilla, Safari, Opera No Konqueror support Internationalization Debugging Browser history management Integrate with javascript libraries via JSNI JUnit integration
- 11. Architectural Issues? Back button support? Handled by the browser Session state? All on the client, not a server issue UI event handling? All on the client, no round trip Deployment? Compiled Javascript code, java on server side
- 12. Answers to a few Ajax headaches History? Handled by the History class Cross browser support? Abstract DOM class RPC? Java based RPC mechanism
- 13. Building Widgets Build new widgets from existing ones Style with CSS No, your app doesn't have to look like Gmail! Layout with panels
- 14. Testing Sahi ( http://sahi.co.in ) for functional testing Unit testing via the GWTTestCase Same restrictions as with UI code MVC is your friend Use GWTTestcase for the view Test the Model and Controller as usual
- 15. What went well? Truly cross-browser App needed 2 lines of custom javascript For disabling text selection Great component model Easy to build custom components from scratch Java to Javascript compiler works like a charm No memory leaks Break up large apps with modules & IFrames
- 16. Gotchas RPC mechanism works only with GWT clients Some widgets use HTML tables internally CSS for layout faster, but more challenging Table widget support weak No MVC separation
- 17. Gotchas Need to be careful about client side state Ajax apps usually long lived – memory leaks can kill you Some widgets need a lot of custom HTML Tree widget biggest offender Need to replace hibernated objects before serializing Replace PersistentSet, PersistentList with HashSet, ArrayList
- 18. Resources http://code.google.com/webtoolkit http://groups.google.com/Google-Web-Toolkit http://www.adaptivepath.com/publications/essays/archives/000385.php
- 19. Questions?