Running GWT 2.4.0 with STS 2.9.1 and Grails 2.0.3

Alright, if you followed all the steps of the previous post, you should be able to see the results of the GWT code execution at the address:

http://localhost:8080/{projectname}/hello.gsp 

As you might have noticed, I previously asked the plugin to compile the GWT code (compile-gwt-modules). That operation takes some seconds as the entire artifact is recompiled (when the application will grow, the compilation can last minutes).  Luckily there is an alternative, the hosted mode. When an application is running in hosted mode, the Java Virtual Machine (JVM) is actually executing the application code as compiled Java bytecode, using GWT plumbing to automate an embedded browser window. This means (1) we don't need to recompile the code as STS is producing the Java bytecode for us incrementally (2) the debugging facilities of your IDE are available to debug both your client-side GWT code and any server-side Java code as well.

First we start the grails application (run-app), second, in the command prompt we type:

run-gwt-client

This last command starts the hosted mode and you should see appearing a window like the one depicted in figure 1. 

Figure 1: hosted mode window.

Now we can 'copy to clipboard' and open that link in a web browser:

http://localhost:8080/GwtTest/hello.gsp?gwt.codesvr=127.0.0.1:9997

The page should appear in the window and the alert 'hello' should display. Now you can verify the usefulness of the hosted mode by updating the alert - in the class HelloApp.java from 'hello' to 'hello me' - and reloading the page. The alert will display the new string without you having to trigger the GWT code compilation manually. And this will result in a huge save of time. (Read more)

Note. Remember that the manual compilation is still necessary prior to deployment as the deployed version of the page will run the compiled JavaScript.