Sunday, 9 October 2011

GWT, GXT and Compilation Problem

I found an excellent book that finally explained me the differences between a number of extensions to Google Web Toolkit, and served as an excellent introduction into Ext GWT, a.k.a. GXT.

I started playing with the framework, and it is powerful and beautiful. It seemed to be quite sluggish when developing locally, but when deployed to the server it works much better, I don’t see any problems with performance.

However, my first attempt to deploy my project to the AppEngine wasn’t successful, I’ve got a rather esoteric error message:

java.lang.IncompatibleClassChangeError: Found interface, but class was expected

Fortunately, there is already a raised issue for this. It looks like after GWT reached version 2.2, a number of other solutions became incompatible with it, and that seems to be the case with GXT as well.

The solution was to downgrade GWT to version 2.1. Then I had to replace this line of code in the project’s module:

<inherits name=''/>

with this one:

<inherits name=''/>

After this, the project has deployed successfully. However, today I tried to run it locally, and GWT plugin in the browser can’t connect to the local server. I guess the reason is that I downgraded the GWT itself but haven’t downgraded the plugin. A bit of a mess.

I’ll need to tell the GXT folks about this problem when I have more time.

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