This post will explain the cause of this exception and provide an easy fix – with no need to add extra jars to your classpath or manually manipulate your jars.

I first saw this exception when I upgraded a project from GWT 2.4 to GWT 2.5.

The project also uses GXT 2 and 3 running side by side.

After the upgrade I saw this in the logs:


Caused by: java.lang.NoClassDefFoundError: com/google/gwt/core/client/GWTBridge
at com.extjs.gxt.ui.client.core.FastMap.<init>(

TL;DR version:

Add the below  in your project (make sure the package is right):


* Date: 1/17/13
* Time: 12:37 PM
* This class is used for fixing class not found;
* This is only needed for GXT 2 to work. Once we remove GXT2, this can be removed also.
public abstract class GWTBridge extends {

Long version:

This is the issue in which Google is tracking this:
Status is: fixed, not released. It will be released in 2.5.1 it seems.

FastMap class from GXT2 uses GWT.isScript() method to figure out if it’s running in a JS form, or a Java-translated form.

The issue is that GWT class from the client package, has a method called:  setBridge, with a GWTBridge as a parameter, but no import.

So the classloader searches for GWTBridge, inside, but there is no class there.
This is the GWT class from 2.5.0:

The fix just adds it in the package in which the classloader is looking. As you can see it doesn’t change it in any way.

Hope this helps.