GWT/ Eclipse: ClassNotFoundException com/google/gwt/dev/Compiler

Question

i recently updated from GWT 2.0.4 to 2.1.0. Since then I cannot compile my GWT application anymore. When I click on the GWT compile button of the GWT eclipse plugin I get the following error:

java.lang.NoClassDefFoundError: com/google/gwt/dev/Compiler
Caused by: java.lang.ClassNotFoundException: com.google.gwt.dev.Compiler
 at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
 at java.security.AccessController.doPrivileged(Native Method)
 at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
 at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
Exception in thread "main"

Also I can't create a new GWT project in Eclipse. In the new New Web Application Project Dialog one can choose to use GWT and/or Google App Engine. When check "Use GWT" a error dialog raises up which says: "Creation of element failed. Reason: Invocation of com.google.gwt.user.tools.WebAppCreator failed. See the error log for more details."

In the log file (<workspace>/.metadata/.log) I can see the message:

!ENTRY org.eclipse.jdt.ui 4 10001 2010-11-02 08:34:50.085
!MESSAGE Internal Error
!STACK 1
Java Model Exception: Core Exception [code 0] Invocation of com.google.gwt.user.tools.WebAppCreator failed. See the error log for more details.
 at org.eclipse.jdt.internal.core.BatchOperation.executeOperation(BatchOperation.java:50)
 at org.eclipse.jdt.internal.core.JavaModelOperation.run(JavaModelOperation.java:728)
 at org.eclipse.core.internal.resources.Workspace.run(Workspace.java:1975)
 at org.eclipse.jdt.core.JavaCore.run(JavaCore.java:4777)
 at org.eclipse.jdt.internal.ui.actions.WorkbenchRunnableAdapter.run(WorkbenchRunnableAdapter.java:106)
 at org.eclipse.jface.operation.ModalContext$ModalContextThread.run(ModalContext.java:121)
Caused by: org.eclipse.core.runtime.CoreException: Invocation of com.google.gwt.user.tools.WebAppCreator failed. See the error log for more details.
 at com.google.gwt.eclipse.core.runtime.tools.WebAppProjectCreatorRunner.createProject(WebAppProjectCreatorRunner.java:53)
 at com.google.gdt.eclipse.suite.wizards.WebAppProjectCreator.createGWTProject(WebAppProjectCreator.java:532)
 at com.google.gdt.eclipse.suite.wizards.WebAppProjectCreator.create(WebAppProjectCreator.java:294)
 at com.google.gdt.eclipse.suite.wizards.NewWebAppProjectWizard.finishPage(NewWebAppProjectWizard.java:147)
 at org.eclipse.jdt.internal.ui.wizards.NewElementWizard$2.run(NewElementWizard.java:117)
 at org.eclipse.jdt.internal.core.BatchOperation.executeOperation(BatchOperation.java:39)
 at org.eclipse.jdt.internal.core.JavaModelOperation.run(JavaModelOperation.java:728)
 at org.eclipse.core.internal.resources.Workspace.run(Workspace.java:1975)
 at org.eclipse.jdt.core.JavaCore.run(JavaCore.java:4777)
 at org.eclipse.jdt.internal.ui.actions.WorkbenchRunnableAdapter.run(WorkbenchRunnableAdapter.java:106)
 at org.eclipse.jface.operation.ModalContext$ModalContextThread.run(ModalContext.java:121)
!SUBENTRY 1 com.google.gwt.eclipse.core 4 0 2010-11-02 08:34:50.085
!MESSAGE Invocation of com.google.gwt.user.tools.WebAppCreator failed. See the error log for more details.

gwt-dev.jar, gwt-user.jar and many other google-jars are in the classpath...

Does anyone have an idea how to solve this issue? I also set up a new fresh Eclipse installation, installed the new GWT plugin, and chose a new workspace directory, but this still gives me the errors...

Additional information:

• Windows XP,
• Eclipse for Java EE 3.6 Helios,
• J2EE / Java 1.6.0_22-b04
• Google Plugin for Eclipse 3.6 1.4.0.v201010280102,
• Google App Engine Java SDK 1.3.8 1.3.8.v201010161055
• Google Web Toolkit SDK 2.1.0 2.1.0.v201010280102

Kevel

Answer 1

I had the same problem not being able to create a new GWT-project in Eclipse. Removing the Classpath variable from my windows environment variables (appearently interfering with the settings in Eclipse) solved the problem for me.

Marital

Thank you! That did the trick! Unfortunatly I run into another problem: [ERROR] Unable to find 'GWTModule/gwt/xml.gwt.xml' on your classpath; could be a typo, or maybe you forgot to include a classpath entry for source? Looks like somtehing got messed up when I was playing around with different GWT versions. – Kevel

Answer 2

In my case the jar (gwt-dev-2.1.0.jar) downloaded from the google maven repo was corrupt! I replace the jar in my repo with a one containing the classes and mvn gwt:run worked!

hope this helps.

Papp

I don't use maven. I installed the gwt plungin direclty from the gwt update site... i tried to reinstall the plugin, replace the plugin gwt-sdk with one downloaded from the google page but all didn't help. :( – Kevel

I experienced the exact same issue. My JAR contained HTML. Redownloading fixed this. At some point someone must've messed something up with the repository we are/were using. – Apollo

Answer 3

I was facing a similar issue where I was getting constantly java.lang.NoClassDefFoundError: com/google/gwt/dev/Compiler. While searching around I realized that the gwt version was missing a file from inside the gwt-dev folder inside the gwt installation directory.

Actually, I am using maven and gwt 2.5.0 for my project, and I discovered that inside .m2\repository\com\google\gwt\gwt-dev\2.5.0 folder should exist four files in order for gwt compiler to work. Those are

• gwt-dev-2.5.0.jar <-sometimes this is corrupted
• gwt-dev-2.5.0.jar.sha1 <- this one was missing
• gwt-dev-2.5.0.pom
• gwt-dev-2.5.0.pom.sha1

Strobe

Answer 4

Go to your Project Properties / Build Path there move the "GWT library" to the top of the BuildPath.

Now try to recompile again.

Tritium

Unfortunately that didn't help. My classpath order now is: GWT SDK, jdk, glassfish libs, a lot of other jars, my project directory But I still get the NoClassDefFoundError and I can't create a new GWT project. I will now try to set up a completely new environment in a VM... – Kevel

The upgrade to 2.1 is a bit painful. I had problems in my 2 computers. Moving the GWT in the buildpath helped in both systems, but in one I also needed to clear all the cached files. In my OSX I even needed to restart completely the computer (for some weird reason) – Tritium

Answer 5

I just, remove and include again gwt-dev.jar and start to work.

Lentha

Answer 6

I fix that problem doing this:

• remove GWT lib from your project
• update gwt plugins for eclipse
• put the lib back in your project
• Done

Lacedaemonian

Answer 7

I had the same problem, some java program had been installed declaring a "ClassPath" environment variable, and invalidating the gwt plugin for ANY version of eclipse, from 3.6 (helios) to 4.2 (juno). Note that environment variables are case-insensitive in Windows OSs. Solution: eliminate the system/user variable declaration and declare the variable in a/the launch script for the concerned program.

Fustian

Answer 8

My understanding is:

When GWT compiles a project, it needs the tool "com.google.gwt.dev.Compiler" (which has a "main" entry point); however, GWT does not use Eclipse project's "build path" setting to find the tool, instead, it looks at OS's "classpath" system variable.

So, I think the solution is to add "D:\Java\GWT\gwt-2.6.1\*;" (my case as example) into "classpath" and restart Eclipse. It works well for me since.

Danilodanio