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

Question

我最近从GWT 2.0.4更新到了2.1.0。从那时起，我无法再编译GWT应用程序。当我单击GWT eclipse插件的GWT编译按钮时，出现以下错误：

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"

另外，我无法在Eclipse中创建新的GWT项目。在新的“新建Web应用程序项目”对话框中，可以选择使用GWT和/或Google App
Engine。选中“使用GWT”时，将弹出一个错误对话框，其中显示：“元素创建失败。原因：com.google.gwt.user.tools.WebAppCreator调用失败。有关更多详细信息，请参见错误日志。”

在日志文件（<workspace>/.metadata/.log）中，我可以看到以下消息：

!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和许多其他google-jar位于类路径中…

有谁知道如何解决这个问题？我还设置了一个新的全新Eclipse安装，安装了新的GWT插件，并选择了一个新的工作区目录，但这仍然给我错误。

附加信息：

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

Answer 1

我遇到同样的问题，无法在Eclipse中创建新的GWT项目。从我的Windows环境变量中删除Classpath变量（显然干扰了Eclipse中的设置）为我解决了这个问题。