GWT/Eclipse：ClassNotFoundException com/google/gwt/dev/Compiler
我最近从 GWT 2.0.4 更新到 2.1.0。从那时起我就无法再编译我的 GWT 应用程序了。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。当选中“使用 GWT”时，会出现一个错误对话框，其中显示： “创建元素失败。原因：调用 com.google.gwt.user.tools.WebAppCreator 失败。有关更多详细信息，请参阅错误日志。”
在日志文件 (
!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 都在类路径中...
有谁知道如何解决这个问题？ 我还设置了新的 Eclipse 安装，安装了新的 GWT 插件，并选择了新的工作区目录，但这仍然给我带来错误...
附加信息：
- Windows XP、
- Eclipse for Java EE 3.6 Helios、
- J2EE / Java 1.6 .0_22-b04
- Google Eclipse 插件 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
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
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评论（8）
我遇到了同样的问题，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（显然会干扰 Eclipse 中的设置）解决了我的问题。
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.
就我而言，从 google maven repo 下载的 jar (gwt-dev-2.1.0.jar) 已损坏！我将存储库中的 jar 替换为包含类的 jar，并且 mvn gwt:run 工作了！
希望这有帮助。
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.
我遇到了类似的问题，我不断收到 java.lang.NoClassDefFoundError: com/google/gwt/dev/Compiler。在四处搜索时，我意识到 gwt 版本缺少 gwt 安装目录内的 gwt-dev 文件夹中的文件。
实际上，我在项目中使用 maven 和 gwt 2.5.0，我发现 .m2\repository\com\google\gwt\gwt-dev\2.5.0 文件夹中应该存在四个文件，以便 gwt 编译器正常工作。
这些是
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
转到您的
项目属性/构建路径，将“GWT 库”移动到构建路径的顶部。现在再次尝试重新编译。
Go to your
Project Properties / Build Paththere move the "GWT library" to the top of the BuildPath.Now try to recompile again.
我只是删除并再次包含 gwt-dev.jar 并开始工作。
I just, remove and include again gwt-dev.jar and start to work.
我这样做解决了这个问题：
I fix that problem doing this:
我遇到了同样的问题，安装了一些java程序，声明了“ClassPath”环境变量，并使任何版本的eclipse（从3.6（helios）到4.2（juno））的gwt插件无效。
请注意，Windows 操作系统中的环境变量不区分大小写。
解决方案：消除系统/用户变量声明，并在相关程序的启动脚本中声明该变量。
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.
我的理解是：
当GWT编译一个项目时，它需要工具“com.google.gwt.dev.Compiler”（它有一个“main”入口点）；但是，GWT 不使用 Eclipse 项目的“构建路径”设置来查找该工具，而是查看操作系统的“类路径”系统变量。
所以，我认为解决方案是添加“D:\Java\GWT\gwt-2.6.1\*;” （以我的情况为例）进入“类路径”并重新启动 Eclipse。从那以后它对我来说效果很好。
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.