java - : "Loading descriptor for . .. java.lang.NullPointerException 期间发生内部错误

Question

每当我刷新动态 Web 项目(或保存文件)时，都会出现错误。实际上，它通常会显示相同的错误三次。

我在这里查看的其他答案表明，只有当该人创建新项目时才会发生这种情况。这种情况最近才开始发生。

查看workspace/.metadata/.log 会发现一系列错误:

!ENTRY org.eclipse.jst.j2ee 4 0 2015-05-15 15:20:16.141
!MESSAGE No IModelProvider exists for project P/MyWebProject of version: Dynamic Web Module 2.5
!STACK 0
java.lang.NullPointerException: No IModelProvider exists for project P/MyWebProject of version: Dynamic Web Module 2.5
    at org.eclipse.jst.j2ee.model.ModelProviderManager.getModelProvider(ModelProviderManager.java:101)
    at org.eclipse.jst.j2ee.model.ModelProviderManager.getModelProvider(ModelProviderManager.java:281)
    at org.eclipse.jst.jee.ui.internal.navigator.JEE5ContentProvider.getCachedModelProvider(JEE5ContentProvider.java:76)
    at org.eclipse.jst.jee.ui.internal.navigator.Web25ContentProvider.getNewContentProviderInstance(Web25ContentProvider.java:69)
    at org.eclipse.jst.jee.ui.internal.navigator.LoadingJeeDDJob.run(LoadingJeeDDJob.java:50)
    at org.eclipse.core.internal.jobs.Worker.run(Worker.java:53)

!ENTRY org.eclipse.core.jobs 4 2 2015-05-15 15:20:16.141
!MESSAGE An internal error occurred during: "Loading descriptor for MyWebProject.".
!STACK 0
java.lang.NullPointerException
    at org.eclipse.jst.jee.ui.internal.navigator.JEE5ContentProvider.getCachedModelProvider(JEE5ContentProvider.java:77)
    at org.eclipse.jst.jee.ui.internal.navigator.Web25ContentProvider.getNewContentProviderInstance(Web25ContentProvider.java:69)
    at org.eclipse.jst.jee.ui.internal.navigator.LoadingJeeDDJob.run(LoadingJeeDDJob.java:50)
    at org.eclipse.core.internal.jobs.Worker.run(Worker.java:53)

Answer 1

这个问题以多种形式出现，例如
Error when creating a new Vaadin project in eclipse

解决方案:安装这些:

• Eclipse Java EE 开发人员工具
• Eclipse Java Web 开发人员工具
• JST 服务器适配器
• JST 服务器适配器扩展

(在我的例子中，缺少 Eclipse Java Web Developer Tools。)