eclipse 在以下过程中发生内部错误：“正在为 ... java.lang.NullPointerException 加载描述符
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An internal error occurred during: "Loading descriptor for ... java.lang.NullPointerException
提问by dwjohnston
When ever I refresh my Dynamic Web Project (or save a file), it gives met his error. It actually usually displays the same error three times.
当我刷新我的动态 Web 项目（或保存文件）时，它会遇到他的错误。它实际上通常会显示三次相同的错误。
The other answers I've looked at here suggest it only happens when the person creates a new project. This has started happening just recently.
我在此处查看的其他答案表明它仅在此人创建新项目时发生。这是最近才开始发生的。
Looking at the workspace/.metadata/.log shows me a range of errors:
查看工作区/.metadata/.log 向我展示了一系列错误：
!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)
采纳答案by dwjohnston
Deleting the project and rechecking it out solved this problem.
删除项目并重新检查它解决了这个问题。
回答by MGM
This problem had occurred in many forms, e.g.
Error when creating a new Vaadin project in eclipse
这个问题出现的形式很多，比如
在eclipse中新建一个Vaadin项目时出错
Solution: install these:
解决方案：安装这些：
- Eclipse Java EE Developer Tools
- Eclipse Java Web Developer Tools
- JST Server Adapters
- JST Server Adapters Extensions
- 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
(In my case, Eclipse Java Web Developer Tools was missing.)
（就我而言，缺少 Eclipse Java Web Developer Tools。）
回答by Jeyam Venkat
Your web.xml will be in error. Check for any servlet mapping for an invalid class and remove the mapping and clean your project .
您的 web.xml 将出错。检查无效类的任何 servlet 映射并删除映射并清理您的项目。
