我有类似的问题，已经应用了各种尝试。以下是我通常的步骤：

I had similar problems and various attempts has been applied. Below is my usual steps:

1. 如果您使用Maven依赖关系，请转到Maven项目 - >刷新


2. 如果这不行，请尝试顶部菜单 - >构建 - >重建项目


3. 如果仍然无法使用，请尝试顶部菜单 - >文件 - >无效缓存/重新启动


4. 如果仍然不起作用，则$ CATALINA_BASE / bin / catalina.sh停止，然后开始

1. If you are using Maven dependencies, go to Maven Projects -> refresh
2. If that does not work, Try top menu --> Build --> Rebuild Project
3. If that still doesn't work, try top menu --> File --> Invalidate Cache/Restart
4. If that still doesn't work, then $CATALINA_BASE/bin/catalina.sh stop, then start

此后，通常覆盖99％的问题。否则，您可能还要检查其他一些可能性。

After this, usually it covers 99% of the problems. Otherwise, Probably you will have to examine some other possibilities.