Link:
http://stackoverflow.com/questions/3701901/eclipse-does-not-recognize-content-of-persistence-xml
引用：
I fixed the problem the following way (I'm using RAD v8.5.1):
. Windows --> Preferences --> Validation
. Scroll down to "JPA Validator" and click on the Ellipses under Settings.
. Click on the "Add Include Group..." button.
. Click on the new Include Group that appeared to highlight it.
. Click on the "Add Rule..." button.
. A dialog menu pops up. Click the "Folder or file name" radio button and click on "Next".
. Click on "Browse Folder..." and navigate to your src directory (in my case, it was "src/main/resources") within your project (my project was a .war in a multi module app) in your workspace.
. Click on "Finish".
. Click on "OK". This will prompt a full build.
The error will go away.