X cannot be added because it is already mapped to the entities. X entity class and the entity is not in current project source

问题

I'm creating a new NetBeans EE Enterprise Application, and when I try to create Entity classes from database (Customer from the sample database), I can't select it because of this error :

Any idea? I'm using NetBeans 7.3 with Glassfish 3.1.2.

回答1:

I found the answer after spending the last few hours searching in Google. Delete the cache folder in the following

C:\Users\yourusername\AppData\Local\NetBeans\Cache

It solved the problem for me.

回答2:

In case of NetBeans for Linux the answer of @Lawrence Wong applies too; but the cache folder is located in ~/.cache/netbeans (at least in Fedora).

In my case, the problem was probably caused by assigning an Entity Class from a database in a test project that no longer exists.

来源：https://stackoverflow.com/questions/21207398/x-cannot-be-added-because-it-is-already-mapped-to-the-entities-x-entity-class-a