Few days ago I found some classes ended in ‘_’ char, all this classes had the same name of my entity classes. After much wasted time, I finally found the problem, and it’s on Eclipse project configuration.
The JPA support has many options to manage and help your JPA projects, but if you don’t use it, sometimes some configuration can be bigger butt. To solve this, go to Project properties (Alt + Enter), then go to JPA tab, then set Canonical Metamodel to ‘None’, like this:
Now, just remove your ‘_’ classes and rebuild your project.
References
http://stackoverflow.com/questions/1158159/no-persistence-provider-for-entitymanager-named