8.11.1 Notes on allocating the entity classes
With Application Server, package the entity classes in the EARs, EJB-JARs, or WARs, at the locations decided in the JPA specifications. Do not add the entity classes in the system class path.
When an entity class is loaded with the application class loader or the Web application class loader, the byte code of the class is converted using the JPA provider in order to implement operations such as Lazy fetch. If the entity class is included in the system class path, the byte code conversion does not work because the entity class is loaded with the system class loader. Therefore, the JPA provider does not operate properly.