Today when writing about the entity persisting code, I become confuse.

I referred to the hibernate manual, so I do not take too much further.

I am still wondering using JPA's entity manager or the session factory
base on hibernate. Originally, the context.xml has setup the JPA
procedure, but I am not sure about how to write the elegant and
effective code.

Same as yesterday, hoping I can handle JPA quickly.

Signed-off-by: winguse <github@winguse.com>