public boolean isOpen(); public void close();
When an EntityManager is no longer needed, you should
call its close method. Closing an
EntityManager releases any resources it is using. The persistence
context ends, and the entities managed by the EntityManager
become detached. Any Query instances the
EntityManager created become invalid. Calling any method
other than isOpen on a closed EntityManager
results in an IllegalStateException. You
cannot close a EntityManager that is in the middle of a
transaction.
If you are in a managed environment using injected entity managers, you should not close them.