ID still null after persistent

trashhash · **Joined:** Thu Jan 11, 2007 11:27 am **Posts:** 11

Why is my object not update with given id after saving is to db? I have checked the table, and the new row is there but my object's id is still null.

Im using Mysql 5 and Annotations on id.

Code:

   @Id
   @GeneratedValue(strategy = GenerationType.AUTO)

Code:

Car car = new Car("Car Name");
em.persist(car);//table updated
System.out.println(car.getId()); // null

Thanks for your reply!

emmanuel · **Posted:** Thu Feb 15, 2007 8:29 pm

flush in between
or use session.save for such a semantic

trashhash · **Joined:** Thu Jan 11, 2007 11:27 am **Posts:** 11

Im getting the id from db, but only on the applicationserver, i dosent go back to the original object on the webserver. This must be an common problem in the EJB-world? Is there any sollutions for this? Or must i return the object i just saved?

Thanks for your reply!

trashhash · **Joined:** Thu Jan 11, 2007 11:27 am **Posts:** 11

Guess I'll have to figure this one out by my self. Thanks anayway.

emmanuel · **Posted:** Tue Feb 20, 2007 2:16 pm

I don't understand your question :-)
I *guess* the answer is that you need to flush before serializing your object.

sburkard · **Joined:** Sat Mar 24, 2007 1:10 pm **Posts:** 5

in opposite to hibernate, JPA does not update the original object instance after persisting. therefore you have to do

Car car = new Car("Car Name");
car = em.persist(car); // <-- notice the car =
out.println(car.getId());

regards
stefan

anthon.r · **Joined:** Fri Jan 27, 2006 4:20 am **Posts:** 22

emmanuel is right, you have to call the flush method after calling persist method.

Since you have GenerationType.AUTO, JPA needs to select the newly assigned ID (by mysql increment) by calling entityManager.flush() after calling persist. JPA will not know the newly assigned ID after you call the flush method since you delegated the ID assignment to MySQL.

bf65 · **Joined:** Wed Jul 16, 2014 3:17 pm **Posts:** 1

Stephan's suggestion worked for me. The persist or save method of my DAO returns the entity that I saved with the new Id.

Thanks!!

-------------------------------------------

in opposite to hibernate, JPA does not update the original object instance after persisting. therefore you have to do

Car car = new Car("Car Name");
car = em.persist(car); // <-- notice the car = the returned value from the persist method.....
out.println(car.getId());

regards
stefan