JPA when update entity

Question

I have an method in DAO like below,

public void updateEntity1(Entity2) {
     Entity1 = entitymanager.find(....);
     Entity1.setAttr(Entity2.getAttr());
     .........
     entitymanager.merge(Entity1);
     em.flush();
}

I want update entity1 with the value entity2 contains, at the end of the method, I find entity1's attr updated successfully, but the in database it didn't changed? Is there any thing wrong with this method?

Answer 1

Try enclosing your code by in a transaction as below:

entityManager.getTransaction().begin();
....//your code
entityManager.getTransaction().commit();

Answer 2

If your transaction is already available (otherwise try @Madhusudana Reddy Sunnapu solution) try with:

public void updateEntity1(entity2) {
     Entity1 entity1 = entitymanager.find(...);
     Entity1.setAttr(entity2.getAttr());
     ...
     entity2.detach();
     entitymanager.merge(entity1);
     em.flush();
}

Answer 3

thanks for help. I find out the interesting reason, it is about the search cache:

the Entity1 was in cache due to a former search, eg it's attr=1;

but in another transaction, it's attr was setted to 2, so the cache data is dirty data,

above I just want to set Entity1 attr back to 1,but the cache data is still 1, so JPA thought I didn't make any change, so em.merge() do nothing.

that's quite impressive!