greetings!

to put this simple, let's see a example:

Party p = em.find(Party.class, id)
PartyDetails pd = new PartyDetails;

...

// a party can have multiple details, and order number is maintained to
// connect with the latest version of details

pd.setParty(p);
p.setOrderNumber(p.getOrderNumber()+1);
pd.setOrderNumber(p.getOrderNumber());

...

so to save changes on p object practically i have to do nothing more, and to save new pd object all i have to do is em.persist(pd) and wait for transaction to happen. but what if i want to discard changes? in that case i wouldn't call persist for pd object. but can i undo the changes i made on the existing entity - p without having to retrieve data from database but simply removing it from the context.

thanks

This isn't quite an answer to your question, but something to think about.

After doing the initial persisting of the object, you could evict the POJO. Then, changes that happen after the evict are not applied. Then, if you do want to apply the changes, you just update or save the evicted POJO, making it a persistent object again.

So, it doesn't really reverse the update, but instead, it reverses the reversal of the reversal. :)

Just another way of thinking about it, without rolling back transactions or getting into tricky situations like that.

very nice, but how do i evict an entity? i guess this is not ejb standard. is it compatible with seam-controlled entity manager and conversational transaction demarcation?

i found the solution.

Session session = (Session)em.getDelegate();
session.evict(myEntity);

the thing i cannot understand is why it isn't a part of EnitityManager API because it's functionality is so basic and needed.

For those playing the Hibernate3 home game, here's the Java Doc:



http://www.hibernate.org/hib_docs/v3/api/org/hibernate/Session.html#evict(java.lang.Object)