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Firstly i would like to apologize if i could not find anything about what i would like to describe that really solved my problems. This does not mean that i fully searched in the site. Although i have been spending too much time (days). I am also new on here (in the sense that i never wrote/replied to SO users). And i am sorry for my possible english errors.

I have to say i am new to Java EE. I am working on WildFly 14, using MySQL. I am now focusing on a JPA problem. I have a uniqueness constraint. I am doing tests and while performing the uniqueness violation test, from the data source level i get a MySQLIntegrityConstraintViolationException, and that's ok. I have the problem in that the persist() method does not let me catch the exception (i even put Throwable in the clause, but nothing..). I strongly, strictly, need to catch that, in order to manage a crucial procedure (that, indirectly contains the call to .remove()) in my work's code.

By the way, trying to write that exception, the system does not show me the window of the suggested classes/annotations/etc, suggesting me just to create the class "MySQLIntegrityConstraintViolationException". Doesn't working on WildFly, using MySQL, suffice, for having the suggestions?

Not finding the solution, i decided to change: instead of using persist(), i decided to use .createNativeQuery() in which i put as parameter a String describing an insertion in the db. It seems working. Indeed it works (signals uniqueness violation (ok!), does not execute the TRY block code (ok!) and goes into CATCH block (ok!)). But, again, the exception/error is not clear. Also, when in the code i enter the piece of code that is in charge of managing the catching and then executing what's inside (and i have a .remove(), inside), it raises the exception:

"Transaction is required to perform this operation (either use a transaction or extended persistence context)" --> this referring to my entityManager.remove() execution..

Now i cannot understand.. should not JPA/JTA manage automatically the transactions?

Moreover, trying, later, to put entityManager.getTransaction().begin() (and commit()), it gives me the problem of having tried to manage manually transactions when instead i couldn't.. seems an endless loop..

[edit]: i am working in CMT context, so i am allowed to work with just EntityManager and EntityManagerFactory. I have tried with entityManager.getTransaction().begin() and entityManager.getTransaction().commit() and it hasn't worked.

[edit']: .getTransaction (EntityTransaction object) cannot be used in CMT context, for this reason that didn't work.

[edit'']: i have solved the transaction issue, by means of the transaction management suited for the CMT context: JTA + CMT requires us to manage the transactions with a TRY-CATCH-FINALLY block, in whose TRY body it is needed to put the operation we want to perform on the database and in whose FINALLY body it is needed to put the EntityManager object closing (em.close()). Though, as explained above, i have used em.createNativeQuery(), that, when failing, throws catchable (catchable in my app) exceptions; i would really need to do a roll-back (usage of .createNativeQuery() is temporary) in my work code and use the .persist() method, so i need to know what to do in order to be able to catch that MySQLIntegrityConstraintViolationException.

Thanks so much!

tcoddis
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1 Answers1

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IT SEEMS i have solved the problem.

Rolling back to the use of .persist() (so, discarding createNativeQuery()), putting em.flush() JUST AFTER em.persist(my_entity_object) has helped me, in that, once the uniqueness constraint is violated (see above), the raised exception is now catchable. With the catchable exception, I can now do as described at the beginning of the post.

WARNING: I remind you of the fact that i am new to JavaEE-JPA-JTA. I have been "lucky" because, since my lack of knowledge, i put that instruction (em.flush()) by taking a guess (i don't know how i could think of that). Hence, I would not be able to explain the behaviour; I would appreciate, though, any explanation of what could have happen, of how and when the method flush() is used, and so on and so forth..

Thanks!

tcoddis
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