Hello,

In Hibernate documentation I found that: "Currently, the specified value of the unique-key attribute is not used to name the constraint in the generated DDL". But is it possible to name unique constraint?

I like to catch ConstraintViolationException and from it get to know which constraint was violated - is it userId, is it userAlternateLogin or something else. It would be great to now it from exception. As a workaround I catch this exception and then I check if there is userId already used or maybe userAlternateLogin is already used or... But it is inconvenient.

Thanks for any help with this issue.

P.S. I've searched documentation, googled many pages and I did not find the answer.

Hello,
after hibernate throws a runtime exceptions, session becomes non-usable, you have to roll back the transaction and also close current session. ConstraintViolationException is wrapped in a RuntimeException. Exceptions thrown by hibernate are considered fatal, you would see the message though telling you which constraint was violated.

But in ConstraintViolationException is method "getConstraintName". For me it returns null, so I thought that I need to name unique constraints in hbm's. But I do not know how to do it.

Also I thought that it is good strategy to try to save something and then catch for constraints exceptions as opposed to check manually if for example userId does not exist and then if not save something. Am I wrong?

Hello,
when you persist use saveOrUpdate() method, hibernate will figure out whether to update or save. In case you do not want to update, try to retrieve it first. eg:

two choices:



Its a standard behaviour in hibernate.

Thans emiakoup for trying to help. This partially solves my problem. But in general my problem is little more complicated.

Suppose we have User object which have:
firstName, lastName,
employeeId (must be unique),
policyId (must be unique),
boxNumber (must be unique).

No we create User object and trying to save it. No we have at least two options:
1. check if there is no user having such employeeId, check if there is no user with such policyId, check if there is no user with such boxNumber and then if all is ok, save User
2. save User object and catch exceptions e.g. ConstraintViolationException and from it (using getConstraintName() method) get know which constraint was violated.

The problem with option one is too many checks, too many sql queries to db. Option two is much better (expecially when constraint violation is supposed to be very rare) but... and here is my problem - I do not now how to set up constraint name in hbm's, so these name would be set in database and getConstraintName() method (or other not known by me) returns these name. I tried to catch ConstraintViolationException and it catches but getConstraintName returns null.

Personally I think that option two is better but please help me know how to get which constraint was violated.

Hello,
here is what i found, this will actually name the constraint:



try it.

How to name the constraint using Hibernate Annotations? Any clue?

Thanks in advance.

Hello With annotations (you need hibernate as JPA), you do something like the following:



and for separate column:

Hi, thanks emiakoup for trying to help. Actually, I want to know how to name the constraint using Hibernate Annotations. In your example you were able to define a constraint using Hibernate Annotation, but there is no name for it.

Hello JaVaSan,
here is something i found:

Hello emiakoup,
Thank you for the point. I didn't know about @ForeignKey annotation.
I think we can't name constraints like these:



Note that we have two constraints (nullable and unique), but there's no way to name them. Hibernate don't allow us to name them because it's not possible. Take a look at this DDL (based on MySQL database):



Note that there's no way to name the "not null" and "unique" constraints.

next post... (submitted twice

Hello JaVaSan,
raise a feature request in JIRA. Once you have the schema in place and tables generated, you can do it from MySQL side (Toad etc.,).