class Person
{
String login;//unique
String email //unique
}
I would like to insert into database new Person, but before that i would like to check if in database are already objects with the same email or login. I don't want to execute 3 statements in my java code:
1. check if there is Person with the same login
2. check if there is Person with the same email
3. insert new person

If i wouldn't use Hibernate i would write stored procedure smothing like this:
CREATE PROCEDURE..

IF EXISTS(SELECT * FROM Persons WHERE login=@login)
return 1;
IF EXISTS(SELECT * FROM Persons WHERE email=@email)
return 2;

INSERT INTO Persons VALUES ...;
return 0;

So i would execute i stored procedure and received information wheter Person was added and if not - why

My question is whether in hibernate is some way to recevie information about problems during session.save(). If i simply use session.save() and in database is already person with the same email or login I will only recevie ContraintViolationHibernate without information wich contriaint was violated.

Your Dialect needs to implement an override of getViolatedConstraintNameExtracter() since the default just returns null.
i.e. each dialect needs to know how to parse the constraint name out of the SQLException message string.

There is an example of this in the Oracle9Dialect implementation that ships with Hibernate.