many to many mapping exception in EJB3

[mravikrish]

Hello EveryOne,
i've mapped many2many between user and skill tables ,when it is uni-directional works fine but the problem occurs when i made it to bi-directional. i've written many2many mapping in user class

The following exception is thrown when i try to insert record.

Caused by: java.sql.BatchUpdateException: ORA-01400: cannot insert NULL into ("SYSTEM"."CUSER_SKILL"."CUSER_USERID")

CUSER_USERID(column) is getting created automatically in join table.


thanks in advance.

[wolfgangknauf]

Hi,

bi-directional mappings are a bit tricky: you always have to update BOTH sides of the mapping.

So, if you want to map a Skill to an User, this will NOT work:

user.getSkills().add ( mySkill);
entityManager.merge(user);

You will have to do something like this:

myUser.getSkills().add ( mySkill);
mySkill.getUsers().add (myUser);
entityManager.merge(myUser);

Hope this helps

Wolfgang