Hi,

Using, JDK 1.5.07
hsqldb_1_8_0_4
hibernate-3.2.CR2.jar
hibernate-annotations-3.2.0.CR1.jar

I have been trying to create a manytomany association between two entities, UserImpl and RoleImpl. A user has many roles and a role has many users.


User is the owner and defines the following

@ManyToMany(
targetEntity = RoleImpl.class)
@JoinTable(
name = "users_roles",
joinColumns = {@JoinColumn(name = "USER_ID")},
inverseJoinColumns = {@JoinColumn(name = "ROLE_ID")}
)
public Set<Role> getRoles()
{
return roles;
}


On the other side i have...

@ManyToMany(
mappedBy = "roles",
targetEntity = UserImpl.class,
)
public Set<User> getUsers()
{
return this.users;
}


Now if i add roles (which are already persisted) to a user and persist the user with getHibernateTemplate().saveOrUpdate(user);

Then i get what expect, which is that a user is created in the USER table and an entry appears in USERS_ROLES mapping the user to its associated roles.

My problem occurs when i try and do exactly the same but the other way around....

I add a user (again already persisted) to a role and then persist the role with getHibernateTemplate().saveOrUpdate(role) but this time no entry appears in USERS_ROLES - which is what i expected.

Am i misunderstanding the concept of bidirectional manytomany or have i got a problem here?

Yep.

Read about it in Hibernate Core docs.
- http://www.hibernate.org/hib_docs/v3/re ... irectional

I think you need maintain both ends of the relationship in Java code. That means whenever you add roles to a user, you need to add the user object to role objects' users set at the same time. So does adding users to a role.