[jboss-user] [Beginner's Corner] - Re: ManyToMany problem

Wolfgang Knauf do-not-reply at jboss.com
Thu Oct 29 11:53:24 EDT 2009


I assume that you want to use EJB3/JPA for creating your entities?

In this case, you don't need a role_function entity, and the server will autogenerate the database table for you. The entity "Role" will have a list of "Functions", and the "Function" will have a list of "Role", both connected by annotations.


  | @Entity
  | public class Role implements Serializable
  | {
  |    @ManyToMany (mappedBy="roles")
  |    public List<Function> functions;
  | }
  | @Entity
  | public class Function implements Serializable
  | {
  |    @ManyToMany ()
  |    public List<Role> roles;
  | }

Then, your code can access the functions of a role by "myRole.functions.get(x);". The rest is the job of the server and you don't have to care much about it.

Of course, there is quite a bit more to keep in mind. First of all, the two fields should have a getter and setter. More detailed information can be found here: http://www.jboss.org/community/wiki/EJB3relationships

Hope this helps


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