Relationship with Enumerated Type in Java

Question

I'm trying to create a many-to-many relationship between two types of which one is an Enumerated type. Lets say the first model is User and the second model is Role. A user can have many roles and a role can belong to many users.

I'd like to be able to write simple code like:

if (user.getRoles().contains(Role.ADMIN)) {
  //do something
}

Does anyone know if this is possible? I've seen that there is an @Enumerated Hibernate annotation but this doesn't look to be of use to me.

I've currently implemented a solution by created a model for a link table but this is very messy. Any help much appreciated.

-gearoid

UPDATE: Can someone specify how to persist an EnumSet on a model? The info above still stands, I wish to create a ManyToMany relationship with an Enumerated Type.

Answer 1

Have you had a look at the EnumSet class? This can store multiple Enum instances in a collection you can call contains() on

Answer 2

We usually create subclasses EnumUserType and then specify this class in the mapping file.

Answer 3

I think I have found a good solution to the problem. If I keep my Enumerated Type as something simple such as:

public enum Role implements Serializable{

    USER, MODERATOR, ADMIN;

}

And then on my User model I create a Set of Roles with the @CollectionOfElements so it looks something like this:

  @CollectionOfElements(fetch = FetchType.EAGER)
  public Set<Role> getRoles() {
   return roles;
  }

  public void setRoles(Set<Role> roles) {
   this.roles = roles;
  }

Hibernate seems to create a table for this relationship (called user_roles) which works as I'd like (A regular manyToMany relationship).

Hope this helps someone.

-gearoid.