JPA One To Many Relationship Persistence Bug

Question

I've got a really weird problem with a bi-directional relationship in jpa (hibernate implementation). A User is based in one Region, and a Region can contain many Users.

So...relationship is as follows:

Region object:

@OneToMany(mappedBy = "region", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
public Set<User> getUsers() {
  return users;
}
public void setUsers(Set<User> users) {
  this.users = users;
}

User object:

@ManyToOne(cascade = {CascadeType.PERSIST, CascadeType.MERGE}, fetch = FetchType.EAGER)
@JoinColumn(name = "region_fk")
public Region getRegion() {
  return region;
}
public void setRegion(Region region) {
  this.region = region;
}

So, the relationship as you can see above is Lazy on the region side, ie, I don't want the region to eager load all the users. Therefore, I have the following code within my DAO layer to add a user to an existing user to an existing region object...

public User setRegionForUser(String username, Long regionId){
  Region r = (Region) this.get(Region.class, regionId);
  User u = (User) this.get(User.class, username);
  u.setRegion(r);
  Set<User> users = r.getUsers();
  users.add(u);
  System.out.println("The number of users in the set is: "+users.size());
  r.setUsers(users);
  this.update(r);
  return (User)this.update(u);
}

The problem is, when I run a little unit test to add 5 users to my region object, I see that the region.getUsers() set always stays stuck at 1 object...somehow the set isn't getting added to.

My unit test code is as follows:

public void setUp(){
  System.out.println("calling setup method");
  Region r = (Region)ManagerFactory.getCountryAndRegionManager().get(Region.class, Long.valueOf("2"));
  for(int i = 0; i<loop; i++){
    User u = new User();
    u.setUsername("username_"+i);
    ManagerFactory.getUserManager().update(u);
    ManagerFactory.getUserManager().setRegionForUser("username_"+i, Long.valueOf("2"));
  }
}

public void tearDown(){
  System.out.println("calling teardown method");
  for(int i = 0; i<loop; i++){
    ManagerFactory.getUserManager().deleteUser("username_"+i);
  }
}

public void testGetUsersForRegion(){
  Set<User> totalUsers = ManagerFactory.getCountryAndRegionManager().getUsersInRegion(Long.valueOf("2"));
  System.out.println("Expecting 5, got: "+totalUsers.size());
  this.assertEquals(5, totalUsers.size());
}

So the test keeps failing saying there is only 1 user instead of the expected 5. Any ideas what I'm doing wrong?

thanks very much, Brian

Answer 1

What is the implementation for update(r) ? Are you remembering to commit?

Answer 2

What is the implementation of hashcode and equald in User? Maybe all your users are considered the same in the Set so only one gets saved.