How to achieve #OneToOne User and role? - jpa

Question

I have the following tables:
+-----------------------------------+
| user |
+------------------------------------
| id | username | role_id |
+----+-------------+----------------+
| 1 | user1 | 1 |
+----+-------------+----------------+
+-----------------------------------+
| role |
+------------------------------------
| role_id | role_name |
+-----------------+-----------------+
| 1 | GUEST |
+-----------------+-----------------+
| 2 | USER |
+-----------------+-----------------+
Each user have 1 role. Fields looks like this:
User.java
#OneToOne(cascade=CascadeType.ALL)
#JoinColumn(name="ROLE_ID")
private Role role;
Role.java
#Id
#GeneratedValue
#Column(name = "ROLE_ID", unique = true, nullable = false)
private int id;
The Role table will already be populated with only 2 roles. When I try to add a new user, a new record gets saved inside Role table. This is not the behavior I'm seeking. I don't want values to be written to Role table (unless maybe the the value being added doesn't exist in the table).
Any idea how to achieve this properly? Pretty sure this is simple, but I'm new to JPA.
edit: Code to add user
user = new User("JoDoe",new Role("USER"));
user = repository.save(user);
So as pointed out by the comments, it's because I'm creating a new Role every time. Can anybody point out the proper flow please? Should I first retrieve a Role from the db via RoleDao for example, and then assign that object to the new user? Or is there any other way that I'm missing?

Answer 1

First of all, since several users can have the same role, you don't have a OneToOne, but a ManyToOne.
Second, if you create a new Role, without even assigning it an ID, and create a User with that new Role, since the association has cascade = ALL, JPA will indeed create persist this new Role. How is it supposed to know that what you actually want to do is find the role which has the same name in database and assign that role to the new User?
That's what you must do. Assuming you have the ID of the role of the new User, what you need is
Role existingRole = em.getReference(roldId);
User user = new Role(existingRole);
em.persist(user);