I started by wanting to get rid of an ERole enum type that my TA used to enumerate some roles that users can have. It looks like this:

public enum ERole {
    CUSTOMER,
    MANAGER,
    ADMIN
}

Because we’re learning spring boot, the way that my TA persisted these Roles in a database was like this:

@Entity
@RequiredArgsConstructor
@AllArgsConstructor
@Builder
@Data
public class Role {
    @Id
    @GeneratedValue( strategy = GenerationType.IDENTITY )
    private Integer id;

    @Enumerated( EnumType.STRING )
    @Column( length = 20 )
    private ERole name;
}

The “role” table is needed because a user can have multiple roles. A many-to-many relationship between the “user” and “role” tables is used.

@Entity
@Table ( uniqueConstraints = { @UniqueConstraint ( columnNames = { "username", "email" } ) } )
@RequiredArgsConstructor
@AllArgsConstructor
@Builder
@Data
public class User {

    @Id
    @GeneratedValue ( strategy = GenerationType.IDENTITY )
    private Long id;

    @Column ( nullable = false, length = 20 )
    private String username;

    @Column ( nullable = false, length = 50 )
    private String email;

    @Column ( nullable = false, length = 120 )
    private String password;

    @ManyToMany ( fetch = FetchType.LAZY )
    @JoinTable ( name = "user_roles",
            joinColumns = @JoinColumn ( name = "user_id" ),
            inverseJoinColumns = @JoinColumn ( name = "role_id" ) )
    private Set <Role> roles = new HashSet <> ( );
}

My goals are the following:

1. Have just one Role enum/class where I can define my Role types
2. Have a “role” table be automatically created
3. Have these Role types be automatically inserted into the “role” table with an automatically generated and unique ID
4. Be able to create a JpaRepository for my Role enum/class

So far I’ve managed to come up with the following:

@Entity
public enum MyRole {
    CUSTOMER,
    MANAGER,
    ADMIN;

    @Id
    @GeneratedValue ( strategy = GenerationType.IDENTITY )
    private Integer id;
}

and MyRoleRepository, which looks like this:

public interface MyRoleRepository extends JpaRepository <MyRole, Integer> {
}

But I am getting this error:

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'myRoleRepository' defined in org.example.springskeleton.user.MyRoleRepository defined in @EnableJpaRepositories declared on JpaRepositoriesRegistrar.EnableJpaRepositoriesConfiguration: Unable to make field private final java.lang.String java.lang.Enum.name accessible: module java.base does not "opens java.lang" to unnamed module @4988d8b8

From what I’ve searched through documentation (@Entity, @Target, ElementType), I understand that @Entity can be used with enum types, according to its @Target annotation, but so far I have not found any examples of how that is intended to be done.

In essence, I think I have two questions:

1. Is there a better way of doing what my TA was trying to do?
2. If so, is my idea of having an enum Entity a better way/even possible?

This is my first SO question, so I’m sorry if I’ve done anything incorrectly. Thanks for the help!