Ufdjrw

Being new to hibernate/jpa i am facing difficulty on how to model the nested entities correctly, my requirment,
user -> have many roles -> each role have many permissions

Each permission for a role needs to be persisted as separate row in table.
And, need to have separate tables for users and theirs roles; again each role of a user need to be persisted as a separate row in table.
I wrote the below; but this is not allowing me to create new users with already defined roles...

@Entity
@Table(name = "users")
public class User implements Serializable 

 @Id
 @GeneratedValue(generator = "UUID")
 @GenericGenerator(name = "UUID",strategy = "org.hibernate.id.UUIDGenerator")
 public UUID id;

 @Column(name = "username")
 public String name;

 @Column(name = "password")
 public String password;

 @OneToMany(cascade = CascadeType.ALL, mappedBy="user")
 @LazyCollection(LazyCollectionOption.FALSE)
 public List<UserRole> roles;


@Entity
@Table(name = "user_roles")
public class UserRole implements Serializable 

 @Id
 @GeneratedValue(generator = "UUID")
 @GenericGenerator(name = "UUID",strategy = "org.hibernate.id.UUIDGenerator" )
 public UUID id;

 @ManyToOne
 @JoinColumn(name="username", nullable=false, referencedColumnName = "username")
 public User user;

 @Column(name = "role_name")
 public String roleName;

 @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.PERSIST, CascadeType.MERGE, CascadeType.REFRESH)
 @JoinColumn(name = "role_name", referencedColumnName = "role_name")
 public List<RolePermission> permissions;



@Entity
@Table(name = "roles_permissions")
public class RolePermission implements Serializable 

 @Id
 @Column(name = "role_name")
 public String roleName;

 @Id
 @Column(name = "permission")
 public String permission;

Get the below error,

2019-03-06 21:25:22.643 ERROR 48896 --- [nio-8090-exec-3]
o.h.engine.jdbc.spi.SqlExceptionHelper : ERROR: duplicate key value
violates unique constraint "uk_40fvvy071dnqy9tywk6ei7f5r" Detail:
Key (role_name)=(owner) already exists.

Got it working after correctly modelling UserRole, below is my new entity class for UserRole,

@Entity
@Table(name = "user_roles")
public class UserRole implements Serializable 

 @Id
 @GeneratedValue(generator = "UUID")
 @GenericGenerator(
 name = "UUID",
 strategy = "org.hibernate.id.UUIDGenerator"
 )
 public UUID id;

 @ManyToOne
 @JoinColumn(name="username", nullable=false, referencedColumnName = "username")
 public User user;

 @Column(name = "role_name")
 public String roleName;

 @ManyToMany
 @JoinTable(name = "roles_permissions",joinColumns = @JoinColumn(name = "role_name"))
 public List<RolePermission> permissions;