多对多联接表的foreignKey或inverseForeignKey

Question

I have a Spring project that uses JPA with Hibernate and MySQL and a database with three tables: Users, Roles, and join table User Roles. Could you please tell me whether I should use inverseForeignKey attribute in the inverseJoinColumn or keep it as it is (simply foreignKey)?

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

    // Class contains some other variables and methods that are irrelevant to this question

    // All annotations are from javax.persistence package
    @ManyToMany(cascade = CascadeType.ALL)
    @JoinTable(name = "user_roles", 
        joinColumns = @JoinColumn(name = "user_id", foreignKey = @ForeignKey(name = "FK_users_user_roles_user_id")), 
        inverseJoinColumns = @JoinColumn(name = "role_id", foreignKey = @ForeignKey(name = "FK_roles_user_roles_role_id")))
    private Set<Role> roles;

    }

SQL scripts for all tables:

CREATE TABLE `users` (
  `user_id` int(11) NOT NULL AUTO_INCREMENT,
  `email` varchar(255) NOT NULL,
  `username` varchar(255) NOT NULL,
  `password` varchar(255) NOT NULL,
  `points` bigint(11) NOT NULL,
  `rank` varchar(255) DEFAULT NULL,
  `registered_at` date DEFAULT NULL,
  `avatar` varchar(255) DEFAULT NULL,
  `full_name` varchar(255) DEFAULT NULL,
  `info` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`user_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `roles` (
  `role_id` int(11) NOT NULL AUTO_INCREMENT,
  `role` varchar(255) DEFAULT NULL,
  PRIMARY KEY (`role_id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

CREATE TABLE `user_roles` (
  `user_id` int(11) NOT NULL,
  `role_id` int(11) NOT NULL,
  PRIMARY KEY (`user_id`,`role_id`),
  CONSTRAINT `FK_roles_user_roles_role_id` FOREIGN KEY (`role_id`) REFERENCES `roles` (`role_id`) ON DELETE CASCADE ON UPDATE CASCADE,
  CONSTRAINT `FK_users_user_roles_user_id` FOREIGN KEY (`user_id`) REFERENCES `users` (`user_id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

Answer 1

You can simply use referencedColumnName to refer the primary key of the parent tables in join table. Your @ManyToMany mapping can be like below.

@ManyToMany(cascade = CascadeType.ALL)
@JoinTable(name = "user_roles", 
    joinColumns = @JoinColumn(name = "user_id", referencedColumnName="user_id"), 
    inverseJoinColumns = @JoinColumn(name = "role_id", referencedColumnName="role_id"))
private Set<Role> roles;

Please refer here