SpringBoot + JPA @ManyToMany 操作要点

SpringBoot + JPA @ManyToMany 要点

这里主要时记录下此种方法的注意事项。

对应的Entity的建立。此处注意不可使用lombok @Data 注解。使用@Setter 、@Getter注解。主要原因时要自己覆写hash() equals(),toString() 方法。这样添加和删除的时候不会出现异常。否则出现循环的引用，不能删除或stackOver；

User

@Setter
@Getter
@Entity
public class User {


    @Id
    @GenericGenerator(name="jpauuid",strategy = "org.hibernate.id.UUIDGenerator")
    @GeneratedValue(generator = "jpauuid")
    @Column(length = 32,nullable = false)
    private String  id;

    @Column(length = 30)
    private String username;

    @ManyToMany(cascade = CascadeType.REFRESH,mappedBy = "users")
    @JsonBackReference  //防止无限引用
    private Set<Role> roles;


    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        User user = (User) o;
        return id.equals(user.id) &&
                username.equals(user.username) &&
                roles.equals(user.roles);
    }

    @Override
    public int hashCode() {
        return Objects.hash(id, username, roles);
    }

    @Override
    public String toString() {
        return "User{" +
                "id='" + id + '\'' +
                ", username='" + username + '\'' +
                ", roles=" + roles +
                '}';
    }
}

Role

@Setter
@Getter
@Entity
public class Role {

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

    @Column(length = 30)
    private String  name;


    @ManyToMany(cascade = CascadeType.REFRESH)
    @JoinTable(name = "user_role",joinColumns = @JoinColumn(name = "role_id"),inverseJoinColumns = @JoinColumn(name="user_id"))
    private Set<User>  users;


    public void addUser(User user){
        this.users.add(user);
    }


    public void removeUser(User user){
        this.users.remove(user);
    }

}

Junit的测试 注意@transaction的注解一定要加上。

   /**
     * 添加角色
     */
    @Test
    public void addRole(){
        Role role = new Role();
        role.setName("系统管理员");
        roleRepository.save(role);
    }

    /**
     * 添加用户
     */
    @Test
    public void addUser() {
        User user = new User();
        user.setUsername("test1");
        userRepostitory.save(user);
    }

    /**
     *
     * 通过关系维护方添加角色和用户的关系
     */
    @Test
    @Transactional
    public void  addUserRole(){
        User user = userRepostitory.findByUsername("test1");
        Role role = roleRepository.getOne(1);
        role.addUser(user);
        roleRepository.saveAndFlush(role);
    }

    /**
     *
     * 删除对应的关联数据
     */
    @Test
    @Transactional
    public void removeRoleUser(){
        User user = userRepostitory.findByUsername("test1");
        Role role = roleRepository.getOne(1);
        role.removeUser(user);
        roleRepository.saveAndFlush(role);
    }