唯一约束 - 密钥已存在于多对多中

Question

I have the classic many-to-many relationship between my users and their roles. It saves the first user correctly, but then when I try to insert the second user it gives me an unique key violation with (role_id)=(56) already exist...

I already tried many variations of fetching types. I am using Spring crud repositories.

My user:

@ManyToMany
@JoinTable(
        name = "user_role",
        joinColumns = @JoinColumn(name = "userId"),
        inverseJoinColumns = @JoinColumn(name = "roleId")
)
private Set<Role> roles;

public void addRole(Role role) {
    if (roles == null) {
        this.roles = new HashSet<>();
    }
    this.roles.add(role);
    role.getUsers().add(this);
}

public void removeRole(Role role) {
    this.roles.remove(role);
    role.getUsers().remove(this);
}

My roles:

@ManyToMany(mappedBy = "roles", fetch = FetchType.EAGER)
Set<User> users;

public Role(Roles role) {
    this.role = role.getRole();
    this.users = new HashSet<>();
}

My database populating code:

Role userRole = roleService.createIfNotExist(Roles.ROLE_USER);

//Role userRole = new Role(Roles.ROLE_USER);
user.addRole(userRole);

//roleRepository.save(userRole);
User result = userRepository.save(user);

If I create a new user role with new Role etc as shown in the commented out code everything works fine but I get duplicate roles saved to the data base.

Answer 1

您可以使用merge而不是persist，因为如果实体存在，它将更新它，否则插入它。