#OneToMany Pesist Child when creating Parent Entity - postgresql

Question

I have a OneToMany Relationship (User to EmailAddress)
Maybe I'm going about this the wrong way, My Database is empty but If I want to POST a User object and add it to the Database, along with the emailAdresses object and have the EmailAddress persisted also.
I want 2 records in the Database:
1 User and 1 EmailAddress (with a fk to User table)
Service Class
Currently what I've implemented to get this to work is this:
#Service
public class UserService {
private UserRepository userRepository;
private ModelMapper modelMapper;
public UserService(UserRepository userRepository, ModelMapper modelMapper) {
this.userRepository = userRepository;
this.modelMapper = modelMapper;
//Used for mapping List
modelMapper.getConfiguration()
.setFieldMatchingEnabled(true)
.setFieldAccessLevel(Configuration.AccessLevel.PRIVATE)
.setSourceNamingConvention(NamingConventions.JAVABEANS_MUTATOR);
}
public User createUser(UserCreateDTO userCreateDTO) {
User user = modelMapper.map(userCreateDTO, User.class);
//persist User to EmailAddress object
if(user.getEmailAddresses() != null){
user.getEmailAddresses().forEach(user::persistUser);
}
return userRepository.save(user);
}
public UserDTO getUserById(Long id) {
User found = userRepository.findById(id).get();
return modelMapper.map(found, UserDTO.class);
}
// .....
Which I have seen used in some bidirectional relationships
User Entity
#Entity
#Table(name = "Users")
#Getter #Setter #ToString #NoArgsConstructor
public class User {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "user_id", updatable = false, nullable = false)
private Long id;
private String firstName;
private String lastName;
private int age;
#OneToMany(fetch = FetchType.LAZY, mappedBy = "user", cascade = CascadeType.ALL, orphanRemoval = true)
private List<EmailAddress> emailAddresses;
Email Address Entity
#Entity
#Table(name = "Email")
#Getter #Setter #ToString #NoArgsConstructor
public class EmailAddress {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name="email_id", updatable = false, nullable = false)
private Long emailId;
private String email;
#ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.PERSIST )
#JoinColumn(name = "user_id", nullable = false)
#JsonIgnore
private User user;
Is there a better way to set up the Join relationship?
Sample POST Request
{"firstName":"Joe", "lastName":"Bloggs", "age": 30, "emailAddresses" : [ "joe-private#email.com" , "joe-work#email.com" ] }

Answer 1

I guess you need to associate this email with a user as well, not just set user to email entity.
public void persistUser(EmailAddress emailAddress) {
// set this email to the user
// if email EmailAddresses list is null you might need to init it first
this.getEmailAddresses().add(emailAddress);
emailAddress.setUser(this);
}

Answer 2

Firstly, I believe that a method persistUser should not be a part of a service layer - due to its implementation it mostly like a Domain layer method that should be implemented within a User entity class.
Secondly, since it's a POST method you shouldn't care of emails existence - you are adding a new user with a new set of emails
Closer to a question, I'd suggest you to try this:
public class UserService {
/************/
#Autowired
private UserManager userManager;
public void addUser(UserModel model) {
User user = new User(model);
List<EmailAddress> emails = model.getEmailAddresses().stream().map(EmailAddress::new).collect(Collectors.toList());
user.setEmailAddresses(emails);
userManager.saveUser(user);
}
}
and at the User add this:
public void setEmailAddresses(List<EmailAddress> emails) {
emails.forEach(item -> item.setUser(this));
this.emailAddresses = emails;
}
And don't forget to implement constructors for entities with model paremeters