如何正确使用一对多和多对一注释？

Question

Good day,

I have started my first JPA project based on a CRM application and I have some difficulties with understanding the correct usage of ManyToOne and OneToMany annotations. For instance, let's say I have two classes; these will be Account and User classes:

public class Account {

@OneToMany
private Set<User> userList = new HashSet<User>();

and

public class User {

@ManyToOne
private Account account;

How do I correctly annotate the many-to-one and one-to-many relationships? I've tried reading the docs but still I could not retrieve a correct conclusion.

Thank for your attention

Answer 1

A 'canonical' OneToMany mapping for your case, meaning meaning bidirectional, with the foreign key in the table of the many-side (the owning side) would in your case look like this:

public class Account {

@OneToMany(mappedBy="account")
private Set<User> userList = new HashSet<User>();

and

public class User {

@ManyToOne
private Account account;

The only difference to your existing code is the mappedBy attribute, to change two unidirectional relationships into a single, bidirectional relationship.