Spring Data JPA multiple one to many relations from primary key as a foreign key

Question

I'm working on tinder-like Spring Boot and Angular web app, but stuck at making relationship in JPA (I've done relations in postgreSQL database in pgAdmin) I tried @OneToMany, @JoinColumns and other methods, but can't figure out how to make it and if making relationship like this is even possible, because I hadn't found example like this on any site (including Stackoverflow of course)

When one person swipe right another person application will insert into Swipes

• id: id

• decision: yes/no

• swipeFrom: id of profile who sent like (profiles.id)

• swipeTo: id of profile who gets like (profiles.id)

• timestamp: timestamp

AND IN EVERY OTHER TABLES IT WILL WORK LIKE ABOVE

Is relations like this possible? If not, what should I do? Maybe just left it like it's and just delete Matches, Swipes etc. manually in method when parent is deleted?

Answer 1

Although I don't know what you've tried, but it is possible. If you want bidirectional mapping, you would have:

@Entity
@Table(name = "profiles")
public class Profile {

    // other fields

    @OneToMany(mappedBy = "sender", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Message> sentMessages = new ArrayList<>();

    @OneToMany(mappedBy = "receiver", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Message> receivedMessages = new ArrayList<>();

    // other collections for swipes, matches and timers
}

@Entity
@Table(name = "messages")
public class Message {

    // other fields

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "message_from")
    private Profile sender;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "message_to")
    private Profile receiver;
}

The same applies for other tables (swipes, matches, timers). You use @JoinColumn to specify which foreign key you want to map to which field.

If you want unidirectional mapping or something else, I encourage you to check Vlad Mihalcea 's article The best way to map a @OneToMany relationship with JPA and Hibernate .

---

Note : You'll need to use Criteria API (or some other approach) if you want to fetch Profile with sent and received Messages. If you would try something like:

@Query("from Profile p join fetch p.sentMessages join fetch p.receivedMessages where p.id = :id")
Optional<Profile> findProfileByIdFetchSendAndReceivedMessages(int id);

or

@Override
@EntityGraph(attributePaths = { "sentMessages", "receivedMessages" })
Optional<Profile> findById(int id);

you would get MultipleBagFetchException .

Since there are many great articles on this topic, I will not go into details now. For example, you can check another Vlad Mihalcea 's article The best way to fix the Hibernate MultipleBagFetchException if you ran into this issue.