CODEWITHSUNDEEP
javaspringspring-bootspring-data-jpaspring-data
Minato Namikaze
Minato Namikaze

Reputation: 606

Spring one-to-many always empty

I have 2 entities A & B. Both are related via new entity AB.

public class A {
    // other fields
    @OneToOne(mappedBy = "a")
    private AB ab;
}

public class B {
    // other fields
    @OneToOne(mappedBy = "b")
    private AB ab;
}

public class AB{
    // more fields
    @ManyToOne
    @JoinColumn(name = "a_id")
    private A a;

    @ManyToOne
    @JoinColumn(name = "b_id")
    private B b;
}

Now above code works, but when I try to add a relationship directly from A to B, my results are always empty.

public class A {
    // other fields
    @OneToOne(mappedBy = "a")
    private AB ab;

        @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
        private Set<B> b;
}

Upvotes: 0

Views: 406

Answers (1)

Selindek
Selindek

Reputation: 3423

The problem is that you use @OneToOne from one side and @ManyToOne from the other side.

You should use @OneToMany in the class A and B. What is quite logical: If multiple AB can be connected to A, then there should be a collection of ABs in class A.

And after you change those annotations, you can immediately see that the relation between A and B is @ManyToMany.

Upvotes: 1

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