Hibernate中的单向一对多映射会生成冗余更新

Question

I have defined two classes, Parent and Child. The parent can have a list of children.

@Entity
public class Parent {
    @Id
    @GeneratedValue(...)
    @SequenceGenerator(...)
    private long id;

    @OneToMany(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinColumn(name = "parent_id", referencedColumnName = "id", nullable = false)
    private List<Child> children;

    public Parent() {
        children = new ArrayList<Child>();
    }

    public void addChild(Child child) { children.add(child); }
}

@Entity
public class Child {
    @Id
    @GeneratedValue(...)
    @SequenceGenerator(...)
    private long id;

    // The "Child" table in the db also has a not-null "parent_id" column.
}

If I add a bunch of children to the list and persist the parent everything works as expected: Hibernate gets the sequence values, stores the parent and then stores all the children.

However, after doing all this, it updates all the children, setting the "parent_id" to the value it was already set to in the insert!

The generated SQL looks like this:

insert into PARENT (id) values (1)
insert into CHILD (parent_id, id) values (1, 1)
insert into CHILD (parent_id, id) values (1, 2)
insert into CHILD (parent_id, id) values (1, 3)
update CHILD set parent_id = 1 WHERE id = 1
update CHILD set parent_id = 1 WHERE id = 2
update CHILD set parent_id = 1 WHERE id = 3

If I make this association bidirectional it works fine, but then I need a reference to the parent in my child class and that's something I want to avoid.

The repository is a Spring Data JPA repository:

public interface ParentRepository extends PagingAndSortingRepository<Parent, Long> {}

The (simplified) code that creates and saves the objects:

Parent parent = new Parent();
parent.addChild(new Child());
parent.addChild(new Child());
repo.save(parent);

Any suggestions?

Answer 1

你有没有尝试过：

@JoinColumn(name = "parent_id", referencedColumnName = "id", nullable = false, insertable=false, updatable=false)