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@PreUpdate doesn’t save parent object when it’s updated

I have two entities with relation one to many. Parent can have several Child entity instances. I added a field to the parent that stores the date of children modifications(childrenLastModifiedDate). To maintain that, I added method:

@PrePersist
@PreUpdate
@PreRemove
private void handle() {
    parent.setChildrenLastModifiedDate(now());
}

Here is the problem. It’s not always invoke when the child is saved. Locally(mac os), it works as expected, all three types of changes are tracked and saved to the parent entity. However, on the server(linux) it only works for:

  • @PrePersist
  • @PreRemove

Even though, PreUpdate is invoked, the changes are not saved. I have even tried to add a direct repository call to save the parent. The result is the same. Nothing is saved on update, but saved on remove or persist. I tried to make this change in additional transaction and it worked, but it’s too resource consuming. Also, I can see that someone had very similar experience:

JPA/Hibernate preUpdate doesn’t update parent object

However, there is nothing on how to handle the problem itself. The question is: is there a way to guarantee that using of this annotations will always work and perform additional updates of dependent entities? If it’s not, what is the best way to handle such logic? The update is required on each change to children. Even if it is saved by cascade.

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Answer

I got the same problem. I fixed it by using Hibernate Interceptor.

First, you have to declare some base method in the base entity class that allow us to find the parent of an entity, an a method to chaining update your desired fields.

public abstract class BaseEntity {
    public Optional<BaseEntity> getParent() {
        // subclass should override this method to return the parent entity
        return Optional.empty();
    }
    public void updateChain() { 
        // update your desired fields
        ...
        this.getParent().ifPresent(p -> p.updateChain());
    }
}

Then you can use following Hibernate interceptor to force update all parents of the dirty entities.

public class EntityChainForceUpdateHibernateInterceptor extends EmptyInterceptor {

    @Override
    public void preFlush(Iterator entities) {
        entities.forEachRemaining(e -> {
            if (BaseEntity.class.isAssignableFrom(e.getClass())) {
                BaseEntity b = (BaseEntity) e;
                b.getParent().ifPresent(p -> p.updateChain());
            }
        });
    }
}

To register this interceptor with Spring, just add following line to application.properties

spring.jpa.properties.hibernate.ejb.interceptor=com.your.package.EntityChainForceUpdateHibernateInterceptor

And this is an example of how to override the getParent().

@MappedSuperclass
public abstract class BaseEntity {

    @Column(name = "last_updated_at")
    private Instant lastUpdatedAt;

    public Optional<BaseEntity> getParent() {
        return Optional.empty();
    }
    public void updateChain() {
        this.lastUpdatedAt = Instant.now();
        this.getParent().ifPresent(p -> p.updateChain());
    }
}

@Entity
public class ParentEntity extends BaseEntity {
    @Id
    @Column(name = "id")
    private String id;

    @Column(name = "something")
    private String somethingToUpdateWhenChildSaved;

    @Override
    public void updateChain() {
        this.somethingToUpdateWhenChildSaved = "anything";
        super.updateChain();
    }
}

@Entity
public class ChildEntity extends BaseEntity {

    @ManyToOne
    @JoinColumn(name = "parent_id", referencedColumnName = "id")
    private ParentEntity parent;

    @Override
    public Optional<BaseEntity> getParent() {
        return Optional.of(this.parent);
    }
}

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