Jpa OneToMany not deleting child

java

entity-relationships

jpa-configuration

cascade-deletion

byNikita Barsukov·Dec 28, 2024

Here's the quick fix for removing child entities in a JPA @OneToMany relationship: set orphanRemoval = true and tie it up with either CascadeType.REMOVE or CascadeType.ALL. Don't forget to refresh the parent-side relationship by disassociating the child entity from the parent's collection.

@Entity
public class Parent {
    @OneToMany(mappedBy = "parent", cascade = CascadeType.ALL, orphanRemoval = true)
    private Set<Child> children;

    public void removeChild(Child child) {
        children.remove(child); // child is kicked out
        child.setParent(null); // Effective way to avoid "I want my mommy" exceptions
    }
}

To trigger the child's departure from the database, simply call parent.removeChild(childEntity) within a transaction.

The story behind cascade behavior

When mapping objects in JPA, it's critical to slice through object modeling's complexity like a hot knife through butter, particularly where composition and aggregation play their roles. Composition suggests an all-or-nothing approach, where child entities can't exist without their parent, hence the need for a cascade delete.

Tailoring `@OneToMany` for seamless deletion

Why go for a bespoke solution?

Switch orphanRemoval = true for no-child-left-behind policy.
Tailor a bi-directional suit; both @OneToMany and @ManyToOne will be the perfect fit, empowering JPA to manage relationships like a pro.
For ultimate control, choose CascadeType.PERSIST, CascadeType.MERGE, and CascadeType.DELETE as weapons. CascadeType.ALL may sound like a Swiss Army knife but can lead to unintended casualties.

Harness vendor-specific horsepower

Ride on your JPA provider's strengths:

Hibernate squatters can apply @org.hibernate.annotations.OnDelete with the OnDeleteAction.CASCADE strategy, or use Hibernate' secret stash—cascade delete_orphan to clean up leftovers.
EclipseLink explorers, consider "private ownership" as your treasure map to similar cascade delete functionality.

A practical guide to foolproof deletion

When bidding farewell to entities, remember:

Do a full dress rehearsal, particularly with Ajax-powered delete operations. Practice until you make it perfect.
Understand that a little freedom (like child.setParent(null)) won't erase the child entity unless backed by orphanRemoval.
Keep searching the mirror: is your JPA provider version supporting orphan removal? If using Hibernate, it should be no less than 3.5.0-Beta-2.
Understand the underlying database operations resulting from JPA's entity relationships.

Considerations to ponder

Is orphanRemoval really needed or are you inviting trouble to your party unnecessarily?
Be pensive with CascadeType.ALL. You might sweep away entities that were meant to stick around.
Set your transaction boundaries correctly. Treat them as your safety net to catch relational changes and commit them properly.

explain-codes / Java / Jpa OneToMany not deleting child

Linked

What is the meaning of the CascadeType.ALL for a @ManyToOne JPA association



Can someone explain mappedBy in JPA and Hibernate?



Hibernate - A collection with cascade=”all-delete-orphan” was no longer referenced by the owning entity instance



Jpa or JDBC, how are they different?



How to fix the Hibernate "object references an unsaved transient instance - save the transient instance before flushing" error

