How to Perform Cascading Deletes on a JPA Entity Collection

What is the process to implement cascading deletes for collections within a JPA entity?

@Entity
public class Parent {
    @Id
    private Long id;

    @OneToMany(mappedBy = "parent", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Child> children;
}

@Entity
public class Child {
    @Id
    private Long id;

    @ManyToOne
    @JoinColumn(name = "parent_id")
    private Parent parent;
}

Cascading deletes in JPA (Java Persistence API) allow for the automatic removal of related entities when a parent entity is deleted. This feature is particularly useful in managing relationships between entities, ensuring database integrity and reducing orphan records.

// Code Snippet to demonstrate cascading delete implementation
@Entity
public class Parent {
    @Id
    private Long id;

    @OneToMany(mappedBy = "parent", cascade = CascadeType.ALL, orphanRemoval = true)
    private List<Child> children;

    // Method to remove a child
    public void removeChild(Child child) {
        children.remove(child);
        child.setParent(null);
    }
}

@Entity
public class Child {
    @Id
    private Long id;

    @ManyToOne
    @JoinColumn(name = "parent_id")
    private Parent parent;
}

Causes

• The parent entity is deleted and there are still corresponding child entities without the cascade option set.
• You are not using the correct cascade type for cascading deletes (e.g., CascadeType.Remove).
• The orphanRemoval flag is not set, causing child entities to persist even after the parent is deleted.

Solutions

• Set the cascade type to CascadeType.ALL or at least CascadeType.REMOVE on the relationship mapping.
• Enable orphanRemoval=true to ensure that any removed child entity is also deleted from the database.
• Properly manage bidirectional relationships by synchronizing the parent and child relationships.

Mistake: Forgetting to use orphanRemoval, which can lead to orphan child entities.

Solution: Always set orphanRemoval=true in the OneToMany annotation when you want to delete child entities.

Mistake: Not synchronizing both sides of a bidirectional relationship, which may result in inconsistencies.

Solution: Ensure that when you link or unlink child entities to a parent, you also properly update the parent's collection.