JPA unidirectional many-to-one and cascading delete

Question

Say I have a unidirectional  ManyToOne relationship like the following    Entity public class Parent implements Serializable         Id      GeneratedValue     private long id      Entity public class Child implements Serializable         Id      GeneratedValue     private long id        ManyToOne      JoinColumn     private Parent parent        If I have a parent P and children C1   Cn referencing back to P  is there a clean and pretty way in JPA to automatically remove the children C1   Cn when P is removed  i e  entityManager remove P      What I m looking for is a functionality similar to ON DELETE CASCADE in SQL

User · Answer

I have seen in unidirectional  ManytoOne  delete don t work as expected  When parent is deleted  ideally child should also  be deleted   but only parent is deleted and  child is NOT deleted and is left as orphan  Technology used are Spring Boot Spring Data JPA Hibernate  Sprint Boot    2 1 2 RELEASE  Spring Data JPA Hibernate is used to delete row  eg  parentRepository delete parent   ParentRepository extends standard CRUD repository as shown below ParentRepository extends CrudRepository lt T  ID gt   Following are my entity class   Entity name      child     public class Child          Id      GeneratedValue     private long id        ManyToOne  fetch   FetchType LAZY  optional   false       JoinColumn name      parent id   nullable   false       OnDelete action   OnDeleteAction CASCADE      private Parent parent      Entity name      parent     public class Parent         Id      GeneratedValue     private long id        Column nullable   false  length   50      private String firstName

User · Answer

Cascade org hibernate annotations CascadeType DELETE ORPHAN   Given annotation worked for me  Can have a try  For Example  -       public class Parent               Id              GeneratedValue strategy GenerationType AUTO               Column name  cct id               private Integer cct id               OneToMany cascade CascadeType REMOVE  fetch FetchType EAGER mappedBy  clinicalCareTeam   orphanRemoval true               Cascade org hibernate annotations CascadeType DELETE ORPHAN              private List lt Child gt  childs                        public class Child               ManyToOne fetch FetchType EAGER               JoinColumn name  cct id               private Parent parent

User · Answer

Relationships in JPA are always unidirectional  unless you associate the parent with the child in both directions  Cascading REMOVE operations from the parent to the child will require a relation from the parent to the child  not just the opposite    You ll therefore need to do this    Either  change the unidirectional  ManyToOne relationship to a bi-directional  ManyToOne  or a unidirectional  OneToMany  You can then cascade REMOVE operations so that EntityManager remove will remove the parent and the children  You can also specify orphanRemoval as true  to delete any orphaned children when the child entity in the parent collection is set to null  i e  remove the child when it is not present in any parent s collection  Or  specify the foreign key constraint in the child table as ON DELETE CASCADE  You ll need to invoke EntityManager clear   after calling EntityManager remove parent  as the persistence context needs to be refreshed - the child entities are not supposed to exist in the persistence context after they ve been deleted in the database

User · Answer

If you are using hibernate as your JPA provider you can use the annotation  OnDelete  This annotation will add to the relation the trigger ON DELETE CASCADE  which delegates the deletion of the children to the database  Example  public class Parent                Id         private long id       public class Child                     Id         private long id              ManyToOne          OnDelete action   OnDeleteAction CASCADE          private Parent parent           With this solution a unidirectional relationship from the child to the parent is enough to automatically remove all children  This solution does not need any listeners etc  Also a JPQL query like DELETE FROM Parent WHERE id   1 will remove the children

User · Answer

Use this way to delete only one side        ManyToOne cascade CascadeType PERSIST  fetch   FetchType LAZY       JoinColumn name    qid        JoinColumn name    qid   referencedColumnName    qid   foreignKey    ForeignKey name    qid    nullable   false          JsonIgnore      JsonBackReference     private QueueGroup queueGroup

User · Answer

Create a bi-directional relationship  like this    Entity public class Parent implements Serializable         Id      GeneratedValue     private long id        OneToMany mappedBy    parent   cascade   CascadeType REMOVE      private Set lt Child gt  children

User · Answer

You don t need to use bi-directional association instead of your code  you have just to add CascaType Remove as a property to ManyToOne annotation  then use  OnDelete action   OnDeleteAction CASCADE   it s works fine for me

[java] JPA: unidirectional many-to-one and cascading delete

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