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

Question

I think I misunderstood the meaning of cascading in the context of a  ManyToOne relationship   The case   public class User        OneToMany fetch   FetchType EAGER     protected Set lt Address gt  userAddresses      public class Address        ManyToOne fetch   FetchType LAZY  cascade   CascadeType ALL     protected User addressOwner       What is the meaning of the cascade   CascadeType ALL  For example  if I delete a certain address from the database  how does the fact that I added the cascade   CascadeType ALL affect my data  the User  I guess

User · Answer

From the EJB3 0 Specification   Use of the cascade annotation element may be used to propagate the effect of an operation to associated entities  The cascade functionality is most typically used in parent-child relationships  If X is a managed entity  the remove operation causes it to become removed  The remove operation is cascaded to entities referenced by X  if the relationships from X to these other entities is annotated with the cascade REMOVE or cascade ALL annotation element value   So in a nutshell  entity relationships defined with CascadeType All will ensure that all persistence events such as persist  refresh  merge and remove that occur on the parent  will be passed to the child  Defining other CascadeType options provides the developer with a more granular level of control over how the entity association handles persistence  For example if I had an object Book that contained a List of pages and I add a page object within this list   If the  OneToMany annotation defining the association between Book and Page is marked as CascadeType All  persisting the Book would result in the Page also being persisted to the database

User · Answer

If you just want to delete the address assigned to the user and not to affect on User entity class you should try something like that    Entity public class User       OneToMany mappedBy    addressOwner   cascade   CascadeType ALL     protected Set lt Address gt  userAddresses   new HashSet lt  gt         Entity  public class Addresses       ManyToOne cascade   CascadeType REFRESH   JoinColumn name    user id      protected User addressOwner      This way you dont need to worry about using fetch in annotations  But remember when deleting the User you will also delete connected address to user object

User · Answer

The meaning of CascadeType ALL is that the persistence will propagate  cascade  all EntityManager operations  PERSIST  REMOVE  REFRESH  MERGE  DETACH  to the relating entities   It seems in your case to be a bad idea  as removing an Address would lead to removing the related User  As a user can have multiple addresses  the other addresses would become orphans  However the inverse case  annotating the User  would make sense - if an address belongs to a single user only  it is safe to propagate the removal of all addresses belonging to a user if this user is deleted    BTW  you may want to add a mappedBy  addressOwner  attribute to your User to signal to the persistence provider that the join column should be in the ADDRESS table

User · Answer

You shouldn t use CascadeType ALL on  ManyToOne since entity state transitions should propagate from parent entities to child ones  not the other way around  The  ManyToOne side is always the Child association since it maps the underlying Foreign Key column  Therefore  you should move the CascadeType ALL from the  ManyToOne association to the  OneToMany side  which should also use the mappedBy attribute since it s the most efficient one-to-many table relationship mapping

User · Answer

In JPA 2 0 if you want to delete an address if you removed it from a User entity you can add orphanRemoval true  instead of CascadeType REMOVE  to your  OneToMany   More explanation between orphanRemoval true and CascadeType REMOVE is here

User · Answer

See here for an example from the OpenJPA docs  CascadeType ALL means it will do all actions  Quote   CascadeType PERSIST  When persisting an entity  also persist the entities held in its fields  We suggest a liberal application of this cascade rule  because if the EntityManager finds a field that references a new entity during the flush  and the field does not use CascadeType PERSIST  it is an error  CascadeType REMOVE  When deleting an entity  it also deletes the entities held in this field  CascadeType REFRESH  When refreshing an entity  also refresh the entities held in this field  CascadeType MERGE  When merging entity state  also merge the entities held in this field   Sebastian

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

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