What is cascading in Hibernate?

Question

What is cascading in Hibernate ? There is a cascade attribute I have seen in the map tag. What is it meant for?

Like what does cascade = all mean? There are other attributes I read like
cascade="none|save-update|delete|all-delete-orphan|delete-orphan".

Answer 1

Cascading is about persistence actions involving one object propagating to other objects via an association. Cascading can apply to a variety of Hibernate actions, and it is typically transitive. The "cascade=..." attribute of the annotation that defines the association says what actions should cascade for that association.

Cascade = "all" means to apply all primary cascade types. As of Hibernate 5.3, these types are:

• "delete" / "remove",
• "detach" / "evict",
• "merge",
• "lock",
• "persist",
• "refresh",
• "replicate",
• "save_update" / "update"

(Some of those cascade type names are old and/or deprecated.)

There are three more compound types:

• "all_delete_orphan" - means the same as "all" plus enabling the deletion of entities that are orphaned by the cascading.
• "delete_orphan" - means "delete" plus orphan deletion.
• "none" - means no cascading.

Answer 2

Cascading is Hibernate's way of using transitive persistence model. Transitive persistence is a technique that allows you to propagate persistence to transient (object not yet saved in database) and detached sub-graphs (child objects) automatically. For example, a newly created child object of already persistent parent object should automatically become persistent without a call to save() or persist() methods.

Cascading in Hibernate has many options like save-update, persist, merge, delete etc. Cascade='all' is a way to apply all cascading options.