What are differences between save and saveOrUpdate method of

ghz 9months ago ⋅ 63 views

In Hibernate, both the save() and saveOrUpdate() methods of the Session object are used to persist objects to the database. However, they differ in their behavior and usage:

  1. save() Method:

    • The save() method is used to persist a new transient object to the database.
    • If the object is in the transient state (i.e., not associated with any Hibernate session), save() inserts the object into the database and assigns it a unique identifier (primary key).
    • If the object is already persistent (i.e., associated with a Hibernate session), calling save() on it will throw an exception.
    • save() returns the identifier (primary key) of the saved object.

  2. saveOrUpdate() Method:

    • The saveOrUpdate() method is used to persist or update an object to the database, depending on its state.
    • If the object is transient (i.e., not associated with any Hibernate session) or has a null identifier (primary key), saveOrUpdate() inserts the object into the database and assigns it a unique identifier.
    • If the object is detached (i.e., previously associated with a Hibernate session but not currently managed), saveOrUpdate() reattaches it to the session and either inserts it as a new row (if it has a null identifier) or updates the existing row (if it has a non-null identifier).
    • If the object is persistent (i.e., associated with a Hibernate session), saveOrUpdate() has no effect. The object is already being tracked by the session, and changes made to it will be automatically synchronized with the database.
    • saveOrUpdate() returns void.

In summary, the main differences between save() and saveOrUpdate() are:

  • save() is used specifically for persisting new transient objects to the database, while saveOrUpdate() can be used for persisting new objects as well as updating existing objects.
  • save() always inserts a new row into the database, while saveOrUpdate() inserts a new row for transient objects and updates an existing row for detached objects.
  • save() returns the identifier (primary key) of the saved object, while saveOrUpdate() returns void.
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