Friday, September 14, 2012

Difference between save vs persist and saveOrUpdate in Hibernate

Save vs saveOrUpdate vs persist in Hibernate
What is difference between save and saveOrUpdate or Difference between save and persist are common interview question in any Hibernate interview, much like Difference between get and load method in Hibernate. Hibernate Session class provides couple of ways to save object into database by methods like save, saveOrUpdate and persist.  You can use either save(),  saveOrUpdate() or persist() based upon your requirement for persisting object into Database. Along with Spring framework Interview questions, Hibernate questions are also quite popular on J2EE interviews because of its status as leading ORM. It’s good to prepare some questions from Hibernate before appearing in any J2EE interviews. One of them is Difference between save , saveOrUpdate and persist, which we will see in this Hibernate article.


Difference between save and saveOrUpdate in Hibernate
Save vs SaveOrUpdate vs Persist method in HibernateMain difference between save and saveOrUpdate method is that save() generates a new identifier and INSERT record into database while saveOrUpdate can either INSERT or UPDATE based upon existence of record. Clearly saveOrUpdate is more flexible in terms of use but it involves an extra processing to find out whether record already exists in table or not. In summary  save() method saves records into database by INSERT SQL query, Generates a new identifier and return the Serializable identifier back. On the other hand  saveOrUpdate() method either INSERT or UPDATE based upon existence of object in database. If persistence object already exists in database then UPDATE SQL will execute and if there is no corresponding object in database than INSERT will run.


Difference between save and persist method in Hibernate

In last section we saw What are difference between save and saveOrUpdate and now we will see Difference on save vs persist method.

1)First difference between save and persist is there return type. Similar to save method persist also INSERT records into database but return type of persist is void while return type of save is Serializable object.  

2) Another difference between persist and save is that both methods make a transient instance persistent. However, persist() method doesn't guarantee that the identifier value will be assigned to the persistent instance immediately, the assignment might happen at flush time.

3) One more thing which differentiate persist and save method in Hibernate is that is there behavior on outside of transaction boundaries. persist() method guarantees that it will not execute an INSERT statement if it is called outside of transaction boundaries. save() method does not guarantee the same, it returns an identifier, and if an INSERT has to be executed to get the identifier (e.g. "identity" generator), this INSERT happens immediately, no matter if you are inside or outside of a transaction.

4) Fourth difference between save and persist method in Hibernate is related to previous difference on save vs persist. Because of its above behavior of persist method outside transaction boundary, its useful in long-running conversations with an extended Session context. On the other hand save method is not good in a long-running conversation with an extended Session context.

These were some differences between save, saveOrUpdate and persist method of Hibernate. All three method are related to saving Object into database but there behavior are quite different. Knowledge of save, persist and saveOrUpdate not only helps to decide better use of Hibernate API but also help you to do well in Hibernate interviews.

Other Java tutorials you may like

3 comments :

Mahendra Kumar Kushwah said...

Thanks this very helpful..........

Anonymous said...

Please elabrate the 3 & 4 points.. from the description unable to synchronize the real concept of it.

tibi said...

is persist faster than save? not needing to retrieve the created id ??

Post a Comment