Question

I am reading about HibernateTemplate class in Spring3.

Here i saw two methods update and saveOrUpdate , i read it from the documentation such as

• update

Update the given persistent instance, associating it with the current Hibernate Session.

Here what is meaning of “associating it with the current Hibernate Session”?

• saveOrUpdate

Save or update the given persistent instance, according to its id (matching the configured “unsaved-value”?). Associates the instance with the current Hibernate Session.

Here what is meaning of “according to its id (matching the configured “unsaved-value”?). Associates the instance with the current Hibernate Session” ?

Please help me

Thanks in advance

Answer 1

Simple – If the object with the same ID exists in the DB , it updates it else if the ID (primary key) is null, it saves it as a new value – Hence saveOrUpdate – depending on whether it’s a value existing in DB or a new value.

The ID match happens by matching your pojo ID in the hbm under the tag with the column specified .

saveOrUpdate() does the following:

if the object is already persistent in this session, do nothing

if another object associated with the session has the same identifier, throw an exception

if the object has no identifier property, save() it

if the object's identifier has the value assigned to a newly instantiated object, save() it

if the object is versioned by a <version> or <timestamp>, and the version property value is the same value assigned to a newly instantiated object, save() it

otherwise update() the object 

From here

Hope this helps.