get vs load

UltimoAmore · **Joined:** Tue Jan 27, 2004 8:33 am **Posts:** 29

Sorry if this has been already answered, but I couldn't find
anything searching on the forums (looking for "get" and "load" is too
generic...).
I don't understand the difference between loading an object using
Session.load and using Session.get.

What does it mean "assuming that the instance exists" in the "load" docs?
What happens when the instance doesn't exist?
Is there a performance difference between Session.get and Session.load?

Thank you in advance.

Myk · **Joined:** Sun Jan 04, 2004 2:46 pm **Posts:** 147

The main difference between load and get is that get will always hit the database and return the requested object ( or null if it's not there ) whereas load ( if you are using a lazy/proxied class ) will not hit the database on the load call. All it does it make a proxy class, fills in the primary key and leaves it. The database is only accessed when you request a property of that object which will lead to unexpected errors if the object doesn't exist. Therefore only use load for objects that definately do exist, if you're not sure or want to check, use get.

Cheers.

Myk.

UltimoAmore · **Joined:** Tue Jan 27, 2004 8:33 am **Posts:** 29

Thank you. Only a thing:
what happens when the instance doesn't exist (using load and without lazy/proxy)?

michael · **Posted:** Tue Feb 17, 2004 7:10 am

You get an Exception of course.

max · **Posted:** Tue Feb 17, 2004 12:21 pm

....but first when you access a non-id attribute on the object....!

michael · **Posted:** Tue Feb 17, 2004 12:23 pm

without lazy/proxy you get an exception immediately ;)

max · **Posted:** Tue Feb 17, 2004 12:40 pm

of course....busy day ...only reading postings 77% ;)

stolley · **Posted:** Tue Feb 17, 2004 8:21 pm

Myk wrote:

The main difference between load and get is that get will always hit the database and return the requested object

Will get() hit the DB if the object has already been loaded in that Session?

michael · **Posted:** Tue Feb 17, 2004 8:28 pm

hispanic · **Joined:** Fri Mar 19, 2004 2:04 pm **Posts:** 1

Q:

Quote:

Will get() hit the DB if the object has already been loaded in that Session?

A:

Quote:

No.

This seems dangerous (and annoying) to me. Basically, the behavior of the get() method varies per object based on whether or not it has already been resolved via load(). This matters most when the object has been deleted. But I don't see how the behavior of the get() method can be improved. Tell me whether or not using the following code in my Hibernate facade seems like a good practice:

Code:

public Object get(Class clazz, Serializable id)
{
     Object entity = session.get(clazz, id);
     if (entity != null && isProxy(entity))
     {
          evict(entity);
          entity = get(clazz, id);
     }
     return entity;
}

This way, get always returns an object or null, never a proxy, especially for an object that has been deleted.

I appreciate the feedback.

gavin · **Posted:** Thu Mar 25, 2004 8:41 pm

It is not at all dangerous or annoying.

If you want to hit the DB, use Session.get(clazz, id, LockMode.READ)