Hibernate version: 3

We are looking to convert an existing Application to Java and are looking to use Hibernate as the persistency layer. This application is a thick client app and will be based on J2SE. The application is BIG with large numbers of domain objects.

If I understand correctly, Hibernate takes a copy of an objects contents when it is read from the session. It then uses this information to determine of an object has changed when the session is flushed. We are worried that in our application this could a) take up a large amount of memory and b) cause performance problems when a flush occurs. If a thousand objects are read and only one is updated, Hibernate will check all objects for changes - this could take some time. Is it possible to configure that behaviour so that objects are not copied on load, but when say session.update(anObject) is executed ?

Could someone please help me with this request ?

Hi,

your concerns may be right.
When using the session cache you should have a
concept of "unit of work". Perhaps you can read:

http://www.hibernate.org/42.html

The easiest way is to write a small
test application.
Controlling the session cache can be done
in several ways like session.clear or evict.
Or using the stateless session.

Hope this helps a bit.

Hi,
Thanks for the help. I have taken a look at StatelessSession, but unforchinatly this session does not handle proxies or collections !!!!
Anyother ideas ?
I have a test application that I am using.
Regards
Ian

I want to utialize the session cache, I just do not want the session to think that every object that is being read "could" be updated.

Is there a way to work with two sessions, say a readonly session for handling the main work of the application, and a second session, where objects could be "updated" in and could be used to control object changes ?

Is it possible to configure a session to be readonly ?

I have been able to create a read only session by creating a second set of mapping files, each one having mutable="false" within the class definitions.

I then create two sessions, one on the read only mapping and one on the read/write mappings. I then read the objects form the read only session. I get caching, but no "deepCopy" is created. I then "update" the object in the second (read/write) session and then modify it. When I flush the read/write session, the object is updated in the DB... GREAT.

However I have a few questions.
1) Creating two sets of mapping files means I have LOTS of mapping files to maintain. Also using two sets also means that the start up time of Hibernate is almost doubled. Is it possible to just use just one set ?

2) Is this a "good" use og hibernate ? Am I just forcing hibernate to do something it really does not want to do ?

3) Is there a better way of creating a read only session ?

Thanks
Ian

i just try answering your first questions based on my kowleage of hibernate.
hope a bit help for you .:)
1)you can use just one set of mapping files.likes below:
<class name="cim.core.Naming" table="NAMING" >
<id>...........</id>
<property >......</property>
<class>
<class name="cim.core.BaseVoltage" dynamic-update="true" table="BASEVOLTAGE">
<id>...........</id>
<property >......</property>
</class>

that's a lot of code ... why don't you keep the same SINGLE set of mapping files and do the following:

1.) build Configuration
2.) build sesionFactory 1
3.) loop through Configuration.getCLassMappings().getProperties() , setting all properties to non-mutable

or ...

transform the same set of mapping files with a little XSLT.

4.) build sessionFactory 2