Hello,
I am using Hibernate 3.1.
My hibernate.cfg.xml is as follows :

<hibernate-configuration>
<session-factory name="foo">
<property name="hibernate.cglib.use_reflection_optimizer">true</property>
<property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
<property name="hibernate.connection.password">password</property>
<property name="hibernate.connection.url">jdbc:oracle:thin:@x.x.x.x:xxxxxxx</property>
<property name="hibernate.connection.username">xx</property>
<property name="hibernate.default_schema">xxxxxxxx</property>
<property name="hibernate.dialect">org.hibernate.dialect.Oracle9Dialect</property>
<property name="hibernate.show_sql">true</property>
<mapping resource="VsDomainWorkflowRef.hbm.xml" />
<mapping resource="VsRequestFieldT.hbm.xml" />
<mapping resource="VsSystemConfigurationT.hbm.xml" />
<mapping resource="VsBrandCountryMapT.hbm.xml" />
<mapping resource="VsDbmsResourcesRef.hbm.xml" />
<mapping resource="VsMdnsAccountT.hbm.xml" />
<mapping resource="X.hbm.xml" />
<mapping resource="VsDbmsRegLevelRef.hbm.xml" />
...... 50 more maping files

I have a layered architecture,

For each hibernate operation, a session is opened using a threadLocal logic.

Example:
public VsDnsProfile findByPrimaryKey(Long id) {
Session session = null;
VsDnsProfile record = null;
try {
session = HibernateUtil.currentSession();
record = new VsDnsProfile();
record = (VsDnsProfile) session.get(VsDnsProfile.class, id);

} catch (Exception e) {

e.printStackTrace();
} finally {
if (session != null) {
try {
HibernateUtil.closeSession();

} catch (Exception e) {
e.printStackTrace();
}
}
}

return record;
}


-------------

HibernateUtil:


public class HibernateUtil {

private static final SessionFactory sessionFactory;

static {
// Create the SessionFactory
sessionFactory = new Configuration().configure().buildSessionFactory();
}

public static final ThreadLocal session = new ThreadLocal();

public static Session currentSession() throws HibernateException {
Session s = (Session) session.get();
// Open a new Session, if this Thread has none yet
if (s == null) {
s = sessionFactory.openSession();
session.set(s);
}
return s;
}

public static void closeSession() throws HibernateException {
Session s = (Session) session.get();
session.set(null);
if (s != null)
s.close();
}
}


The log has many select statemenst which were not performed by my application : Is there some setting I need to set, is the performance getting bad with so many accesses to database.

Is the stragtegy of openeing a session and closing a session for each hibernate transcation correct ?


Thanks
Shobhana

I see nothing wrong with the way you handle session but i use an Assembler(J2EEpattern) to gather all calls(database/hibernate) into one Session.

A more common technique to do this is to begin the transation in a servlet filter and commit/rollback transaction and close session it at the end of the filter.

I dont think you should open/close commit/begin at every call, but maybe i misundestood your question.

see http://www.hibernate.org/43.html
this explains a lot of what im trying to say.
My difference to this example is that i do a session.close() in a finally clause that this example does not (dont know why though).

/robert

What exactly do you mean when you say you have a session for each "Hibernate operation"? A natural usage pattern is to have a session per "business transaction". Creating and closing a session for something as low-level as a "findByPrimaryKey" operation would not fit that pattern at all. It would result in a lot of unecessary session overhead. But your statement about too many database accesses doesn't necessarily correlate with your session usage. The session would help only in those cases where the session cache would contain persisitent objects that are used throughout your business transaction. If you keep closing and opening sessions, you won't be able to use the cache, and they will have to be retrieved from the database each time.

Thanks for the reply.

What I meant is that I have DAO layer, which has all the data access operations like(save,load, findByprimaryKey, etc ..)

For each of this operations I do the follwoing things :

Example to load a object with a primary key
------------------------------------------------------------------>
public VsDnsProfile findByPrimaryKey(Long id) {
Session session = null;
VsDnsProfile record = null;
try {
session = HibernateUtil.currentSession();
record = new VsDnsProfile();
record = (VsDnsProfile) session.get(VsDnsProfile.class, id);
} catch (Exception e) {
LogDbmsInfo("Exception VsDnsProfileDAOImpl");
e.printStackTrace();
} finally {
if (session != null) {
try {
HibernateUtil.closeSession();

} catch (Exception e) {
e.printStackTrace();
}
}
}

return record;
}

------------------------------------------------------------->



Thanks
Shobhana

Your session logic should definitely be in a layer above the DAO layer.