I'm using Hibernate 3.

I have to retrieve a persistence instance and update it. When i try retrieving the same record and update it again, it throws an exception "NonUniqueObject"

Then I tried using a session.merge(). it updates the record, but I have a problem retrieving the same record again. it retreives the previous value before the update. however if i refresh the page I get the updated value. (but this is also inconsistent...sometimes i get the updated value while retrieving for the first time and get the wrong values later on)
Sometimes I even get deadlocks while updating the record.

I'm providing here the codes for updating the records.


public static boolean updateDept( Department dept, DepartmentPK pk )
{

try
{
HibernateUtil.beginTransaction( Constants.UDB_DATABASE );
Session session = HibernateUtil.getSession( Constants.UDB_DATABASE );

Department deptInSession = (Department) session.get( Department.class, pk );

copyProperties(dept, deptInSession); // this uses the BeanUtils to copy the properties from dept to deptInSession.
session.merge( deptInSession);

HibernateUtil.commitTransaction( );

session.refresh( dept );
return true;

} catch( HibernateException e )
{

HibernateUtil.rollbackTransaction( );
paslog.error( e.getMessage( ) );
return false;

}

}


pls suggest me on what I can do.
Thanx in advance.
Anand.

Basically merge will do automatically all you try to do manually. As its name suggests it merges state of the given object with a state of persistent object. So, in code it looks like this ( provided that the given department object has proper key):

public static boolean updateDept( Department dept )
{

try
{
HibernateUtil.beginTransaction( Constants.UDB_DATABASE );
Session session = HibernateUtil.getSession( Constants.UDB_DATABASE );

session.merge(dept);

HibernateUtil.commitTransaction( );
return true;

}

Hi,
Thanks for the reply.

If I try using the session.merge() alone , it gives a "not-null property references a null or transient value:" exception.
So I explicitly copied the dept properties to the deptInSession properties.

this helped me to resolve the problem and update works fine now. But I get a deadlock when I try to retrieve the rows again for another update.

So I'm not sure whether I'm using the session.merge() properly.
pls reply if u have more suggestions.
Thanks,
Anand.

Please post code of that attempt.

Hi,



This is the code I use to retrieve records.

public static ArrayList getFluClinicFamily( String enteredBy )
{

ArrayList fluFamilyList = new ArrayList( );
try
{
Session session = HibernateUtil.getSession( Constants.UDB_DATABASE );
StringBuffer sql = new StringBuffer( "from FluClinic as fluClinic " );
sql.append( "where fluClinic.enteredBy = :enteredBy " );
sql.append( "order by fluClinic.enterTimeStamp desc " );

Query query = session.createQuery( sql.toString( ) );
query.setParameter( "enteredBy", enteredBy );

fluFamilyList = (ArrayList) query.list( );

} catch( HibernateException e )
{
paslog.error( e );
return null;
}

return fluFamilyList;

}


I select certain records for update using the following code.

public static ArrayList getFluClinicByTimeStamp( String enterTimeStamp, String enteredBy )
{

ArrayList fluClinicByTimeStampList = new ArrayList( );

try
{

Session session = HibernateUtil.getSession( Constants.UDB_DATABASE );
StringBuffer sql = new StringBuffer( "from FluClinic as fluClinic " );
sql.append( "where fluClinic.enterTimeStamp = :enterTimeStamp " );
sql.append( "and fluClinic.enteredBy = :enteredBy " );
sql.append( "and fluClinic.transactionStatus not in ('D','U','C') " );

Query query = session.createQuery( sql.toString( ) );
query.setParameter( "enterTimeStamp", enterTimeStamp );
query.setParameter( "enteredBy", enteredBy );

fluClinicByTimeStampList = (ArrayList) query.list( );

} catch( HibernateException e )
{
paslog.error( e );
return null;
}

return fluClinicByTimeStampList;

}


And this the actual code I use for updating the records.

public static boolean updateFluClinic( FluClinic fluClinic, FluClinicPK pk )
{

try
{
HibernateUtil.beginTransaction( Constants.UDB_DATABASE );
Session session = HibernateUtil.getSession( Constants.UDB_DATABASE );

FluClinic flu = (FluClinic) session.get( FluClinic.class, pk );

combineProperties(fluClinic, flu);// this copies the fluClinic properties to flu properties.
session.merge( flu);

HibernateUtil.commitTransaction( );

return true;

} catch( HibernateException e )
{

HibernateUtil.rollbackTransaction( );
paslog.error( e.getMessage( ) );
return false;

}

}



I get a deadlock after one round trip. What could be the reasons? this is a part of the application and the Mapping works fine for the main application.

Thanks,
Nithya.

The problem is that (if it worked) you'd have both fluClinic and flu being persistent objects representing the same row in the database. Hibernate doesn't allow that, but apparently you've found a nifty way around the usual NonUniqueException.

You could go the other way: copy fluClinic properties to flu, because flu is the version you loaded from the database. Then just session.update(flu).

When this sort of thing happened to me, I used session().replicate(fluClinic, ReplicationMode.OVERWRITE). With this, you don't have to re-attach fluClinic, and you don't have to get flu from the DB first. So long as fluClinic's id is correct, it will work.