[hibernate-issues] [Hibernate-JIRA] Commented: (HHH-5858) Cannot load entities with Clob or Lob properties into stateless sessions

[Ralf Huthmann (JIRA)]

    [ https://hibernate.onjira.com/browse/HHH-5858?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=46230#comment-46230 ] 

Ralf Huthmann commented on HHH-5858:
------------------------------------

Sorry it took me so long to come back to this issue. The code shown below is in use for reading CLOBs with a stateless session and i have not encountered any issues. Please perform additional tests for your usecase. To use my replacement-class, i construct a stateless session this way:
{code}
Connection con = session.connection();
SessionFactory sf = session.getSessionFactory();
StatelessSessionWithLobImpl sls = new StatelessSessionWithLobImpl(con, (SessionFactoryImpl) sf);
{code}
Finally, this is the replacement for StatelessSessionImpl: 
{code}
package org.hibernate.impl;

import org.apache.log4j.Logger;
import org.hibernate.Session;
import org.hibernate.StatelessSession;
import org.hibernate.engine.jdbc.LobCreationContext;
import org.hibernate.exception.JDBCExceptionHelper;

import java.sql.Connection;
import java.sql.SQLException;

/**
 * Replacement for StatelessSessionImpl implementing LobCreationContext,
 * this enables the use of LOBs with a stateless session.
 * The execute-method in this class was copied from SessionImpl.
 * @see http://opensource.atlassian.com/projects/hibernate/browse/HHH-5858
 */
public class StatelessSessionWithLobImpl 
extends StatelessSessionImpl 
implements LobCreationContext
{

	private static final long serialVersionUID = 6444431664782394430L;
	private static final Logger LOGGER = Logger.getLogger(StatelessSessionWithLobImpl.class);

	public StatelessSessionWithLobImpl(Connection connection,
			SessionFactoryImpl factory) {
		super(connection, factory);
	}

	@Override
	public Object execute(Callback callback) {
		Object result;
		Connection connection = super.connection();
		boolean success = false;
		try {
			result = callback.executeOnConnection( connection );
			success = true;
		}
		catch ( SQLException e ) {
			throw JDBCExceptionHelper.convert(
					getFactory().getSQLExceptionConverter(),
					e,
					"Error creating contextual LOB : " + e.getMessage()
			);
		}
		finally {
			afterOperation(success);
		}
		
		try {
			connection.close();
		}
		catch (SQLException e) {
			LOGGER.error("Kann man nichts machen", e);
		}
		return result;
	}

}
{code}

> Cannot load entities with Clob or Lob properties into stateless sessions
> ------------------------------------------------------------------------
>
>                 Key: HHH-5858
>                 URL: https://hibernate.onjira.com/browse/HHH-5858
>             Project: Hibernate ORM
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 3.5.1
>            Reporter: James Roper
>
> I have a an entity with a Clob property:
> {code:java}
> @Lob
> private Clob clobProperty;
> {code}
> When I try and load it in a stateless session, I get:
> {noformat}
> Exception in thread "main" java.lang.ClassCastException: org.hibernate.impl.StatelessSessionImpl cannot be cast to org.hibernate.engine.jdbc.LobCreationContext
> 	at org.hibernate.Hibernate.getLobCreator(Hibernate.java:420)
> 	at org.hibernate.type.ClobType.nullSafeGet(ClobType.java:114)
> 	at org.hibernate.type.AbstractType.hydrate(AbstractType.java:105)
> 	at org.hibernate.persister.entity.AbstractEntityPersister.hydrate(AbstractEntityPersister.java:2267)
> 	at org.hibernate.loader.Loader.loadFromResultSet(Loader.java:1423)
> 	at org.hibernate.loader.Loader.instanceNotYetLoaded(Loader.java:1351)
> 	at org.hibernate.loader.Loader.getRow(Loader.java:1251)
> 	at org.hibernate.loader.Loader.getRowFromResultSet(Loader.java:619)
> 	at org.hibernate.loader.Loader.loadSingleRow(Loader.java:307)
> 	at org.hibernate.impl.ScrollableResultsImpl.prepareCurrentRow(ScrollableResultsImpl.java:254)
> 	at org.hibernate.impl.ScrollableResultsImpl.next(ScrollableResultsImpl.java:123)
> {noformat}
> If Lobs in stateless sessions isn't supported, then at very least an error message to that effect should be thrown and the docs should be updated to reflect this, but I don't see why that should be the case, especially considering that both Lobs and stateless session both serve very similar purposes, they are for use when dealing with large datasets that may not fit in memory, and so could well be used together.

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