[rules-users] persisting a stateful session

[chris]

Hi there,

I apologize in advance if this seems like a trivial question, but I can't
seem to figure out what the issue is. i am trying to serialize a stateful
session to file in a very simple test program. So I am using the code from
Michael Bali's book to define a stateful drools session:

// 
package sertest;

import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;
import java.io.Serializable;
import org.drools.KnowledgeBase;
import org.drools.common.DroolsObjectInputStream;
import org.drools.common.DroolsObjectOutputStream;
import org.drools.logger.KnowledgeRuntimeLogger;
import org.drools.logger.KnowledgeRuntimeLoggerFactory;
import org.drools.marshalling.Marshaller;
import org.drools.marshalling.MarshallerFactory;
import org.drools.marshalling.ObjectMarshallingStrategy;
import org.drools.marshalling.ObjectMarshallingStrategyAcceptor;
import org.drools.runtime.StatefulKnowledgeSession;
import org.drools.runtime.rule.FactHandle;

/**
 *
 * 
 */
public class DroolsService implements Serializable
{

    private static final long serialVersionUID = 3L;
    private transient KnowledgeBase knowledgeBase;
    private transient StatefulKnowledgeSession statefulSession;


    public DroolsService( KnowledgeBase knowledgeBase )
    {
        this.knowledgeBase = knowledgeBase;
        statefulSession = createKnowledgeSession();
    }

    private StatefulKnowledgeSession createKnowledgeSession()
    {
        StatefulKnowledgeSession session =
knowledgeBase.newStatefulKnowledgeSession();
        return session;
    }

    public void insertOrUpdate( Object fact )
    {
        if( fact == null )
        {
            return;
        }

        FactHandle factHandle = statefulSession.getFactHandle( fact );

        if( factHandle == null )
        {
            statefulSession.insert( fact );
        }
        else
        {
            statefulSession.update( factHandle, fact );
        }
    }

    public void executeRules()
    {
        KnowledgeRuntimeLogger logger = 
        KnowledgeRuntimeLoggerFactory.newFileLogger(statefulSession,
"accessPackageLog");
        statefulSession.fireAllRules();
        logger.close();
    }

    public void terminate()
    {
        statefulSession.dispose();
    }

    private void writeObject( ObjectOutputStream out ) throws IOException
    {
        out.defaultWriteObject();
        DroolsObjectOutputStream droolsOut = new DroolsObjectOutputStream(
(OutputStream) out );
        droolsOut.writeObject( knowledgeBase );
        Marshaller marshaller = createSerializableMarshaller( knowledgeBase
);
        marshaller.marshall( droolsOut, statefulSession );
    }

    private void readObject( ObjectInputStream in ) throws IOException,
ClassNotFoundException
    {
        in.defaultReadObject();
        DroolsObjectInputStream droolsIn = new DroolsObjectInputStream(
(InputStream) in );
        this.knowledgeBase = (KnowledgeBase) droolsIn.readObject();
        Marshaller marshaller = createSerializableMarshaller( knowledgeBase
);
        statefulSession = marshaller.unmarshall( droolsIn );
    }

    private Marshaller createSerializableMarshaller( KnowledgeBase
knowledgeBase )
    {
        ObjectMarshallingStrategyAcceptor acceptor =
MarshallerFactory.newClassFilterAcceptor( 
                new String[]
                {
                    "*.*"
                } );

        ObjectMarshallingStrategy strategy =
MarshallerFactory.newSerializeMarshallingStrategy( acceptor );
        Marshaller marshaller = MarshallerFactory.newMarshaller(
knowledgeBase, 
                 new ObjectMarshallingStrategy[]
                {
                    strategy
                } );
        return marshaller;
    }
}
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////


In the test client I just do the following:

//
KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();
DroolsService droolsService = new DroolsService( kbase );

File file = new File("out.ser");

ObjectOutputStream oos = new ObjectOutputStream(
     new FileOutputStream(file));
oos.writeObject(droolsService);
oos.close();
///////////////////////////////////////////////////////////////////

The code then trows an exception:
Exception in thread "main" java.io.IOException: Write error
        at java.io.FileOutputStream.writeBytes(Native Method)
        at java.io.FileOutputStream.write(FileOutputStream.java:260)
        at
java.io.ObjectOutputStream$BlockDataOutputStream.drain(ObjectOutputStream.java:1838)
        at
java.io.ObjectOutputStream$BlockDataOutputStream.setBlockDataMode(ObjectOutputStream.java:1747)
        at
java.io.ObjectOutputStream.writeNonProxyDesc(ObjectOutputStream.java:1249)
        at
java.io.ObjectOutputStream.writeClassDesc(ObjectOutputStream.java:1203)
        at
java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1387)
        at
java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1150)
        at
java.io.ObjectOutputStream.writeFatalException(ObjectOutputStream.java:1538)
        at
java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:329)
        at sertest.Main.main(Main.java:30)


If I take out the last 2 lines in the writeObject method above (i.e. don't
use a marshaller to write out the stateful session) then there is no
exception.

Any ideas what might be causing this??

Kind regards,
Chris

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