Cannot unmarshall large session file: InvalidProtocolBufferException

Run the followoing java program. Tip: -Xmx4G MarshallUnmarshall.java package org.drools_25; import java.io.*; import org.drools.*; import org.drools.builder.*; import org.drools.io.*; import org.drools.marshalling.*; import org.drools.runtime.StatefulKnowledgeSession; public class MarshallUnmarshall { static String rules = " package org.drools_25 " + "" + "rule Populate_many " + "" + "when " + " o : Integer (); " + "then " + " for ( int i=0; i<5000000; i++) {" + " insert(\" Fact: \ " + i);" + " }" + "end" ; public static void main( String [] args) throws Exception { StatefulKnowledgeSession kb = largeKb(); File f = marshallKb(kb); kb.dispose(); // Expect exception here unmarshallKb(f); } private static void unmarshallKb(File f) throws Exception { System .out.println( "Reading from " + f.getName()); FileInputStream in = new FileInputStream(f); Marshaller marshaller = MarshallerFactory .newMarshaller(KnowledgeBaseFactory.newKnowledgeBase()); marshaller.unmarshall(in); } private static File marshallKb(StatefulKnowledgeSession kb) throws Exception { File kbfile = new File( "out.bin" ); System .out.println( "Writing to " + kbfile.getName() + ". This will take a while ..." ); FileOutputStream out = new FileOutputStream(kbfile); Marshaller marshaller = MarshallerFactory.newMarshaller(kb.getKnowledgeBase()); marshaller.marshall(out, kb); return kbfile; } private static StatefulKnowledgeSession largeKb() { Resource myResource = ResourceFactory .newReaderResource( new StringReader(rules)); KnowledgeBuilder kbuilder = KnowledgeBuilderFactory .newKnowledgeBuilder(); kbuilder.add(myResource, ResourceType.DRL); KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase(); kbase.addKnowledgePackages(kbuilder.getKnowledgePackages()); StatefulKnowledgeSession session = kbase.newStatefulKnowledgeSession(); session.insert( new Integer (1)); System .out.println( "Filling up knowledge base." ); session.fireAllRules(); System .out.println( "Done. Factcount = " + session.getFactCount()); return session; } }