Gary thanks for replying, but the thread wasn't helpful.
Thanks a lot Demian, it was a perfect example for me. Through the example I was able to run the application as a desktop applicaton, and it worked perfectly fine and persisted to my postgres database. But when I decided to run the same application as a web application with tomcat 6.0 for deployment, then I get this exception at this line:
StatefulKnowledgeSession ksession = JPAKnowledgeService.newStatefulKnowledgeSession(kbase, null, env);
AM org.drools.persistence.jta.JtaTransactionManager rollback
WARNING: Unable to rollback transaction
java.lang.NullPointerException
at org.drools.persistence.jta.JtaTransactionManager.rollback(JtaTransactionManager.java:181)
at org.drools.persistence.SingleSessionCommandService.<init>(SingleSessionCommandService.java:131)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at org.drools.persistence.jpa.KnowledgeStoreServiceImpl.buildCommanService(KnowledgeStoreServiceImpl.java:116)
at org.drools.persistence.jpa.KnowledgeStoreServiceImpl.newStatefulKnowledgeSession(KnowledgeStoreServiceImpl.java:54)
at org.drools.persistence.jpa.JPAKnowledgeService.newStatefulKnowledgeSession(JPAKnowledgeService.java:109)
at org.apache.jsp.index_jsp._jspService(index_jsp.java:169)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:377)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:619)