You only need to dispose of the session when you no longer want the session. It's perfectly valid to keep reusing the session as long as you want, inserting, removing and calling fire all rules as many times as you want. If you do reuse the session you just need to be careful that previous iterations of the loop don't have undesirable results on subsequent executions - eg if your rules insert control facts and you don't tidy them up. So in the code below you should just move the dispose outside the loop after you have done all the iterations. Thomas I have a quesion about StatefulKnowledgeSession.dispose(). Can continue to use the session instance ofter call dispose() method. I write a test code to test it and it is works fine. and it is almot 10 time fast than not call dispose(). Why??? But When I use Jboss Enterprise BRMS to run this test case. It is throw a NullPointException when call dispose() at the second time. Why???? for (int i = 0; i < 100; i++) { FactHandle handle = session.insert(messageList.get(i));// session.fireAllRules(); session.retract(handle); session.dispose(); } ************************************************************************************** This message is confidential and intended only for the addressee. If you have received this message in error, please immediately notify the postmaster(a)nds.com and delete it from your system as well as any copies. The content of e-mails as well as traffic data may be monitored by NDS for employment and security purposes. To protect the environment please do not print this e-mail unless necessary. NDS Limited. Registered Office: One London Road, Staines, Middlesex, TW18 4EX, United Kingdom. A company registered in England and Wales. Registered no. 3080780. VAT no. GB 603 8808 40-00 **************************************************************************************

It's probably because dispose unregisters from various listeners and clears up some housekeeping resources, timers etc. It's possible your rules are simple enough that they don't need any of this and so not calling the listeners saves a significant amount of time - particularly if your test case is overly trivial . Whether it keeps working in any future versions I wouldn't want to guarantee you, dispose may start nulling out fields etc that would break future calls to the methods. Thomas ************************************************************************************** This message is confidential and intended only for the addressee. If you have received this message in error, please immediately notify the postmaster(a)nds.com and delete it from your system as well as any copies. The content of e-mails as well as traffic data may be monitored by NDS for employment and security purposes. To protect the environment please do not print this e-mail unless necessary. NDS Limited. Registered Office: One London Road, Staines, Middlesex, TW18 4EX, United Kingdom. A company registered in England and Wales. Registered no. 3080780. VAT no. GB 603 8808 40-00 **************************************************************************************

I think you are right, I change my test case. Just call dispose() at the first time. and the performance is the same as call it every time. What ever the dispose method do, It is really really impact the performance...10 times for (int i = 0; i < 100; i++) { FactHandle handle = session.insert(messageList.get(i));// session.fireAllRules(); session.retract(handle); if(i== 0){ session.dispose(); } } -- View this message in context: http://drools.46999.n3.nabble.com/StatefulKnowledgeSession-dispose-tp3440... Sent from the Drools: User forum mailing list archive at Nabble.com.