Hi all, During my work, I use request.isRequestedSessionIdValid to check whether the session is valid before I invalidate one session, the code is like below: if (request.isRequestedSessionIdValid()){ | session.invalidate(); | } However, those codes do not always work correctly. Sometimes, there will be IllegalStateException caused by the 'session.invalidate', the stack trace is like below: anonymous wrote : java.lang.IllegalStateException: invalidate: Session already invalidated | at org.jboss.web.tomcat.service.session.ClusteredSession.invalidate(ClusteredSession.java:669) | at org.apache.catalina.session.StandardSessionFacade.invalidate(StandardSessionFacade.java:150) | . Can anybody tell me why? Thanks in advance. BTW: while doing the search across the forum, I find one post which covered the similar issue: http://www.jboss.com/index.html?module=bb&op=viewtopic&t=135699, but unfortunately, there is no reply for that post. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4183120#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...