i don't know why that is happening...
org.apache.catalina.session.StandardSession writeObject
WARNUNG: Cannot serialize session attribute SessionBean1 for session FE3C10ABDF8FDE020A4A4879560D980B
java.io.NotSerializableException: oracle.jdbc.driver.T4CConnection
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1156)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1509)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1474)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1392)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1150)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:326)
at org.apache.catalina.session.StandardSession.writeObject(StandardSession.java:1462)
at org.apache.catalina.session.StandardSession.writeObjectData(StandardSession.java:938)
at org.apache.catalina.session.StandardManager.doUnload(StandardManager.java:516)
at org.apache.catalina.session.StandardManager.unload(StandardManager.java:462)
at org.apache.catalina.session.StandardManager.stop(StandardManager.java:666)
at org.apache.catalina.core.StandardContext.stop(StandardContext.java:4345)
at org.apache.catalina.manager.ManagerServlet.stop(ManagerServlet.java:1226)
at org.apache.catalina.manager.ManagerServlet.doGet(ManagerServlet.java:370)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:689)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:174)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:524)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664)
at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80)
at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684)
at java.lang.Thread.run(Thread.java:619)