Session attribute being removed when not serializable

[marten koomen]

Hi

This is a confusing problem for me that started after changing IDE from Netbeans 6.8 to 7.0.1, and after some refactoring. I have tested a lot and have managed to pin it down a bit.

The problem is that a key session attribute is removed from the session after a file is written. Through using listeners I have found the following:

1. The following version of the attribute is removed after the FileWriter is instansiated.

session.setAttribute("test", new SessionAdmin2());
...
public class SessionAdmin2 {
        SessionAdmin2() {
        }
}

but this serializable version does not get removed

session.setAttribute("test", new SessionAdmin2());
...
public class SessionAdmin2 implements Serializable{
        SessionAdmin2() {
        }
}

2. When using the non serialized version of the the above, the attribute is removed when the following code is called

      public static void writeFormletRendition2(File file, FormletStateEditable  rendition)  {
        try {
            FileWriter  fileWriter = new FileWriter(file);
            fileWriter.close();

        } catch (IOException e) {
            e.printStackTrace();
        }     

    }

but not when this code is called instead

 public static void writeFormletRendition3(File file, FormletStateEditable  rendition)  {
 
    }

perhaps it's a memory problem.

Anybody any ideas???

Thanks

Marten

Below is a stack trace on an exception thrown and caught when the attribute is removed

attributeRemoved: test : com.tuliptest.controller.SessionAdmin2@1e9a140
                session: 7269A5A814CCFB9F79E43BC7DE6FB26D
java.lang.Exception
	at com.tuliptest.campaign.SessionListener.printStackTrace(SessionListener.java:70)
	at com.tuliptest.campaign.SessionListener.attributeRemoved(SessionListener.java:37)
	at org.apache.catalina.session.StandardSession.removeAttributeInternal(StandardSession.java:1692)
	at org.apache.catalina.session.StandardSession.writeObject(StandardSession.java:1536)
	at org.apache.catalina.session.StandardSession.writeObjectData(StandardSession.java:989)
	at org.apache.catalina.session.StandardManager.doUnload(StandardManager.java:517)
	at org.apache.catalina.session.StandardManager.unload(StandardManager.java:463)
	at org.apache.catalina.session.StandardManager.stop(StandardManager.java:667)
	at org.apache.catalina.core.StandardContext.stop(StandardContext.java:4611)
	at org.apache.catalina.manager.ManagerServlet.stop(ManagerServlet.java:1327)
	at org.apache.catalina.manager.ManagerServlet.doGet(ManagerServlet.java:380)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
	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.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:558)
	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)

[William Brogden]

Since a servlet container is allowed to serialize a session any time it wants to, you should never rely on a non serializable attribute being maintained.

Bill

[marten koomen]

Thanks Bill,

I now understand that, I will change my design.

Cheers

Marten

[marten koomen]

OK, so I have changed the design so that only serializable attributes are added to the session, but I still seem to have an underlying problem with the context being destroyed; seemingly randomly.

I get the stack trace below. It seems that the reason that my non serializable attribute problem manifested now was because of some other reason, probably related to changing my IDE.

Any ideas on what this stack trace may means?

Thanks

Marten

Context Destroyed!
java.lang.Exception
	at com.tuliptest.campaign.SysContextInitialise.printStackTrace(SysContextInitialise.java:91)
	at com.tuliptest.campaign.SysContextInitialise.contextDestroyed(SysContextInitialise.java:60)
	at org.apache.catalina.core.StandardContext.listenerStop(StandardContext.java:4011)
	at org.apache.catalina.core.StandardContext.stop(StandardContext.java:4615)
	at org.apache.catalina.manager.ManagerServlet.stop(ManagerServlet.java:1327)
	at org.apache.catalina.manager.ManagerServlet.doGet(ManagerServlet.java:380)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
	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.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:558)
	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)

[marten koomen]

OK, so this was an Netbeans IDE - Subversion interaction problem.

I was writting myfiles to inside my WEB_INF folder which I can see in my IDE and is version controlled.

When I write my files to a filepath outside of the application path it all works fine. This problem only started happening when I changed to Netbeans 7.0.1.

There is nothing like problem to show you the world.

Cheers