java.lang.IllegalArgumentException: setAttribute: Non-serializable attribute

Question

Hi,

I have inherited some code and am getting an error when I try to run it. The error is below:

10:08:32,093 ERROR [MyServlet]:260 - Servlet.service() for servlet MyServlet threw exception
java.lang.IllegalArgumentException: setAttribute: Non-serializable attribute
at org.apache.catalina.session.StandardSession.setAttribute(StandardSession.java:1270)
at org.apache.catalina.session.StandardSession.setAttribute(StandardSession.java:1248)
at org.apache.catalina.session.StandardSessionFacade.setAttribute(StandardSessionFacade.java:130)
at uk.co.my.servlet.MyServlet.doPost(MyServlet.java:121)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:647)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at com.my.ddi.security.SecurityContextServletFilter.doFilter(SecurityContextServletFilter.java:55)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:215)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:172)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:433)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:174)
at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:835)
at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:640)
at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1286)
at java.lang.Thread.run(Unknown Source)

I imagine that the main problem is where it is hitting my code at uk.co.my.servlet.MyServlet.doPost(MyServlet.java:172). Line 121 of MyServlet is session.setAttribute("LISTENER", myListener);

This myListener object is from the following class:

public class myListener {
    static Log log = LogFactory.getLog(TerminationListener.class.getName());
    private boolean shouldCancel = false;

How would I go about getting rid of this error? Would I need to use the transient keyword?

Answer 1

If you want an instance of myListener to be placed in a session, you need to make it serializable. That might involve making some fields transient, but then those fields won't be saved in the session. You'll also need to make the class implement Serializable.

I suggest you look at the documentation for Serializable, which goes into a fair amount of detail about serialization.