FAQ

Either retrieve the current CVS version or add the following statement to the webapp context:

<Context ...>
    <Manager className="org.apache.catalina.session.PersistentManager" 
         saveOnRestart="false"/>
</Context>

Tomcat will print following Output: No Store configured, persistence disabled

Here is the solution for Glassfish:

You must have an sun-web.xml configuration file into the WEB-INF folder of your .war application package configured in this way:

<sun-web-app>    
 <session-config>      
    <session-manager>        
      <manager-properties>        
          <property name="sessionFilename" value="" />
      </manager-properties>      
     </session-manager>    
   </session-config>  
</sun-web-app>

More details on Jan Luehe's blog

Background: wingS dynamically tries to load and instantiate the PLAF (renderer) classes on session initialization and therefore consults the context class loader. If you stop your application Tomcat tries to serialized your session, hence the whole application state. If this failes (i.e. your classes are not fully serializable) the tomcat does not replace the classloader. So after refresh wingS only sees the outdated, old classlaoder which does no longer know the CG classes. We disabled the session serialization as a whole to avoid this in the future.