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Prevent the same object from communicating with two different sessions in sleep mode

Using jsf 1.2, hibernate, richfaces 3.3.0GA and facelets.

I have this code in my bean support:

public List<Rater> getFreeRaters(){
    GP myGP = (GP) user;
    update(myGP.getContract());
    ArrayList<Rater> raters = new ArrayList<Rater>(myGP.getContract().getRaters());
    ArrayList<Rater> selectedRaters = this.getSelectedRaters();
    raters.removeAll(selectedRaters);
    return raters;

}

and this code for the interface:

<a4j:form id="gradersForm" ajaxSingle="true">
    <rich:listShuttle sourceValue="#{user.gradersTab.freeRaters}" id="gradersTab_listShuttle"
    targetValue="#{user.gradersTab.selectedRaters}" var="rater" listsHeight="150"
        sourceListWidth="130" targetListWidth="130" sourceCaptionLabel="Available Items"
        targetCaptionLabel="Currently Active Items" > 
        <rich:column>
            <h:outputText value="#{rater.username}"></h:outputText>
        </rich:column>
    </rich:listShuttle>         
    <a4j:commandButton value="Save"></a4j:commandButton>

</a4j:form>

This is my session filter:

public class HibernateSessionRequestFilter implements Filter {

private static Log log = LogFactory.getLog(HibernateSessionRequestFilter.class);

private SessionFactory sf;

public void doFilter(ServletRequest request,
                     ServletResponse response,
                     FilterChain chain)
        throws IOException, ServletException {
    HttpServletResponse resp= (HttpServletResponse) response;
    try {
        log.info("Starting a database transaction");
        Session session = sf.getCurrentSession();
        session.beginTransaction();

        // Call the next filter (continue request processing)
        chain.doFilter(request, resp);

        // Commit and cleanup
        log.info("Committing the database transaction");

        session.getTransaction().commit();


    } catch (StaleObjectStateException staleEx) {...

The problem occurs when the user interface is re-displayed twice or more at the same time through AJAX. Being two different requests, each of them receives Session, and the object tries to connect to both of them at the same time, because none of them had enough time to complete and do session.close(), so hibernate throws an exception org.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions

Any suggestion to prevent this? Thanks.

Update: web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.5"
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"       xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-   app_2_5.xsd">
<display-name>eyeprevent</display-name>
<context-param>
<param-name>javax.faces.CONFIG_FILES</param-name>
<param-value>/WEB-INF/faces-config.xml</param-value>
</context-param>
<context-param>
<param-name>javax.faces.DEFAULT_SUFFIX</param-name>
<param-value>.xhtml</param-value>
</context-param>
<context-param>
<param-name>javax.faces.STATE_SAVING_METHOD</param-name>
<param-value>server</param-value>
</context-param>
<context-param>
<param-name>facelets.LIBRARIES</param-name>
<param-value>/WEB-INF/functions.taglib.xml</param-value>
</context-param>
<context-param>
<param-name>org.richfaces.SKIN</param-name>
<param-value>#{user.skin}</param-value>
</context-param>
<context-param>
<param-name>org.richfaces.CONTROL_SKINNING</param-name>
<param-value>enable</param-value>
</context-param>
<filter>
<filter-name>HibernateFilter</filter-name>
<filter-class>com.eyeprevent.util.HibernateSessionRequestFilter</filter-class>
</filter>
<filter>
<display-name>RichFaces Filter</display-name>
<filter-name>richfaces</filter-name>
<filter-class>org.ajax4jsf.Filter</filter-class>
</filter>
<filter-mapping>
<filter-name>HibernateFilter</filter-name>
<url-pattern>/pages/*</url-pattern>
</filter-mapping>
<filter-mapping>
<filter-name>HibernateFilter</filter-name>
<url-pattern>/upload/*</url-pattern>
</filter-mapping>

<filter-mapping>

<filter-name>richfaces</filter-name>
<servlet-name>Faces Servlet</servlet-name>
<dispatcher>REQUEST</dispatcher>
<dispatcher>FORWARD</dispatcher>
<dispatcher>INCLUDE</dispatcher>
</filter-mapping>
<listener>
<listener-class>com.sun.faces.config.ConfigureListener</listener-class>
</listener>
<listener>
<listener-class>com.eyeprevent.util.MySessionListener</listener-class>
</listener>
<servlet>
<display-name>EPConnectServlet</display-name>
<servlet-name>EPConnectServlet</servlet-name>
<servlet-class>com.eyeprevent.servlets.EPConnectServlet</servlet-class>
<init-param>
<param-name>imagePath</param-name>
<param-value>/home/pako/images</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet>
<servlet-name>imageServlet</servlet-name>
<servlet-class>com.eyeprevent.servlets.ImageServlet</servlet-class>
<init-param>
<param-name>imagePath</param-name>
<param-value>/home/pako/images</param-value>
</init-param>
</servlet>
<servlet>
<servlet-name>Faces Servlet</servlet-name>
<servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>EPConnectServlet</servlet-name>
<url-pattern>/upload/EPConnectServlet</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>imageServlet</servlet-name>
<url-pattern>/image/*</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>Faces Servlet</servlet-name>
<url-pattern>*.xhtml</url-pattern>
</servlet-mapping>
<session-config>
<session-timeout>0</session-timeout>
</session-config>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.xhtml</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
<welcome-file>pages/login.xhtml</welcome-file>
</welcome-file-list>
<error-page>
<error-code>404</error-code>
<location>/pages/error.xhtml</location>
</error-page>
<error-page>
<error-code>401</error-code>
<location>/pages/unauthorized.xhtml</location>
</error-page>
<login-config>
<auth-method>BASIC</auth-method>
</login-config>
</web-app>
+5
1

-, merge update ...

, merge ,

myInstance = (myInstanceClass) Session.merge(myInstance);
+2

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