ConcurrentModification Exception when calling actionlistener

[samvimes]

Hi Everyone,
in production environment sometimes a concurrent modification exception occurs if a specific acrion listener is called (see below) which in turn modifies an array list.

The page code looks like this...

<a4j:keepAlive beanName="userPage" ajaxOnly="true"/>
        <a4j:queue name="userPageQueue" size="10" ignoreDupResponses="true"/>

        <a4j:form id="searchForm" eventsQueue="userPageQueue">
          ...
         <a4j:commandButton id="btnDeleteButton" value="User löschen" styleClass="std_button" reRender="p_lblUserCount, p_dsrUsers, p_tblUsers,                     btnDeleteButton, editForm:userData"
                disabled="#{userPage.deleteButtonDisabled}" actionListener="#{userPage.deleteUsers}" />
          </a4j:form>
        <a4j:form id="editForm" eventsQueue="userPageQueue">
          ...
     </a4j:form>

I use a request scoped bean with a4j:keepAlive. As suggested in http://community.jboss.org/thread/16652?start=15&tstart=0 I used a queue to synchronize the method calls on the page. Since I still get a concurrent modification do I need to explicitly synchronize the method or use a session bean instead? What is the suggested way to solve this problem?

I use Facelets 1.1.4, JSF 1.2_13 on WebSphere 6.1

Best regards

Carsten

[ilya_shaikovsky]

post your bean code also please

[samvimes]

This is the called actionListener. Exception occurs while looping through the selected users with the iterator.

     public void deleteUsers(ActionEvent e) {
        releaseLock();
        resetDetails();
        userErrorMessages.clear();

        Mandator mandator = sessionContext.getMandator();
        UserTableEntry user;
        String msg;
            
        for (Iterator<UserTableEntry> currentUserList = users.iterator(); currentUserList
                .hasNext();) {
            user = currentUserList.next();

            if (user.isSelected()) {
                try {
                    msg = userService.deleteUser(user, mandator);

                    if (msg.equals(""))
                        currentUserList.remove();
                    else
                        userErrorMessages
                                .add(buildUserErrorMessage(user,
                                        msg));
                } catch (DataAccessException dae) {
                    logger.error(dae.getMessage(), dae);
                    ...
                }
            }
        }

        if (userErrorMessages.isEmpty()) {
            statusPopupRendered = true;
        } else {
            userResultPopupRendered = true;
        }
    }

[samvimes]

As a workaround I will explicitly synchronize the method call but are there no further suggestions?