ProgressBar

        <script type="text/javascript">
            function begin()
            {
                this.progressInterval = setInterval (
                function()
                {
                    clientSideBar.setValue(clientSideBar.getValue() + 10);
                }
                , 2000);
            }

            function stop()
            {
                clearInterval(this.progressInterval);
                clientSideBar.setValue(0);
            }
        </script>
        ...
        <ace:panel>
            <ace:progressBar widgetVar="clientSideBar" />
        </ace:panel>
        ...
        <h:commandButton onclick="begin();" ... />
        <h:commandButton onclick="stop();" ... />

                                  <ace:progressBar   id="myProgressBar"
                                                                widgetVar="#{upload.widgetVarName}"
                                                                ajax="true"
                                                                interval="2000"
                                                                value="#{upload.progressValue}"
                                                                completeListener="#{progressBarPolling.completeListener}"
                                                                onCompleteUpdate=":exampleForm">
                                 </ace:progressBar>
                             </ace:column>

                             <ace:column footerText="Action">
                                 <h:commandButton value="upload" type="button" onclick="#{upload.widgetVarName}.start();" rendered="#{not upload.active}"/>
                             </ace:column>