[richfaces-issues] [JBoss JIRA] Commented: (RF-5955) a4j push fails(sometimes) to rerender target component

[Nick Belaevski (JIRA)]

    [ https://jira.jboss.org/jira/browse/RF-5955?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12451372#action_12451372 ] 

Nick Belaevski commented on RF-5955:
------------------------------------

Looks like the concurrent access issue.
Please use client-side events queue (either by specifying eventsQueue attribute or by declaring view/form scoped queue) and dispatcher bean on server that will control re-rendering (you can do that by specifying reRender="#{bean.elementsToUpdate}")

> a4j push fails(sometimes) to rerender target component
> ------------------------------------------------------
>
>                 Key: RF-5955
>                 URL: https://jira.jboss.org/jira/browse/RF-5955
>             Project: RichFaces
>          Issue Type: Bug
>    Affects Versions: 3.3.0
>         Environment: JBoss AS: 4.2.2 GA
> JBoss Seam: 2.1.1GA
> JBoss RichFaces: 3.3.0 GA 
> OS: Windows XP
> Browser: Firefox 3.0.5 and IE 7
>            Reporter: Atul Kshirsagar
>
> a4j push tag fails to reRender the target component (specified in reRender attribute) sometimes.  
> In our project we are using a4j:push tag to dynamically refresh certain portions of our web page depending upon events generated on server side. The problem that I am seeing is that some times (not always) a4j push does not reRender the target id specified even though PushEventListener is notified of an Event.
> Note that I have 8 a4j push tags refreshing different components on our web page and we can see burst of events (approx 200 events in less than 1 min).
> Below given is the example code:
> xhtml that uses a4j:push tag:
> <a4j:push reRender="myTableId" eventProducer="#{myBean.addListener}" interval="10000" 
> 			ignoreDupResponses="true" action="#{mybean.populateViewModel}"/>		
> <rich:dataTable id="myTableId" value="#{myBean.data}" var="_data">
> <rich:column>
> <h:outputText value="#{_data.name}" />
> </rich:column>
> </rich:dataTable>
> 	
> Backing bean definition is as follows:
> @Stateful
> @Local( {
>   MyBeanLocal.class
> })
> @Name("myBean")
> @Scope(ScopeType.SESSION)
> @Restrict("#{identity.loggedIn}")
> public class MyBean implements MyBeanLocal, Serializable {
>   @EJB
>   private MyEJB ejb;
>   private MyBeanListener eventListener;
>  /**
>    * DataModel
>    */
>   private List<Data> data;
>   
>   public List<Data> getData() {
>       return this.data;
>   }
> @Create
>   public void create() {
>      this.data = new ArrayList<Data>();
>      populateViewModel();
>   }
> // destroy method de-registers the listener from DataModel
>   @Remove
>   @Destroy
>   public void destroy() {
>      DataModel dataModel = ejb.getDataModel();
>     if (dataModel != null) {      
>       dataModel.removeChangeListener(eventListener);
>     }
>   }
> /**
>    * Adds listener for conveying AJAX events.
>    * 
>    * @param listener
>    */
>   public void addListener(EventListener listener) {
>         DataModel dataModel = ejb.getDataModel();    
>         eventListener = new MyBeanListener();
>         eventListener.addListener(listener);
>        dataModel.addChangeListener(eventListener);
>   }
>   /**
>    * Constructs the view data model required for the link utilization widget on dashboard
>    */
>   public void populateViewModel() {
>     data.clear();
>     DataModel dataModel = ejb.getDataModel();
>     data = dataModel.getData();
>   }
> }	
> public class MyBeanListener implements Serializable {
>   private PushEventListener listener;
>   public void addListener(EventListener l) {
>       this.listener = (PushEventListener)l;
>   }
>   public void dataChanged() {
>      listener.onEvent(new EventObject(this));
>   }
> }
> 	
> public class DataModel implements MessageListener {
>    private List<MyBeanListener> listeners;
>    
>    public void addChangeListener(MyBeanListener l) {
>        listeners.add(l);
>    }
>    public void removeChangeListener(MyBeanListener l) {
>        listeners.remove(l);
>    }
>    public void fireEvent() {
>       for (MyBeanListener l: listeners) {
>          l.dataChanged();
>       }
>    }
>    // This method is called on JMS message
>    public void onMessage(Message message) {
>       // update internal data structure and then notify listeners
>       fireEvent();
>    }
> }	
> So what is happening here is that class MyBean is SFSB and registers MyBeanListener with DataModel when addListener is called (by virtue of eventProducer attribute of a4j:push). DataModel is a JMS listener and upon receiving JMS message it notifies the registered listener of change in data.
> What I am seeing here is that all the above described flow happens and a4j:push gets notified of the event (I verified this by checking that populateViewData method of MyBean gets called) but the reRender of 'myTableId' component does not happen (this happens only intermittently...e.g If I repeat the test for about 4 to 5 times I will see it happening once). I debugged it using a4j:log component and found that sometimes the ajax response does not contain the component with id 'myTableId'.

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