Request Errors Handling - actionlistener

[multanis]

Hello,

I just noticed that if an exception occurred in my action listener method, there is nothing displayed to the client side.

So I decided to fix this using

A4J.AJAX.onError = function(req, status, message) { alert('CRASH !');}

But it doesn't do anything ... The only way it works is when I shutdown my application (so I got a page not found)

I've added in my web.xml (I don't know if this is required but it is written in the dev guide):

<context-param>
    <param-name>org.ajax4jsf.handleViewExpiredOnClient</param-name>
    <param-value>true</param-value>

</context-param>

In my jspx:

<a4j:commandLink value="Save" actionListener="#{myBean.save}" eventsQueue="default"/>

MyBean.java:

public void save(ActionEvent event) {

     throw new NullPointerException();

}

I'm using richfaces 3.3.3-FINAL/Spring/Facelet (NOT MyFaces ;-) )

Many thanks for your light !

Update:

I succeeded to make it work, but it is a bit tricky and I'm not sure of the consequences:

I had to write my own AjaxViewRoot to redefine the processEvents method to let it throw AbortProcessingException.

faces-confix.xml:

     <component>
        <component-type>javax.faces.ViewRoot</component-type>
        <component-class>my.package.CustomViewRoot</component-class>
    </component>

CustomViewRoot:

    @Override
    public void processEvents(FacesContext context, EventsQueue phaseEventsQueue, boolean havePhaseEvents) {
        FacesEvent event;
        while (havePhaseEvents) {
            try {
                event = (FacesEvent) phaseEventsQueue.remove();
                UIComponent source = event.getComponent();
                source.broadcast(event);
            } catch (NoSuchElementException e) {
                havePhaseEvents = false;
            }
        }
    }

Is this acceptable ? Why is this exception catched in AjaxViewRoot ?

Request Errors HandlingBBB

[nbelaevski]

Nicolas,

That's how JSF 1.2 handles exception. See UIViewRoot sources for another example of such behavior. JSF 2.0 introduced special handler for exceptions.

[multanis]

Nick,

Thanks for your lights !

So is my solution correct ? Or is this dangerous for any reason and will break something later ?

[nbelaevski]

Nicolas,

Looking at the code I see that some things can break if AbortProcessingException won't be caught - e.g. phase listeners invocation at view root. I'd suggest to take a look at MyFaces 1.2 code - they have implemented exception handler as extension.

[multanis]

Nick,

I had a look in MyFaces 1.2 code but as far as I understand, they don't do anything with the AbortProcessingException.

Here is the code from UIViewroot (in myfaces-api-1.2.10):

    private void _broadcastForPhase(PhaseId phaseId)
    {
        if (_events == null)
        {
            return;
        }

        boolean abort = false;

        int phaseIdOrdinal = phaseId.getOrdinal();
        for (ListIterator<FacesEvent> listiterator = _events.listIterator(); listiterator
                .hasNext();)
        {
            FacesEvent event = listiterator.next();
            int ordinal = event.getPhaseId().getOrdinal();
            if (ordinal == ANY_PHASE_ORDINAL || ordinal == phaseIdOrdinal)
            {
                UIComponent source = event.getComponent();
                try
                {
                    source.broadcast(event);
                }
                catch (AbortProcessingException e)
                {
                    // abort event processing
                    // Page 3-30 of JSF 1.1 spec: "Throw an
                    // AbortProcessingException, to tell the JSF implementation
                    // that no further broadcast of this event, or any further
                    // events, should take place."
                    abort = true;
                    break;
                }
                finally
                {
                    try
                    {
                        listiterator.remove();
                    }
                    catch (ConcurrentModificationException cme)
                    {
                        int eventIndex = listiterator.previousIndex();
                        _events.remove(eventIndex);
                        listiterator = _events.listIterator();
                    }
                }
            }
        }

        if (abort)
        {
            // TODO: abort processing of any event of any phase or just of any
            // event of the current phase???
            clearEvents();
        }
    }

    private void clearEvents()
    {
        _events = null;
    }

Maybe I'm just not looking at the ritght place...

[nbelaevski]

Nicolas,

Compare MethodExpressionActionListener#processAction(ActionEvent) in Mojarra and MyFaces. In Mojarra you'll see that they are wrapping all exceptions into AbortProcessingEvent, while MyFaces doesn't do that.

[multanis]

Nick,

Many thanks for your answers !

As I don't know how to change the MethodExpressionActionListener#processAction implementation, I've modified my CustomViewRoot as follow:

     public void processEvents(FacesContext context, EventsQueue phaseEventsQueue, boolean havePhaseEvents) {
        FacesEvent event;
        while (havePhaseEvents) {
            try {
                event = (FacesEvent) phaseEventsQueue.remove();
                UIComponent source = event.getComponent();
                try {
                    source.broadcast(event);
                } catch (AbortProcessingException e) {

                    Throwable cause = e.getCause();
                    if (cause != null && cause instanceof AbortProcessingException) {
                        UIComponent component = event.getComponent();
                        String id = null != component ? component.getClientId(context) : "";
                        logger.error("Error processing faces event for the component " + id, e);
                    } else
                        throw e;
                }
            } catch (NoSuchElementException e) {
                havePhaseEvents = false;
            }
        }

    }

I think this is the closest I can do without redefining MethodExpressionActionListener, but if you know an easy way to do it, I will do it ;-)

Thanks again !

[nbelaevski]

Another solution can be not to use EL-expression but implement listener interface.

[multanis]

I'm probably a bit dumb but I don't know how to do that.

Is this what you are talking about ?

<h:commandButton value="Add">  
     <f:actionListener type="com.mycompany.MyListener" />
</h:commandButton>

And com.mycompany.MyListenerListener must implements ActionListener.

[nbelaevski]

Yes, that's it.

[multanis]

Ok many thanks for your help !

(I will not use the ActionListener interface because I don't want to change all my actionlistener but I keep it in mind for my next project)