Problem with global ExceptionHandler showing errors in a dialog box

Question

Our use case is that whenever an exception occurs, instead of going to the default text page which shows the exception (which can be custom designed using <error-page> in web.xml), the exception should be shown in an error popup dialog box on the same page. Now as I understand this is very easily achievable by creating your own class extending ExceptionHandlerWrapper (creating it's factory class and referencing it in faces-config.xml) and implementing it's handle() function. The following is the main code snippet (stripped-down):
    @Override
    public void handle() throws FacesException
        FacesContext fc = FacesContext.getCurrentInstance();
        //Handle unhandled exceptions only if we have a FacesContext & ViewRoot
        if (fc != null && fc.getViewRoot() != null) {
            Iterator<ExceptionQueuedEvent> it = getUnhandledExceptionQueuedEvents().iterator();
            while (it.hasNext()) {
                ExceptionQueuedEvent event = it.next();
                ExceptionQueuedEventContext ectx = event.getContext();
                //Get the concerned exception
                Throwable t = ectx.getException();
                //Do not process JVM Errors
                if (!(t instanceof VirtualMachineError)) {
                    //Log the exception
                    logger.error("Faces Handled Exception", t);
                    //Make ADF create a global error popup dialog
                    FacesMessage fm = new FacesMessage(t.toString());
                    fm.setSeverity(FacesMessage.SEVERITY_ERROR);
                    fc.addMessage(null, fm);
                    //Exception handled. Now remove it
                    it.remove();
        //Call parent handler to do whatever it wants
        getWrapped().handle();
    }This works perfectly when the page is loaded and some action triggers an exception. Where this does fail is when an exception occurs when a manual navigation or re-direct happens (I haven't tested it out for faces navigation though). In this case, where I would have seen a textual representation of the exception stack trace in the normal scenario, the exception gets handled by the exception handler, it gets FacesContext and UIViewRoot instances and add's the corresponding FacesMessage, but the message is never shown (probably because the page never got created since the exception happened in the middle of it's creation) and we get an empty page or the concerned component is not rendered (in the case of composite components). This is very bad for the user experience since the user doesn't know that an error has occurred and only the logs can specify that.
I would like to know how can I detect the right time to add FacesMessage to FacesContext so to be sure that ADF will render it as a popup in the page. Whenever I detect it's not the right time, I'll let the parent handler handle it so that the user is shown the exception page.

Answer 1

Hi,
if this is not a generic ADF Faces questions but ADF and task flow related then read this: http://www.oracle.com/technetwork/issue-archive/2013/13-mar/o23adf-1897193.html
Frank