Package jakarta.faces.context

Class ExceptionHandler

  • All Implemented Interfaces:
    FacesListener, SystemEventListener, EventListener
    Direct Known Subclasses:
    ExceptionHandlerWrapper
    public abstract class ExceptionHandler
extends Object
implements SystemEventListener

    ExceptionHandler is the central point for handling unexpected Exceptions that are thrown during the Faces lifecycle. The ExceptionHandler must not be notified of any Exceptions that occur during application startup or shutdown.

    See the Jakarta Faces Specification Document for the requirements for the default implementation. Exceptions may be passed to the ExceptionHandler in one of two ways:

    • by ensuring that Exceptions are not caught, or are caught and re-thrown.

      This approach allows the ExceptionHandler facility specified in section 6.2 "ExceptionHandler" of the Jakarta Faces Specification Document to operate on the Exception.

    • By using the system event facility to publish an ExceptionQueuedEvent that wraps the Exception.

      This approach requires manually publishing the ExceptionQueuedEvent, but allows more information about the Exceptionto be stored in the event. The following code is an example of how to do this. 

       

 //...
 } catch (Exception e) {
   FacesContext ctx = FacesContext.getCurrentInstance();
   ExceptionQueuedEventContext eventContext = new ExceptionQueuedEventContext(ctx, e);
   eventContext.getAttributes().put("key", "value");
   ctx.getApplication().publishEvent(ExceptionQueuedEvent.class, eventContext);
 }

      Because the Exception must not be re-thrown when using this approach, lifecycle processing may continue as normal, allowing more Exceptions to be published if necessary.

    With either approach, any ExceptionQueuedEvent instances that are published in this way are accessible to the handle() method, which is called at the end of each lifecycle phase, as specified in section 6.2 "ExceptionHandler" of the Jakarta Faces Specification Document.

    Note that if handle() happens to be invoked during PhaseId.RENDER_RESPONSE, the recovery options are more limited than when it is invoked during other phases. Specifically, it is not valid to call NavigationHandler.handleNavigation(jakarta.faces.context.FacesContext, java.lang.String, java.lang.String) during RENDER_RESPONSE.

    Instances of this class are request scoped and are created by virtue of FacesContextFactory.getFacesContext(java.lang.Object, java.lang.Object, java.lang.Object, jakarta.faces.lifecycle.Lifecycle) calling ExceptionHandlerFactory.getExceptionHandler().

    Since:
    2.0

    • Constructor Detail

      • ExceptionHandler

        public ExceptionHandler()

    • Method Detail

      • handle

        public abstract void handle()
                     throws FacesException

        Take action to handle the Exception instances residing inside the ExceptionQueuedEvent instances that have been queued by calls to Application().publishEvent(ExceptionQueuedEvent.class, eventContext). The requirements of the default implementation are detailed in section 6.2.1 "Default ExceptionHandler implementation" of the Jakarta Faces Specification Document.

        Throws:
        FacesException - if and only if a problem occurs while performing the algorithm to handle the Exception, not as a means of conveying a handled Exception itself.
        Since:
        2.0

      • getHandledExceptionQueuedEvent

        public abstract ExceptionQueuedEvent getHandledExceptionQueuedEvent()

        Return the first ExceptionQueuedEvent handled by this handler.

        Returns:
        instance of ExceptionQueuedEvent.

      • getUnhandledExceptionQueuedEvents

        public abstract Iterable<ExceptionQueuedEvent> getUnhandledExceptionQueuedEvents()

        Return an Iterable over all ExceptionQueuedEvents that have not yet been handled by the handle() method.

        Returns:
        the unhandled set of ExceptionQueuedEvents.

      • getHandledExceptionQueuedEvents

        public abstract Iterable<ExceptionQueuedEvent> getHandledExceptionQueuedEvents()

        The default implementation must return an Iterable over all ExceptionQueuedEvents that have been handled by the handle() method.

        Returns:
        an Iterable over all ExceptionQueuedEvents.

      • isListenerForSource

        public abstract boolean isListenerForSource​(Object source)

        This method must return true if and only if this listener instance is interested in receiving events from the instance referenced by the source parameter.

        Specified by:
        isListenerForSource in interface SystemEventListener
        Parameters:
        source - the source that is inquiring about the appropriateness of sending an event to this listener instance.
        Returns:
        the value as specified above

      • getRootCause

        public abstract Throwable getRootCause​(Throwable t)

        Unwrap the argument t until the unwrapping encounters an Object whose getClass() is not equal to FacesException.class or jakarta.el.ELException.class. If there is no root cause, null is returned.

        Parameters:
        t - passed-in wrapped Throwable.
        Returns:
        unwrapped object.
        Throws:
        NullPointerException - if argument t is null.
        Since:
        2.0