javax.faces.context

Class ExceptionHandler

java.lang.Object

javax.faces.context.ExceptionHandler

All Implemented Interfaces:

EventListener, FacesListener, SystemEventListener

Direct Known Subclasses:

ExceptionHandlerImpl, 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 specification prose 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 JSF.6.2 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 JSF.6.2.

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(javax.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, javax.faces.lifecycle.Lifecycle) calling ExceptionHandlerFactory.getExceptionHandler().

Since:

2.0

Constructor Summary

Constructors

Constructor and Description
ExceptionHandler()

Method Summary

Modifier and Type	Method and Description
abstract ExceptionQueuedEvent	getHandledExceptionQueuedEvent() Return the first ExceptionQueuedEvent handled by this handler.
abstract Iterable<ExceptionQueuedEvent>	getHandledExceptionQueuedEvents() The default implementation must return an Iterable over all ExceptionQueuedEvents that have been handled by the handle() method.
abstract Throwable	getRootCause(Throwable t) Unwrap the argument t until the unwrapping encounters an Object whose getClass() is not equal to FacesException.class or javax.el.ELException.class.
abstract Iterable<ExceptionQueuedEvent>	getUnhandledExceptionQueuedEvents() Return an Iterable over all ExceptionQueuedEvents that have not yet been handled by the handle() method.
abstract void	handle() Take action to handle the Exception instances residing inside the ExceptionQueuedEvent instances that have been queued by calls to Application().publishEvent(ExceptionQueuedEvent.class, eventContext).
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.
abstract void	processEvent(SystemEvent exceptionQueuedEvent) When called, the listener can assume that any guarantees given in the javadoc for the specific SystemEvent subclass are true.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

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 JSF.6.2.1.

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.

processEvent

public abstract void processEvent(SystemEvent exceptionQueuedEvent)
                           throws AbortProcessingException

When called, the listener can assume that any guarantees given in the javadoc for the specific SystemEvent subclass are true.

Specified by:

processEvent in interface SystemEventListener

Parameters:

exceptionQueuedEvent - the SystemEvent instance that is being processed.

Throws:

AbortProcessingException - if lifecycle processing should cease for this request.

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 javax.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