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Java Enterprise Edition (EE)

ExceptionHandler


javax.faces.context
Class ExceptionHandler

java.lang.Object
  javax.faces.context.ExceptionHandler
All Implemented Interfaces:
java.util.EventListener, FacesListener, SystemEventListener
Direct Known Subclasses:
ExceptionHandlerWrapper
public abstract class ExceptionHandler
extends java.lang.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.

Instances of this class are request scoped and are created by virtue of FacesContextFactory#getFacesContext calling ExceptionHandlerFactory#getExceptionHandler.

Since:
2.0

Constructor Summary
ExceptionHandler()
           
 
Method Summary
abstract  ExceptionQueuedEvent getHandledExceptionQueuedEvent()
          

Return the first ExceptionQueuedEvent handled by this handler.

abstract  java.lang.Iterable<ExceptionQueuedEvent> getHandledExceptionQueuedEvents()
          

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

abstract  java.lang.Throwable getRootCause(java.lang.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  java.lang.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(java.lang.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.

getUnhandledExceptionQueuedEvents

public abstract java.lang.Iterable<ExceptionQueuedEvent> getUnhandledExceptionQueuedEvents()

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

getHandledExceptionQueuedEvents

public abstract java.lang.Iterable<ExceptionQueuedEvent> getHandledExceptionQueuedEvents()

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

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(java.lang.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.

getRootCause

public abstract java.lang.Throwable getRootCause(java.lang.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.

Throws:
java.lang.NullPointerException - if argument t is null.
Since:
2.0


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