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POWhy use a JSF ExceptionHandlerFactory instead of <error-page> redirection?
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  1. POWhy use a JSF ExceptionHandlerFactory instead of <error-page> redirection?
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    copied!<p>All of the <code>ExceptionHandlerFactory</code> examples I have come across so far redirect a user to a <code>viewExpired.jsf</code> page in the event that a <code>ViewExpiredException</code> is caught:</p> <pre><code>public class ViewExpiredExceptionExceptionHandler extends ExceptionHandlerWrapper { private ExceptionHandler wrapped; public ViewExpiredExceptionExceptionHandler(ExceptionHandler wrapped) { this.wrapped = wrapped; } @Override public ExceptionHandler getWrapped() { return this.wrapped; } @Override public void handle() throws FacesException { for (Iterator&lt;ExceptionQueuedEvent&gt; i = getUnhandledExceptionQueuedEvents().iterator(); i.hasNext();) { ExceptionQueuedEvent event = i.next(); ExceptionQueuedEventContext context = (ExceptionQueuedEventContext) event.getSource(); Throwable t = context.getException(); if (t instanceof ViewExpiredException) { ViewExpiredException vee = (ViewExpiredException) t; FacesContext facesContext = FacesContext.getCurrentInstance(); Map&lt;String, Object&gt; requestMap = facesContext.getExternalContext().getRequestMap(); NavigationHandler navigationHandler = facesContext.getApplication().getNavigationHandler(); try { // Push some useful stuff to the request scope for use in the page requestMap.put("currentViewId", vee.getViewId()); navigationHandler.handleNavigation(facesContext, null, "/viewExpired"); facesContext.renderResponse(); } finally { i.remove(); } } } // At this point, the queue will not contain any ViewExpiredEvents. Therefore, let the parent handle them. getWrapped().handle(); } } </code></pre> <p>It seems to me that the following simple <code>web.xml</code> configuration is fundamentally the same and a lot simpler:</p> <pre><code>&lt;error-page&gt; &lt;exception-type&gt;javax.faces.application.ViewExpiredException&lt;/exception-type&gt; &lt;location&gt;/viewExpired.jsf&lt;/location&gt; &lt;/error-page&gt; </code></pre> <p>This prompts the question - why would one use an <code>ExceptionHandlerFactory</code>?</p>
 

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