JSF Under the Hood—Part 1 - JSF and HTML5 - page 59

Finally, registering the custom exception handler factory class in the faces-config.xml file, which is
added to the firstApplication example. Listing 2-37 shows the custom exception handler class which extends the
ExceptionHandlerWrapper class which is added to the firstApplication example.
Listing 2-37. The CustomExceptionHandler Class
package com.jsfprohtml5.firstapplication.exceptions;
import java.util.Iterator;
import javax.faces.FacesException;
import javax.faces.application.NavigationHandler;
import javax.faces.context.ExceptionHandler;
import javax.faces.context.ExceptionHandlerWrapper;
import javax.faces.context.FacesContext;
import javax.faces.event.ExceptionQueuedEvent;
import javax.faces.event.ExceptionQueuedEventContext;
public class CustomExceptionHandler extends ExceptionHandlerWrapper {
private ExceptionHandler wrapped;
public CustomExceptionHandler(ExceptionHandler wrapped) {
this.wrapped = wrapped;
}
@Override
public ExceptionHandler getWrapped() {
return wrapped;
}
@Override
public void handle() throws FacesException {
Iterator i = getUnhandledExceptionQueuedEvents().iterator();
while (i.hasNext()) {
ExceptionQueuedEvent event = (ExceptionQueuedEvent) i.next();
ExceptionQueuedEventContext context = (ExceptionQueuedEventContext) event.getSource();
Throwable t = context.getException();
FacesContext fc = FacesContext.getCurrentInstance();
try {
/* Here you can use the Throwable object in order to verify the exceptions you want to handle
in the application */
NavigationHandler navigationHandler = fc.getApplication().getNavigationHandler();
navigationHandler.handleNavigation(fc, null, "error?faces-redirect=true");