public class FullAjaxExceptionHandler extends ExceptionHandlerWrapper
The FullAjaxExceptionHandler will transparently handle exceptions during ajax requests exactly the same way
as exceptions during synchronous (non-ajax) requests.
By default, when an exception occurs during a JSF ajax request, the enduser would not get any form of feedback if the
action was successfully performed or not. In Mojarra, only when the project stage is set to Development,
the enduser would see a bare JavaScript alert with only the exception type and message. It would make sense if
exceptions during ajax requests are handled the same way as exceptions during synchronous requests, which is
utilizing the standard Servlet API <error-page> mechanisms in web.xml.
This handler must be registered by a factory as follows in faces-config.xml in order to get it to run:
<factory>
<exception-handler-factory>org.omnifaces.exceptionhandler.FullAjaxExceptionHandlerFactory</exception-handler-factory>
</factory>
This exception handler will parse the web.xml and web-fragment.xml files to find the error
page locations of the HTTP error code 500 and all declared specific exception types. Those locations
need to point to Facelets files (JSP is not supported) and the URL must match the FacesServlet mapping (just
mapping it on *.xhtml should eliminate confusion about virtual URLs).
The location of the HTTP error code 500 or the exception type java.lang.Throwable is
required in order to get the FullAjaxExceptionHandler to work, because there's then at least a fall
back error page whenever there's no match with any of the declared specific exceptions. So, you must at least have
either
<error-page>
<error-code>500</error-code>
<location>/WEB-INF/errorpages/500.xhtml</location>
</error-page>
or
<error-page>
<exception-type>java.lang.Throwable</exception-type>
<location>/WEB-INF/errorpages/500.xhtml</location>
</error-page>
You can have both, but the java.lang.Throwable one will always get precedence over the 500
one, as per the Servlet API specification, so the 500 one would be basically superfluous.
The exception detail is available in the request scope by the standard Servlet error request attributes like as in a normal synchronous error page response. You could for example show them in the error page as follows:
<ul>
<li>Date/time: #{of:formatDate(now, 'yyyy-MM-dd HH:mm:ss')}</li>
<li>User agent: #{header['user-agent']}</li>
<li>User IP: #{request.remoteAddr}</li>
<li>Request URI: #{requestScope['javax.servlet.error.request_uri']}</li>
<li>Ajax request: #{facesContext.partialViewContext.ajaxRequest ? 'Yes' : 'No'}</li>
<li>Status code: #{requestScope['javax.servlet.error.status_code']}</li>
<li>Exception type: #{requestScope['javax.servlet.error.exception_type']}</li>
<li>Exception message: #{requestScope['javax.servlet.error.message']}</li>
<li>Stack trace:
<pre>#{of:printStackTrace(requestScope['javax.servlet.error.exception'])}</pre>
</li>
</ul>
Exceptions during render response can only be handled when the javax.faces.FACELETS_BUFFER_SIZE is
large enough so that the so far rendered response until the occurrence of the exception fits in there and can
therefore safely be resetted. When rendering of the error page itself fails due to a bug in the error page itself
and the response can still be resetted, then a hardcoded message will be returned informing the developer about the
double mistake.
When the rendering of the error page itself failed due to a bug in the error page itself, then the
FullAjaxExceptionHandler will reset the response and display a hardcoded error message in "plain text".
Note that the FullAjaxExceptionHandler does not deal with normal (non-ajax) requests at all. To properly
handle JSF and EL exceptions on normal requests as well, you need an additional FacesExceptionFilter. This
will extract the root cause from a wrapped FacesException and ELException before delegating the
ServletException further to the container (the container will namely use the first root cause of
ServletException to match an error page by exception in web.xml).
FullAjaxExceptionHandler
If more fine grained control is desired for determining the root cause of the caught exception, or whether it should
be handled, or determining the error page, or logging the exception, then the developer can opt to extend this
FullAjaxExceptionHandler and override one or more of the following protected methods:
findExceptionRootCause(FacesContext, Throwable)
shouldHandleExceptionRootCause(FacesContext, Throwable)
findErrorPageLocation(FacesContext, Throwable)
logException(FacesContext, Throwable, String, String, Object...)
Don't forget to create a custom ExceptionHandlerFactory for it as well, so that it could be registered
in faces-config.xml. This does not necessarily need to extend from
FullAjaxExceptionHandlerFactory.
FullAjaxExceptionHandlerFactory| Constructor and Description |
|---|
FullAjaxExceptionHandler(ExceptionHandler wrapped)
Construct a new ajax exception handler around the given wrapped exception handler.
|
| Modifier and Type | Method and Description |
|---|---|
protected String |
findErrorPageLocation(FacesContext context,
Throwable exception)
Determine the error page location based on the given exception.
|
protected Throwable |
findExceptionRootCause(FacesContext context,
Throwable exception)
Determine the root cause based on the caught exception, which will then be used to find the error page location.
|
ExceptionHandler |
getWrapped() |
void |
handle()
Handle the ajax exception as follows, only and only if the current request is an ajax request with an uncommitted
response and there is at least one unhandled exception:
Find the root cause of the exception by
findExceptionRootCause(FacesContext, Throwable). |
protected void |
logException(FacesContext context,
Throwable exception,
String location,
String message,
Object... parameters)
Log the thrown exception and determined error page location with the given message, optionally parameterized
with the given parameters.
|
protected boolean |
shouldHandleExceptionRootCause(FacesContext context,
Throwable exception)
Returns
true if the FullAjaxExceptionHandler should handle this exception root cause. |
getHandledExceptionQueuedEvent, getHandledExceptionQueuedEvents, getRootCause, getUnhandledExceptionQueuedEvents, isListenerForSource, processEventpublic FullAjaxExceptionHandler(ExceptionHandler wrapped)
wrapped - The wrapped exception handler.public void handle()
throws FacesException
findExceptionRootCause(FacesContext, Throwable).
findErrorPageLocation(FacesContext, Throwable).
handle in class ExceptionHandlerWrapperFacesExceptionprotected Throwable findExceptionRootCause(FacesContext context, Throwable exception)
Exceptions.unwrap(Throwable).context - The involved faces context.exception - The caught exception to determine the root cause for.protected boolean shouldHandleExceptionRootCause(FacesContext context, Throwable exception)
true if the FullAjaxExceptionHandler should handle this exception root cause. If
this returns false, then the FullAjaxExceptionHandler will skip handling this exception and
delegate it further to the wrapped exception handler. The default implementation just returns true.context - The involved faces context.exception - The caught exception to determine the root cause for.true if the given exception should be handled by the FullAjaxExceptionHandler.protected String findErrorPageLocation(FacesContext context, Throwable exception)
WebXml.findErrorPageLocation(Throwable).context - The involved faces context.exception - The exception to determine the error page for./ and be relative to the context path.protected void logException(FacesContext context, Throwable exception, String location, String message, Object... parameters)
java.util.logging as SEVERE.context - The involved faces context.exception - The exception to log.location - The error page location.message - The log message.parameters - The log message parameters, if any.public ExceptionHandler getWrapped()
getWrapped in interface FacesWrapper<ExceptionHandler>getWrapped in class ExceptionHandlerWrapperCopyright © 2012–2015 OmniFaces. All rights reserved.