ajax - Why FullAjaxExceptionHandler does not simply perform an ExternalContext#redirect()? -

in omnifaces, fullajaxexceptionhandler, after having found right error page use, calls jsf runtime build view , render instead of page includes ajax call.

why this? imho simpler perform externalcontext#redirect()? there specific reasons this?

_{we writing our own exceptionhandler based on fullajaxexceptionhandler , wanted understand reason behind design.}

the primary goal of fullajaxexceptionhandler let exceptions during ajax requests behave exactly same exceptions during non-ajax requests. developer must able reuse error pages across both conditions without worrying condition while implementing error pages.

a redirect isn't part of normal flow during non-ajax requests. default <error-page> mechanism in web.xml performs forward display error page, not redirect. if redirect performed, error page request attributes such javax.servlet.error.exception lost , render null. moreover, normal practice place error pages in /web-inf prevent endusers being able directly access (and bookmark , share) them. redirect require them publicly accessible, indicates major design problem (is intented target page real error page?).

if need perform redirect to/from error page, either homegrow custom exception handler explicitly invokes externalcontext#redirect() , doesn't utilize web.xml <error-page> mechanism, or add <meta http-equiv="refresh" ...> html head of error page in question (example here).

in case intended redirect login page when viewexpiredexception occurs, should realize there's big difference between cases of "user not logged in" , "session/view expired". former, should not catching viewexpiredexception @ all, use simple servlet filter checks if user logged in , redirect accordingly, long before facesservlet invoked. normal authentication framework (jaas, shiro, spring security, etc) works way.

see also:

• what approach forward exception servlets jsp page?
• what difference between redirect , navigation/forward , when use what?
• why use jsf exceptionhandlerfactory instead of <error-page> redirection?
• check if session exists jsf
• authorization redirect on session expiration not work on submitting jsf form, page stays same