Thursday, January 24, 2013

JSF 2.x Tip of the Day: AJAX Redirection from @WebFilter (Filter)

I was working on an application where I needed to have it redirect to a login page when certain conditions exist in the application, e.g. session timeout, etc. A ViewExpiredException custom exception handler (available in JSF 2.0) can handle this case, but I had a need for another type of "Session" object to be monitored to determine if I should redirect based on its status. The other object was stored in the HttpSession object as an attribute so I decided to handle it with a Filter (@WebFilter).

The first thing is to determine if the request is a partial/ajax request. If it is a normal post, we can handle it with a HttpResponse.sendRedirect(String location) mechanism. If it is AJAX, we need to handle it in a completely different manner. Once I determined that the request was AJAX, I needed to be able to pass the appropriate response back to the JSF page in a format that it could understand. A great tip came from Jim Driscoll's blog: Redirecting from a JSF 2.0 Ajax Request which gave me the general syntax for what I needed to send back.

Note: This is being intercepted in a Filter so I don't have access to the FacesContext. Here is a partial code snippet of how to send the redirect. You would need to set the variable TARGET to go to the desired location.


Markus Eisele said...

Hi John,

thanks for that post. I love to follow your JSF experiences and tips.
Just a short head ups, that there actually _IS_ a way to get hand on the FacesContext in Filters and Servlets ...
please compare what Lincoln and BalusC wrote:

- M

John Yeary said...

Those are some great blog posts. ;-)

In my case, I had some external actors on my application that cause a state holder in the application to timeout (outside of JSF). This timeout could occur if some navigated to a page and just let it sit until it timed out. There is a filter which checks the state holder, and I needed a mechanism to redirect in a very simple manner back to a login page in JSF.

The details I posted are a simple solution to a PITA problem that was added to the requirements after the code for the application was written.

If I had to do it again, knowing about these blog posts I would have reconsidered it. However, I think my solution is simple.

If you take the posts lists, and combined them with the code from Jim Driscoll's blog you would have another solution where you could do some more complex processing.

I will keep the information you added in my archive of useful tips.

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