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.

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private boolean isAJAXRequest(HttpServletRequest request) {     boolean check = false;     String facesRequest = request.getHeader("Faces-Request");     if (facesRequest != null && facesRequest.equals("partial/ajax")) {         check = true;     }     return check; }

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.

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String redirectURL = response.encodeRedirectURL(request.getContextPath() + TARGET);   if (isAJAXRequest(request)) {     StringBuilder sb = new StringBuilder();     sb.append("<?xml version=\"1.0\" encoding=\"UTF-8\"?><partial-response><redirect url=\"").append(redirectURL).append("\"></redirect></partial-response>");     response.setHeader("Cache-Control", "no-cache");     response.setCharacterEncoding("UTF-8");     response.setContentType("text/xml");     PrintWriter pw = response.getWriter();     pw.println(sb.toString());     pw.flush(); }