Why does Authorization Redirect Fail on JSF Form Submissions When Using a Custom FacesServlet?

Authorization Redirect on Session Expiration in JSF Form Submissions

Problem:

In a JSF application, a custom FacesServlet has been implemented to perform authorization checks and redirect users to the login page if not logged in. This works as expected during page navigation, but when a JSF form is submitted, the redirect fails and the user remains on the same page.

Cause:

The issue arises because the JSF command link/button triggers an Ajax request, which expects an XML response. However, the sendRedirect() method sends a regular HTML page that the Ajax engine cannot interpret. As a result, the redirect is not performed and the page remains unchanged.

Solution:

1. Use a Servlet Filter:

Instead of using a custom servlet, a servlet filter should be used for authorization checks. This is the recommended approach as it is more tailored to the task.

2. Handle Ajax Requests Differently:

In the filter, handle Ajax requests separately. Instead of sending a redirect, send a special XML response that instructs the JSF Ajax engine to perform a redirect.

Example Filter:

<code class="java">import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class AuthorizationFilter implements Filter {

    private static final String AJAX_REDIRECT_XML = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" +
        "<partial-response><redirect url='\"%s\"'></redirect></partial-response>";

    @Override
    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;
        HttpSession session = request.getSession(false);

        String loginURL = request.getContextPath() + "/login.xhtml";

        boolean loggedIn = (session != null) && (session.getAttribute("user") != null);
        boolean ajaxRequest = "partial/ajax".equals(request.getHeader("Faces-Request"));

        if (loggedIn || ajaxRequest) {
            chain.doFilter(request, response);
        } else if (ajaxRequest) {
            response.setContentType("text/xml");
            response.setCharacterEncoding("UTF-8");
            response.getWriter().printf(AJAX_REDIRECT_XML, loginURL);
        } else {
            response.sendRedirect(loginURL);
        }
    }
}</code>

By following these steps, the authorization redirect functionality can be implemented correctly for both page navigation and JSF form submissions.

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