java.lang.IllegalStateException: Cannot call sendRedirect() after the response has been committed

Question

I am calling java servlet for logout from my page setting all the values to null and reset the http session as follows:

public class logout extends HttpServlet
{
    public void service(HttpServletRequest rq,HttpServletResponse rs)throws IOException,ServletException
    {
        try{
            HttpSession ss=rq.getSession(false);
            if(ss.getAttribute("uid")==null || ss.getAttribute("usr")==null || ss.getAttribute("acc")==null)
            {
                rs.sendRedirect("/");
            }

            rs.setHeader("Cache-Control","no-cache, no-store, must-revalidate"); 
            rs.addHeader("Cache-Control", "post-check=0, pre-check=0");
            rs.setHeader("Pragma","no-cache"); 
            rs.setDateHeader ("Expires", 0);    
            HttpSession session = rq.getSession(false);
            session.setAttribute("uid",null);
            session.setAttribute("usr",null);
            session.setAttribute("acc",null);
            session.invalidate();
            rs.sendRedirect("/");
        }
        catch(Exception exp)
        {
            //Catch
        }


    }
}

If I click the logout button then it get logout fine. Suppose if I am not logout for some time suppose 30 minutes then press logout button I am getting a blank page instead of redirecting to home page. In stacktrace i got the erroe as following:

java.lang.IllegalStateException: Cannot call sendRedirect() after the response has been committed
    org.apache.catalina.connector.ResponseFacade.sendRedirect(ResponseFacade.java:494)
    logout.service(logout.java:32)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

I know that it is going to catch because session will expire automatically. How can I handle this? I need to redirect to home page even if it the session expires automatically. What should I do?

please print stack trace of error here. – Chetan Verma Jun 18 '15 at 16:49 — Chetan Verma, Jun 18 '15 at 16:49

faheem farhan · Answer 1 · 2015-06-18T19:26:48.717

-1

If the container's session is expired, then this line

HttpSession ss=rq.getSession(false);

will return null.

You are not checking for not null before using ss variable, which might be throwing exception at runtime.

And also, you need not have one more variable for holding session, You can reuse ss.

     if(ss != null){
            if(ss.getAttribute("uid")==null || ss.getAttribute("usr")==null || ss.getAttribute("acc")==null)
                        {
                           // rs.sendRedirect("/");
                        }else{        
                        rs.setHeader("Cache-Control","no-cache, no-store, must-revalidate"); 
                        rs.addHeader("Cache-Control", "post-check=0, pre-check=0");
                        rs.setHeader("Pragma","no-cache"); 
                        rs.setDateHeader ("Expires", 0);    

                        ss.setAttribute("uid",null);
                        ss.setAttribute("usr",null);
                        ss.setAttribute("acc",null);
                        ss.invalidate();
                      //  rs.sendRedirect("/");
    }
        }
rs.sendRedirect("/");

edited Jun 18 '15 at 19:26

answered Jun 18 '15 at 17:10

faheem farhan

401
2
9

ok. So you are saying that I need to check ss == null before going to try???Can you post as an answer then it will be helpful!! – Santhucool Jun 18 '15 at 17:18
See the updated response. – faheem farhan Jun 18 '15 at 19:02
Getting error page Error mentioned above. I have updated question!! – Santhucool Jun 18 '15 at 19:08
Remove or comment the rs.sendRedirect("/") from if block. – faheem farhan Jun 18 '15 at 19:18
If I do so, then how it will redirect to home page??? – Santhucool Jun 18 '15 at 19:19
See the updated again. – faheem farhan Jun 18 '15 at 19:27
Let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/80926/discussion-between-faheem-farhan-and-santhucool). – faheem farhan Jun 18 '15 at 19:28
It will never make me logout even if my session expires!! – Santhucool Jun 18 '15 at 19:46
Solved it. Thank 4 ur help!! – Santhucool Jun 18 '15 at 20:12

score -1 · Answer 2 · answered Jun 18 '15 at 20:11

-1

Added some changes in my catch(){} block as following, now works fine.

catch(Exception exp)
        {
            RequestDispatcher dd = rq.getRequestDispatcher("/");
            dd.forward(rq, rs);
        }

answered Jun 18 '15 at 20:11

Santhucool

1,656
2
36
92

java.lang.IllegalStateException: Cannot call sendRedirect() after the response has been committed

2 Answers2