My Exceptions

org.apache.catalina.connector.ResponseFacade.sendRedirect(ResponseFacade.java:435).

java.lang.IllegalStateException

At point of nothing to response to client (browser)

Following is sample example
if(a.equals("7")){
  RequestDispatcher dispatcher= getServletContext().getRequestDispatcher("/login.jsp");
   dispatcher.forward(request,response);

}

if(b.equals("6")){
  RequestDispatcher dispatcher= getServletContext().getRequestDispatcher("/login.jsp");
    dispatcher.forward(request,response);

}

In first  block itself it respond to browser . In step 2 nothing to response
so this exception will occur

To Avoid Exception java.lang.IllegalStateException.
Add return statement .
if(a.equals("7")){
      RequestDispatcher dispatcher= getServletContext().getRequestDispatcher("/login.jsp");
    dispatcher.forward(request,response);
      return;
}