那各位指点那里错了 jsp servlet

type Exception report

message

description The server encountered an internal error () that prevented it from fulfilling this request.

exception

java.lang.IllegalStateException: Cannot forward after response has been committed
    com.servlet.loginlet.doPost(loginlet.java:97)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.13 logs.

   
 String code=request.getParameter("listscode");
        
String scode=(String) request.getSession().getAttribute("code");

       if(!lcode.equals("scode"))
         {
        request.setAttribute("error", "验证码不正确请重新输入");
        request.getRequestDispatcher("stulogin.jsp").forward(request, response);
        }
     加了这几句发生的错误