为什么我的请求getRequestDispatcher（）进入ThreadPoolExceutor.java（1150）？

Question

我正在尝试将请求从Servlet重定向到JSP。我的要求是threadpoolexecutor。这是我的servlet代码。我正在编写doPost方法以节省时间。

protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {

    processRequest(request, response);
    String action=request.getParameter("action");
    HttpSession session=request.getSession();

    if(action==null){
        String user=request.getParameter("username");
        String pass=request.getParameter("password");
        boolean remember=request.getParameter("remember")!=null;
        ConnectionTest cn=new ConnectionTest();
        conn=cn.getConn();

        try{
            psmt=conn.prepareStatement(qry);
            psmt.setString(1, user);
            psmt.setString(2, pass);
            rs=psmt.executeQuery();

            if(rs.next()){
                session.setAttribute("username", user);
                // response.sendRedirect("/main.jsp");
                if(remember){
                    Cookie cku=new Cookie("username", user);
                    cku.setMaxAge(3600);
                    response.addCookie(cku);
                    Cookie ckp=new Cookie("password", pass);
                    ckp.setMaxAge(3600);
                    response.addCookie(ckp);
                    JOptionPane.showMessageDialog(null, user+" : "+pass);
                }
                request.getRequestDispatcher("main.jsp").forward(request, response);
                //response.sendRedirect("/main.jsp");
            }
            else{
                session.setAttribute("error", error);
                request.getRequestDispatcher("login.jsp").forward(request, response);
                //response.sendRedirect("/login.jsp");
            }
        }
        catch(Exception e){
            JOptionPane.showMessageDialog(null, e);
            System.out.println(e);
        }
    }
}

以下是我遇到的错误

  

java.lang.IllegalStateException：在提交响应后无法转发