JSP访问Controller返回对话框

    //注意Controller方法无明确返回值 void
    response.setContentType("text/html; charset=UTF-8"); //转码
    PrintWriter out = response.getWriter();
    out.flush();
    out.println("<script>");
    out.println("alert('此用户不存在!');");
    out.println("history.back();");
    out.println("</script>");
    return;