Question

我想在登录和密码错误时显示错误消息，我尝试了这个尝试，但它没有用，谢谢。

的index.html

<body>
<form action="Serv">
<input type="text" name="log">
<input type="password" name="pwd">
<input type="submit" value="send">
</form>
</body>

Serv.java

 response.setContentType("text/html;charset=UTF-8");
 PrintWriter out = response.getWriter(); 
 String u =request.getParameter("log");
 String p =request.getParameter("pwd");
 if(u != "admin"  && p!= "admin"){
 String someMessage = "Error !";
 getServletContext().getRequestDispatcher("/index.html").forward(request, response); 
 out.println("<html><head>");

out.println("<script type=\"text/javascript");
   out.println("alert("+ someMessage +");</script>");
out.println("</head><body></body></html>");
}

Answer 1

尽可能在里面使用单引号，试试这个：

String someMessage = "Error !";
out.println("<script type='text/javascript'>");
out.println("alert(" + "'" + someMessage + "'" + ");</script>");
out.println("</head><body></body></html>");

Answer 2

看起来您没有关闭引号或脚本标记，添加结束引号/尖括号：

out.println("<script type=\"text/javascript\">");

如何从servlet显示错误消息？

2 个答案: