Question

我在JSP中创建 loginpage.jsp ：

<form method="post" action="login">
    <input type="text" name="username">
    <input type="password" name=password">
    <input type="submit" value="Send">
    <div id="authFail"></div>                                                          </form>

如果用户登录失败，服务器将调度员返回登录页面并显示文本“登录失败”。然后，我创建一个servlet作为登录控制器：

@Override
public void doPost(HttpServletRequest request, HttpSevletResponse response
    throws IOException, ServletException {
    response.setContentType("text/html");
    PrintWriter out = response.getWriter();
    String username = request.getParameter("name");
    String password = request.getParameter("password");    
    if (username.equals("admin") && password.equals("root")) {
         request.getRequestDispatcher("homepage.jsp").include(request, response);
     } else {
         request.getRequestDispatcher("loginpage.jsp").include(request, response);
         out.print("document.getElementById(\"authFail\").innerHTML=\"Login Failed!!!\"");
     }
}

问题： 当用户登录失败并将其发送回登录页面但未显示文本“登录失败!!! 我已经在web.xml中将我的servlet配置为url模式“login”。

Answer 1

嗨，你可以这样做

@Override
public void doPost(HttpServletRequest request, HttpSevletResponse response
    throws IOException, ServletException {
    response.setContentType("text/html");
    PrintWriter out = response.getWriter();
    String username = request.getParameter("name");
    String password = request.getParameter("password");

    if (username.equals("admin") && password.equals("root")) {
         request.getRequestDispatcher("homepage.jsp").include(request, response);
     } else {
            request.setAttribute("errorMessage", "Login Failed");

         request.getRequestDispatcher("loginpage.jsp").include(request, response);
     }
}

并以表格

<form method="post" action="login">
    <div>${errorMessage}</div>
    <input type="text" name="username">
    <input type="password" name=password">
    <input type="submit" value="Send">
    <div id="authFail"></div>

为了更好的结果，请使用JSTL

<c:if test="${not empty errorMessage}">
   <c:out value="${errorMessage}"/>
</c:if>

要使用JSTL，您必须将此代码添加到jsp文件

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<pre class="prettyprint">

在servlet调度程序之后设置innerHTML

1 个答案: