Question

我已经使用html创建了一个登录页面，我在其中输入用户名和密码并显示用户名。我创建了一个servlet用于显示用户名，在这里我使用request.getParameter(<fieldName>)来显示用户名。我正在使用Eclipse IDE和Tomcat来部署应用程序。由于该方法返回null，因此无法执行此操作。代码如下：

PageLogin.java

    /**
 * Servlet implementation class PageLogin
 */
@WebServlet("/login")
public class PageLogin extends HttpServlet {
    private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public PageLogin() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        //response.getWriter().append("Served at: ").append(request.getContextPath());
        processRequest(request, response);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        processRequest(request,response);

    }

    public void processRequest(HttpServletRequest request, HttpServletResponse response) throws IOException {
        String user = request.getParameter("username");
        String pass = request.getParameter("password");
        PrintWriter out = response.getWriter();

        System.out.println("username : "+user);
        System.out.println("password : "+pass);

        String htmlResponse = "<html>";
        htmlResponse += "<h2>Username : " + user + "</h2>";
        htmlResponse +="</html>";

        out.println(htmlResponse);
    }

}

index.html

    <!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Login</title>
</head>
<body>

<form action="PageLogin" method="post" >
    Username :<input type="text" name="username"><br>
    Password :<input type="password" name="password"><br>

    <input type="submit" value="Login">

</form>

</body>
</html>

web.xml

    <?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>LoginQ3</display-name>

  <servlet>
  <servlet-name>loginpage</servlet-name>
  <servlet-class>PageLogin</servlet-class>
  </servlet>

  <servlet-mapping>
  <servlet-name>loginpage</servlet-name>
  <url-pattern>/display</url-pattern>
  </servlet-mapping>

  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
</web-app>

当我使用网址

http://localhost:8080/LoginQ3/login

我得到的输出为：

用户名：null

请求getParameter（<fieldname>）返回null

0 个答案: