1、新建login.jsp 登录界面 响应的路径
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Login</title>
</head>
<body>
<h1>登录界面</h1>
<hr>
<form action="/servlet/login" method="post">
<input type="text" name="username">
<input type="submit">
</form>
</body>
</html>2、写对应的loginServlet
package com.feijian.servlet;
import com.feijian.util.constant;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class LoginServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String username = req.getParameter("username");
if (username.equals("admin")){
req.getSession().setAttribute(constant.USER_SESSION,req.getSession().getId());
resp.sendRedirect("/sys/success.jsp");
}else {
resp.sendRedirect("/sys/error.jsp");
}
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}3、设置sucess.jsp，和error.jsp页面。
<%--
Created by IntelliJ IDEA.
User: Administrator
Date: 2023/4/11
Time: 20:02
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>主页</title>
</head>
<body>
<%--<%--%>
<%-- Object userName = request.getSession().getAttribute("USER_NAME");--%>
<%-- if (userName==null){--%>
<%-- response.sendRedirect("/login.jsp");--%>
<%-- }--%>
<%--%>--%>
<hr>
<br>
<h1>登录成功！</h1> <br>
<p><a href="/servlet/logout">注销</a></p>
<hr>
<br>
</body>
</html><%--
Created by IntelliJ IDEA.
User: Administrator
Date: 2023/4/11
Time: 20:03
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>错误界面</title>
</head>
<body>
<h3><span style="color: red">错误页面，登录不成功！</span></h3>
<a href="/login.jsp">返回登录界面</a>
</body>
</html>4、再写一个logoutServlet
package com.feijian.servlet;
import com.feijian.util.constant;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class LogoutServlet extends HttpServlet {
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
Object user_session = req.getSession().getAttribute(constant.USER_SESSION);
if (user_session!=null){
req.getSession().removeAttribute(constant.USER_SESSION);
resp.sendRedirect("/login.jsp");
}else {
resp.sendRedirect("/login.jsp");
}
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}5、写一个Filter类
package com.feijian.filter;
import com.feijian.util.constant;
import javax.servlet.*;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
public class sysFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
}
@Override
public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) req;
HttpServletResponse response = (HttpServletResponse) resp;
if (request.getSession().getAttribute(constant.USER_SESSION)==null){
response.sendRedirect("/error.jsp");
}
chain.doFilter(req,resp);
}
@Override
public void destroy() {
}
}6、在web.xml中注册 三个类，loginServlet, logoutServlet, filter 类 并在映射路径上和前端页面上的一致。
注意：传入的值建议写入Session,这样取值即使页面跳转，只要浏览器不关闭就一直存在，不会丢失，如果用request 在重定向的情况下打开新页面就无法页面间传值。
标签：11,Javaweb,resp,req,HttpServletResponse,filter,import,servlet,javax From： https://www.cnblogs.com/RUI2022/p/17307948.html