9.过滤器、监听器常见应用

监听器在GUI中常用

过滤器demo：用户登录之后才能进入主页！用户注销后就不能进入主页了！

用户登录之后，向Sesison中放入用户的数据
进入主页的时候要判断用户是否已经登录；要求：在过滤器中实现！

Login.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>登录</h1>
    <form action="/servlet/login" method="post">
        <input type="text" name="username">
        <input type="submit">
    </form>
</body>
</html>

success.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<%--<%--%>
<%--    Object userSession = request.getSession().getAttribute("USER_SESSION");--%>
<%--    if(userSession==null){--%>
<%--//        pageContext.forward("/Login.jsp");--%>
<%--        response.sendRedirect("/Login.jsp");--%>
<%--    }--%>
<%--%>--%>

<h1>success</h1>
<h3><a href="/servlet/logout">注销</a> </h3>
</body>
</html>

error.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>没有权限</h1>
<a href="/Login.jsp">返回登录页</a>
</body>
</html>

SysFilter.java（拦截器）

package com.lxw.filter;

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 request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest request1 = (HttpServletRequest) request;
        HttpServletResponse response1 = (HttpServletResponse) response;

        if (request1.getSession().getAttribute("USER_SESSION")==null) {
            response1.sendRedirect("/error.jsp");
        }

        chain.doFilter(request1,response1);
    }

    @Override
    public void destroy() {

    }
}

LoginServlet.java

package com.lxw.servlet;

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")) {
            System.out.println("登陆成功");
            req.getSession().setAttribute("USER_SESSION",req.getSession().getId());
            resp.sendRedirect("/sys/success.jsp");

        }else{
            System.out.println("登陆失败");
            resp.sendRedirect("/error.jsp");

        }
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

LogOutServlet.java

package com.lxw.servlet;

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("USER_SESSION");
        if (user_session!=null) {
            req.getSession().removeAttribute("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);
    }
}

web.xml

<servlet>
        <servlet-name>LoginServlet</servlet-name>
        <servlet-class>com.lxw.servlet.LoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>LoginServlet</servlet-name>
        <url-pattern>/servlet/login</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>LogoutServlet</servlet-name>
        <servlet-class>com.lxw.servlet.LogoutServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>LogoutServlet</servlet-name>
        <url-pattern>/servlet/logout</url-pattern>
    </servlet-mapping>

    <filter>
        <filter-name>SysFilter</filter-name>
        <filter-class>com.lxw.filter.SysFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>SysFilter</filter-name>
        <url-pattern>/sys/*</url-pattern><!-- 拦截访问/sys/*下的所有请求-->
    </filter-mapping>

目录CONTENT

9.过滤器、监听器常见应用

9.过滤器、监听器常见应用

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