创建MyFilter1类过滤器,对于未登陆用户(如果session对象中包含用户名就认为已登录)进行过滤跳转到登录页面

XML的配置

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>chapter1201</display-name>
  <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>
 	<filter>
		<filter-name>MyFilter1</filter-name>
		<filter-class>cn.itheima.MyFilter1</filter-class>
	</filter>
	<filter-mapping>
		<filter-name>MyFilter1</filter-name>
		<url-pattern>/OtherServlet斜杠*</url-pattern>
	</filter-mapping>
	<servlet>
		<servlet-name>LoginServlet</servlet-name>
		<servlet-class>cn.itheima.LoginServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>LoginServlet</servlet-name>
		<url-pattern>/UserServlet/Login</url-pattern>
	</servlet-mapping>
	<servlet>
		<servlet-name>OrderServlet</servlet-name>
		<servlet-class>cn.itheima.OrderServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>OrderServlet</servlet-name>
		<url-pattern>/OtherServlet/order</url-pattern>
	</servlet-mapping>
</web-app>

index.jsp代码如下

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
您好,请<a href="/chapter1201/UserServlet/Login">登录</a>&nbsp;&nbsp;&nbsp;<a href="/chapter1201/OtherServlet/order">我的订单</a>
		欢迎访问本网站!!!
</body>
</html>

login.jsp代码如下:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<form name="reg" action="#" method="post">
		用户名:  <input name="username" type="text" /><br /> 
		密 码:   <input name=password type="text" /><br /> 
		<input type="submit" value="登录" id="bt" />
	</form>
</body>
</html>

LoginServlet代码如下

package cn.itheima;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class LoginServlet
 */
public class LoginServlet extends HttpServlet {
     
	private static final long serialVersionUID = 1L;

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
     
		req.getRequestDispatcher("/login.jsp").forward(req, resp);
	}
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
     
		doGet(req, resp);
	}

}

OrderServlet代码如下

package cn.itheima;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class OrderServlet
 */
public class OrderServlet extends HttpServlet {
     
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public OrderServlet() {
     
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
     
		req.getRequestDispatcher("/order.jsp").forward(req, resp);
	}
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
     
		doGet(req, resp);
	}


}

MyFilter1类过滤器

package cn.itheima;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet Filter implementation class MyFilter1
 */
public class MyFilter1 implements Filter {
     

    /**
     * Default constructor. 
     */
    public MyFilter1() {
     
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see Filter#destroy()
	 */
	public void destroy() {
     
		// TODO Auto-generated method stub
	}

	/**
	 * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
	 */
	public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException {
     
		HttpServletRequest request = (HttpServletRequest) req;
		request.setCharacterEncoding("utf-8");
		HttpServletResponse response = (HttpServletResponse) resp;
		response.setContentType("text/html;charset=utf-8");
		
		
		Object user =  request.getSession().getAttribute("user");
		if(user==null){
     
			//session没有对象就跳转到登录页面
			req.getRequestDispatcher("/login.jsp").forward(req, resp);
		}else{
     
			chain.doFilter(request, response);
		}
	}

	/**
	 * @see Filter#init(FilterConfig)
	 */
	public void init(FilterConfig fConfig) throws ServletException {
     
		// TODO Auto-generated method stub
	}

}

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