java代码实现自动登录功能

通常我们登录某网站，会有选择保存几天，或者是几个星期不用登录，之后输入该网站地址无需登录直接进入主页面，那么这就叫做自动登录，怎么实现呢，下面我以一个小例子来演示一下

登录页面：login.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<html>

  <head>

  </head>

  <body>

  <form action="login.do">

    用户名：<input type="text" name="username" ><br/>

    密    码：<input type="text" name="password" ><br/>

    <input type="submit" value="登录" /><select name="saveTime">

    <option value="366">一年</option>

    <option value="183">半年</option>

     <option value="30">一个月</option>

     <option value="7">一周</option>

    </select>

  </form>

  </body>

</html>

那么从上面可看到可选择保存自动登录的期限，可以是一年，半年，一个月，一周，当然这都是以天为单位的

服务类：LoginService

package com.login.servlet;

public class LoginService {

	public static boolean login(String username, String password) {

		if ("admin".equals(username) && "123456".equals(password)) {

			return true;

		} else {

			return false;

		}

	}

}

业务处理servlet:LoginServlet

package com.login.servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.Cookie;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class LoginServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

        this.doPost(request, response);

	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)

			throws ServletException, IOException {

		 String username=request.getParameter("username");

		   String password=request.getParameter("password");

		   String savetime=request.getParameter("saveTime");

		   if(LoginService.login(username, password)){

			   if(null!=savetime&&!savetime.isEmpty()){

				   int saveTime=Integer.parseInt(savetime);//这里接受的表单值为天来计算的

				   int seconds=saveTime*24*60*60;

				   Cookie cookie = new Cookie("user", username+"=="+password);

				   cookie.setMaxAge(seconds);

				   response.addCookie(cookie);

			   }

			   request.setAttribute("username",username);

			   request.getRequestDispatcher("/main.jsp").forward(request,response);

		   }else{

			   request.getRequestDispatcher("/index.jsp").forward(request,response);

		   }

	}

}

看清上面处理Cookie的方式步骤：其实这是为第一次登录该网站时【前提是选择了保存自动登录期限时间】处理Cookie,只要这一步处理成功，以后都无需经过这个Servlet因为我们接下来要在请求到达前，从Cookie中取出我们的用户名和密码，这样的话就需要一个过滤器了

package com.login.servlet;

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.Cookie;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class IndexFilter implements Filter {

	public void destroy() {

		// TODO Auto-generated method stub

	}

	public void doFilter(ServletRequest arg0, ServletResponse arg1,

			FilterChain arg2) throws IOException, ServletException {

		HttpServletRequest request = (HttpServletRequest) arg0;

		HttpServletResponse response = (HttpServletResponse) arg1;

		Cookie[] cookies = request.getCookies();

		String[] cooks = null;

		String username = null;

		String password = null;

		if (cookies != null) {

			for (Cookie coo : cookies) {

				String aa = coo.getValue();

				cooks = aa.split("==");

				if (cooks.length == 2) {

					username = cooks[0];

					password = cooks[1];

				}

			}

		}

		if (LoginService.login(username, password)) {

			request.getSession().setAttribute("username",username);

			response.sendRedirect("main.jsp");

			//request.getRequestDispatcher("/main.jsp").forward(request, response);

		}else{

			arg2.doFilter(request,response );

		}

	}

	public void init(FilterConfig arg0) throws ServletException {

		// TODO Auto-generated method stub

	}

}

我这里所说的请求到达之前，不是指的某个路径匹配的servlet而是指的就是在输入网址到达登录页面前就要进行自动登录的处理，那么web.xml中应该怎么配置呢

<?xml version="1.0" encoding="UTF-8"?>

<web-app version="2.5"

	xmlns="http://java.sun.com/xml/ns/javaee"

	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee

	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

  <filter>

  <filter-name>loginFilter</filter-name>

  <filter-class>com.login.servlet.IndexFilter</filter-class>

  </filter>

  <filter-mapping>

  <filter-name>loginFilter</filter-name>

  <url-pattern>/index.jsp</url-pattern>

  </filter-mapping>

  <servlet>

    <servlet-name>LoginServlet</servlet-name>

    <servlet-class>com.login.servlet.LoginServlet</servlet-class>

  </servlet>

  <servlet-mapping>

    <servlet-name>LoginServlet</servlet-name>

    <url-pattern>/login.do</url-pattern>

  </servlet-mapping>

  <welcome-file-list>

    <welcome-file>login.jsp</welcome-file>

  </welcome-file-list>

</web-app>

看见了没有，上面的filter匹配路径只是针对一个页面，与通常写/*匹配所有请求到达之前是不一样的写法哦

主页面：main.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>

<html>

  <head>

     <title>My JSP 'maiin.jsp' starting page</title>

  </head>

  <body>

    登录成功，欢迎${username}的到来

  </body>

</html>

输入地址：http://localhost:8080/WebApp/login.jsp，出现登录页面

然后输入：admin,123456 ，选择一个保存日期

这样第一次登录成功之后，是经由LoginServlet处理了，由于选择了日期，所以Cookie中保存了用户信息，所以之后再输入同样地址后，不会出现登录页面，就不再经过LoginServlet处理【因为LoginServlet处理的是登陆页面上登录按钮请求的】，而直接提前交由IndexFilter处理，直接进入主页面，明白了么

巴特西

java代码实现自动登录功能

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