cookie、session和java过滤器结合实现登陆程序
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2024-03-11 16:28:07
cookie、session和过滤器通常都是用在web应用中,cookie和session用来保存一定的数据,过滤器filter则是在浏览器发出请求之后,而后台执行特定的请...
cookie、session和过滤器通常都是用在web应用中,cookie和session用来保存一定的数据,过滤器filter则是在浏览器发出请求之后,而后台执行特定的请求之前发生一定的作用。之所以把这三个放一起,是因为有很多时候都会是把他们结合在一起使用,例如有些登陆程序。
cookie是浏览器的机制,session是服务器的机制,但是实际上cookie也是由服务器生成的,之后返回给浏览器的,并不是浏览器本身生成。当浏览器发送某个请求时,如果拥有有效的cookie则会把这个cookie带在一起。
之所有会有cookie的使用,是因为http协议原本是无状态协议,也就是说通过http协议本身,服务器不能判断浏览器是否之前访问过。
filter和servlet的写法相似,编写相关代码的时候需要实现filter接口并重写相关的方法,通常更改较多的是dofilter方法。filter代码写好以后如果需要发生效用,需要像配置servlet一样在web.xml中 进行一定的配置。
以下是一个简单的结合cookie、session、servlet和filter的登陆示例代码:
定义一个用户实体类,充当数据库数据,这里使用单例模式,保证只存在一个实例对象:
package models; /** * 用户信息实体类 * * @author tuzongxun123 * */ public class usermodel { private string username; private string password; // 单例模式,保证只有一个用户对象实例 public static usermodel getinstance() { usermodel user = new usermodel("zhangsan", "123456"); return user; } private usermodel(string username, string pasword) { this.username = username; this.password = pasword; } public string getusername() { return username; } public string getpassword() { return password; } }
用户登陆输入信息index.jsp界面,在form表单的action中使用jsp的特性获得项目路径:
<%@ page language="java" import="java.util.*" 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>cookieandfiltertest</title> </head> <body> <form action="<%=request.getcontextpath() %>/loginservlet" method="post"> username:<input type="text" name="username" /></br> password:<input type="password" name="password" /></br> <input type="submit" value="login"/> </form> </body> </html>
对应的后台servlet:
package servlettest; 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; import javax.servlet.http.httpsession; import models.usermodel; public class loginservlet extends httpservlet { @override protected void doget(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception { this.dopost(req, resp); } @override protected void dopost(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception { string username = req.getparameter("username"); string password = req.getparameter("password"); // 模拟数据库数据 usermodel user = usermodel.getinstance(); string dbusername = user.getusername(); string dbpassword = user.getpassword(); if (dbusername.equals(username) && dbpassword.equals(password)) { // 用户名和密码都匹配,证明登陆成功,设置session和cookie httpsession session = req.getsession(); session.setattribute("username", username); session.setattribute("password", password); cookie cookie = new cookie("username", username); cookie cookie2 = new cookie("password", password); // 设置cookie的存储时长 cookie.setmaxage(60); cookie2.setmaxage(60); // 把cookie发送给浏览器 resp.addcookie(cookie); resp.addcookie(cookie2); // 转发请求到用户列表 req.getrequestdispatcher("/userlist").forward(req, resp); } else { // 转发请求到登陆页面 req.getrequestdispatcher("index.jsp").forward(req, resp); } ; } }
上边登陆后跳转的请求:
package servlettest; import java.io.ioexception; import javax.servlet.servletexception; import javax.servlet.http.httpservlet; import javax.servlet.http.httpservletrequest; import javax.servlet.http.httpservletresponse; import models.usermodel; public class userlistservlet extends httpservlet { @override protected void doget(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception { this.dopost(req, resp); } @override protected void dopost(httpservletrequest req, httpservletresponse resp) throws servletexception, ioexception { usermodel user = usermodel.getinstance(); //在浏览器中打印出用户列表书数据 resp.getwriter().write( "username:" + user.getusername() + "," + "password:" + user.getpassword()); } }
项目web.xml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" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" 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"> <!-- 访问时的项目名称 --> <display-name>cookieandfiltertest</display-name> <!-- servlet配置 --> <servlet> <servlet-name>login</servlet-name> <servlet-class>servlettest.loginservlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>login</servlet-name> <url-pattern>/loginservlet</url-pattern> </servlet-mapping> <servlet> <servlet-name>userlist</servlet-name> <servlet-class>servlettest.userlistservlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>userlist</servlet-name> <url-pattern>/userlist</url-pattern> </servlet-mapping> <!-- 过滤器设置,浏览其发送请求后首先会走这里 --> <filter> <filter-name>loginfilter</filter-name> <filter-class>filtertest.filtertest</filter-class> </filter> <filter-mapping> <filter-name>loginfilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <!-- 输入项目名访问的默认页面 --> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>
java过滤器代码:
package filtertest; 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; import models.usermodel; public class filtertest implements filter { @override public void destroy() { } @override public void dofilter(servletrequest request, servletresponse response, filterchain chain) throws ioexception, servletexception { // 登陆请求、初始请求直接放行 httpservletrequest req = (httpservletrequest) request; httpservletresponse resp = (httpservletresponse) response; string uri = req.getrequesturi(); if ("/cookieandfiltertest/loginservlet".equals(uri) || "/cookieandfiltertest/".equals(uri)) { // 放行 chain.dofilter(request, response); return; } // 不是登陆请求的话,判断是否有cookie cookie[] cookies = req.getcookies(); if (cookies != null && cookies.length > 0) { string username = null; string password = null; // 判断cookie中的用户名和密码是否和数据库中的一致,如果一致则放行,否则转发请求到登陆页面 for (cookie cookie : cookies) { if ("username".equals(cookie.getname())) { username = cookie.getvalue(); } if ("password".equals(cookie.getname())) { password = cookie.getvalue(); } } usermodel user = usermodel.getinstance(); if (user.getusername().equals(username) && user.getpassword().equals(password)) { chain.dofilter(request, response); return; } else { // 重定向到登陆界面 req.getrequestdispatcher("/index.jsp").forward(req, resp); return; } } else { req.getrequestdispatcher("/index.jsp").forward(req, resp); return; } } @override public void init(filterconfig arg0) throws servletexception { } }
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