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cookie、session和java过滤器结合实现登陆程序

程序员文章站 2024-03-12 10:04:38
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 { 
 
  } 
 
} 

以上就是本文的全部内容,希望对大家学习java程序设计有所帮助。