cookie、session和java过滤器结合实现登陆程序

时间:2022-08-31 20:48:57

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:

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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:

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<%@ 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:

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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:

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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:

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<?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:

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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。