JavaWeb中的Cookie和Session解讀

更新時間：2023年10月18日 08:55:26 作者：Neo丶

這篇文章主要介紹了JavaWeb中的Cookie和Session解讀,Cookie是servlet發(fā)送到Web瀏覽器的少量信息,該信息由瀏覽器保存,然后發(fā)送回服務(wù)器,一般情況下,Cookie是以鍵值對進(jìn)行表示的,Cookie的值可以唯一地標(biāo)識客戶端,因此Cookie常用于會話管理,需要的朋友可以參考下

Cookie

Cookie是servlet發(fā)送到Web瀏覽器的少量信息，該信息由瀏覽器保存，然后發(fā)送回服務(wù)器。一般情況下，Cookie是以鍵值對進(jìn)行表示的(key-value)，Cookie的值可以唯一地標(biāo)識客戶端，因此Cookie常用于會話管理。servlet通過使用HttpServletResponse#addCookie方法將cookie發(fā)送到瀏覽器，該方法將字段添加到http響應(yīng)頭，以便一次一次地將cookie發(fā)送到瀏覽器，每個Cookie的大小限定為4kb。

創(chuàng)建Cookie

客戶端沒有Cookie -> 服務(wù)器創(chuàng)建Cookie -> 通知客戶端保存Cookie -> 通過響應(yīng)頭Set-Cookie通知客戶端保存Cookie（Set-Cookie：key=value） ->客戶端收到響應(yīng)后發(fā)現(xiàn)set-cookie響應(yīng)頭，查看有沒有Cookie，如果沒有就創(chuàng)建如果有就修改。

package com.pero.servlet.cookie_session;
 
import jakarta.servlet.*;
import jakarta.servlet.http.*;
 
import java.io.IOException;
import java.lang.reflect.Method;
 
public abstract class BaseServlet extends HttpServlet {
 
    protected void add(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 
    }
    protected void delete(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 
    }
    protected void update(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 
    }
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
 
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        String action = request.getParameter("action");
        try {
            Method method = this.getClass().getDeclaredMethod(action, HttpServletRequest.class, HttpServletResponse.class);
            method.invoke(this,request,response);
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

package com.pero.servlet.cookie_session;
 
import jakarta.servlet.*;
import jakarta.servlet.http.*;
 
import java.io.IOException;
 
public class CookieServlet extends BaseServlet {
 
    protected void createCookie(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //創(chuàng)建Cookie
        Cookie cookie = new Cookie("key","value");
        //通知客戶端保存
        response.addCookie(cookie);
        response.getWriter().write("Cookie創(chuàng)建成功");
    }
}

<!DOCTYPE html>
<html lang="en">
<head>
  <meta http-equiv="pragma" content="no-cache" />
  <meta http-equiv="cache-control" content="no-cache" />
  <meta http-equiv="Expires" content="0" />
  <meta http-equiv="content-type" content="text/html;charset=UTF-8">
    <title>Cookie</title>
  <base href="http://localhost:8080/cookie_session/" rel="external nofollow"  rel="external nofollow" >
  <style type="text/css">
    ul li{
      list-style: none;
    }
  </style>
</head>
<body>
  <iframe name="target" width="500" height="500" style="..."></iframe>
  <div style="...">
    <ul>
      <li><a href="cookieServlet?action=createCookie" rel="external nofollow"  target="target">Cookie的創(chuàng)建</a></li>
      <li><a href="cookieServlet?action=getCookie" rel="external nofollow"  target="target">Cookie的獲取</a></li>
      <li><a href="cookieServlet?action=updateCookie" rel="external nofollow"  target="target">Cookie值的修改</a></li>
      <li>Cookie的存活周期</li>
      <li>
        <ul>
          <li><a href="cookieServlet?action=defaultLifeCookie" rel="external nofollow"  target="target">Cookie的默認(rèn)存活時間（會話）</a></li>
          <li><a href="cookieServlet?action=deleteNowCookie" rel="external nofollow"  target="target">Cookie立即刪除</a></li>
          <li><a href="cookieServlet?action=life5Cookie" rel="external nofollow"  target="target">Cookie存活5秒</a></li>
        </ul>
      </li>
      <li><a href="cookieServlet?action=pathCookie" rel="external nofollow"  target="target">Cookie的路徑設(shè)置</a></li>
      <li><a href="" target=" rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" target">Cookie的用戶登錄練習(xí)</a></li>
    </ul>
  </div>
</body>
</html>

服務(wù)器獲取Cookie

客戶端有了Cookie的值 -> 通過請求頭：Cookie：key=value 把Cookie信息發(fā)送給服務(wù)器 -> 服務(wù)器獲取客戶端發(fā)送過來的Cookie只需要一行代碼{request.getCookies()：返回Cookie[]數(shù)組}

package com.pero.servlet.cookie_session;
 
import com.pero.servlet.util.CookieUtil;
import jakarta.servlet.*;
import jakarta.servlet.http.*;
 
import java.io.IOException;
 
public class CookieServlet extends BaseServlet {
 
    protected void getCookie(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Cookie[] cookies = request.getCookies();
 
        for (Cookie cookie : cookies) {
            //getName()獲取Cookie的Key值，getValue()方法獲取Cookie的value值
            response.getWriter().write("Cookie{" + cookie.getName() + ":" + cookie.getValue() + "} <br/>");
        }
        Cookie iWantCookie = CookieUtil.findCookie("key",cookies);
        //如果不等于null意味著找到了Cookie
        if (iWantCookie != null){
            response.getWriter().write("找到了Cookie");
        }
    }
 
    ...
}

package com.pero.servlet.util;
 
import jakarta.servlet.http.Cookie;
 
public class CookieUtil {
    /**
     * 查找指定名稱的Cookie對象
     * @param name
     * @param cookies
     * @return
     */
    public static Cookie findCookie(String name,Cookie[] cookies){
        if (name == null || cookies == null || cookies.length ==0){
            return null;
        }
        for (Cookie cookie : cookies) {
            if (name.equals(cookie.getName())){
                return cookie;
            }
        }
        return null;
    }
}

Cookie值的修改

package com.pero.servlet.cookie_session;
 
import com.pero.servlet.util.CookieUtil;
import jakarta.servlet.*;
import jakarta.servlet.http.*;
 
import java.io.IOException;
 
public class CookieServlet extends BaseServlet {
 
    protected void updateCookie(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //方法一：
        //創(chuàng)建需要修改的同名Cookie對象
        //在構(gòu)造器中同時賦予新的Cookie值
//        Cookie cookie = new Cookie("key","newValue");
        //調(diào)用response.addCookie(Cookie)
//        response.addCookie(cookie);
//        response.getWriter().write("key的Cookie的值已經(jīng)修改");
 
        //方法二
        //查找需要修改的Cookie對象
        Cookie cookie = CookieUtil.findCookie("key",request.getCookies());
        //調(diào)用setValue()方法付于心的Cookie值
        if (cookie != null){
            cookie.setValue("NewCookie");
        }
        //調(diào)用response.addCookie(cookie)通知客戶端保存修改
        response.addCookie(cookie);
    }
    ...
}

Cookie的生命控制

Cookie的生命控制指的是如何管理Cookie什么時候被銷毀（刪除）。setMaxAge()；整數(shù)表示在指定秒數(shù)后過期，負(fù)數(shù)表示瀏覽器一關(guān)Cookie就會被刪除(程序默認(rèn))，0表示立刻刪除Cookie。

package com.pero.servlet.cookie_session;
 
import com.pero.servlet.util.CookieUtil;
import jakarta.servlet.*;
import jakarta.servlet.http.*;
 
import java.io.IOException;
 
public class CookieServlet extends BaseServlet {
 
    protected void life5Cookie(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Cookie cookie = new Cookie("life5","life5");
        cookie.setMaxAge(5);    //設(shè)置Cookie5秒后刪除
        response.addCookie(cookie);
        response.getWriter().write("創(chuàng)建了5秒鐘的Cookie");
    }
    protected void deleteNowCookie(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //查找需要刪除的Cookie
        Cookie cookie = CookieUtil.findCookie("key",request.getCookies());
        if (cookie != null){
            //設(shè)置cookie.setMaxAge(0);立刻銷毀Cookie
            cookie.setMaxAge(0);
            //response.addCookie();瀏覽器保存
            response.addCookie(cookie);
            response.getWriter().write("key的Cookie已經(jīng)被刪除");
        }
    }
    protected void defaultLifeCookie(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Cookie cookie = new Cookie("defaultLife","defaultLife");
        cookie.setMaxAge(-1);   //設(shè)置存活時間為瀏覽器退出后Cookie被銷毀
        response.addCookie(cookie);
    }
    ...
}

Cookie有效路徑Path的設(shè)置

Cookie的path屬性可以有效的過濾那些Cookie可以發(fā)送給服務(wù)器那些不發(fā)送，path屬性是通過請求的地址來進(jìn)行過濾。

package com.pero.servlet.cookie_session;
 
import com.pero.servlet.util.CookieUtil;
import jakarta.servlet.*;
import jakarta.servlet.http.*;
 
import java.io.IOException;
 
public class CookieServlet extends BaseServlet {
 
    protected void pathCookie(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Cookie cookie = new Cookie("path","path");
        //getContextPath()得到工程路徑
        cookie.setPath(request.getContextPath() + "/file");
        response.addCookie(cookie);
        response.getWriter().write("創(chuàng)建了一個帶有Path路徑的Cookie");
    }
    ...
}

Cookie練習(xí)免用戶名登陸

第一次登錄時：客戶端（瀏覽器）第一次訪問，服務(wù)器返回給客戶端登陸頁面，填寫用戶名和密碼后提交給服務(wù)器，服務(wù)器獲取用戶名和密碼，判斷用戶名和密碼是否正確，正確允許登錄，錯誤不允許登錄，把用戶名保存為Cookie發(fā)送給客戶端，瀏覽器有了用戶名和Cookie信息；

第二次登陸時：客戶端（瀏覽器）第二次訪問服務(wù)器會把Cookie信息發(fā)給服務(wù)器，服務(wù)器返回給客戶端帶用戶名的登錄界面。

package com.pero.servlet.cookie_session;
 
import jakarta.servlet.*;
import jakarta.servlet.http.*;
 
import java.io.IOException;
 
public class LoginServlet extends HttpServlet {
    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        if ("root".equals(username) && "root".equals(password)){
            //登陸成功
            Cookie cookie = new Cookie("username", username);
            cookie.setMaxAge(60*60*24*7);   //cookie一周內(nèi)有效
            response.addCookie(cookie);
            System.out.println("登陸成功");
        }else {
            System.out.println("登陸失敗");
        }
    }
 
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
 
    }
}

<%--
  Created by IntelliJ IDEA.
  User: Administrator
  Date: 2023/3/16
  Time: 18:35
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <form action="http://localhost:8080/cookie_session/loginServlet" method="get">
        用戶名：<input type="text" name="username" value="${cookie.username.value}">

        密  碼：<input type="password" name="password">

        <input type="submit" value="登錄">
    </form>
</body>
</html>

Session

Session是一個接口（HttpSession），Session是會話，用來維護一個客戶端和服務(wù)器之間關(guān)聯(lián)的一種技術(shù)，每個客戶端都有自己的一個Session會話，Session會話中經(jīng)常用來保存用戶登錄之后的信息。

創(chuàng)建Session和獲取

request.getSession()：第一次調(diào)用是創(chuàng)建Session會話，之后都是調(diào)用，獲取前面創(chuàng)建好的Session會話對象；
isNew()：判斷是不是新創(chuàng)建出來的Session，true表示新創(chuàng)建，false表示獲取之前創(chuàng)建的；
getId()：得到Session會話的id值，每一個會話都有一個id值，這個id值是唯一的。

package com.pero.servlet.cookie_session;
 
import jakarta.servlet.*;
import jakarta.servlet.http.*;
 
import java.io.IOException;
 
public class SessionServlet extends BaseServlet {
    protected void createOrGetSession(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //創(chuàng)建和獲取Session會話對象
        HttpSession session = request.getSession();
        //判斷當(dāng)前Session會話是否是新創(chuàng)建出來的
        boolean isNew = session.isNew();
        //獲取Session會話的唯一標(biāo)識
        String id = session.getId();
 
        response.getWriter().write("得到的Session的ID：" + id + " <br/>");
        response.getWriter().write("Session是否為新創(chuàng)建的：" + isNew + " <br/>");
    }
 
}

<!DOCTYPE html>
<html lang="en">
<head>
    <meta http-equiv="pragma" content="no-cache"/>
    <meta http-equiv="cache-control" content="no-cache"/>
    <meta http-equiv="Expires" content="0"/>
    <meta http-equiv="content-type" content="text/html;charset=UTF-8">
    <title>Session</title>
    <base href="http://localhost:8080/cookie_session/" rel="external nofollow"  rel="external nofollow" >
    <style type="text/css">
        ul li {
            list-style: none;
        }
    </style>
</head>
<body>
<iframe name="target" width="500" height="500" style="..."></iframe>
<div style="...">
    <ul>
        <li><a href="sessionServlet?action=createOrGetSession" rel="external nofollow"  target="target">Session的創(chuàng)建和獲取</a></li>
        <li><a href="" target=" rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" target">Session域數(shù)據(jù)的存儲</a></li>
        <li><a href="" target=" rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" target">Session域數(shù)據(jù)的獲取</a></li>
        <li>Session的存活周期</li>
        <li>
            <ul>
                <li><a href="" target=" rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" target">Session默認(rèn)超時配置</a></li>
                <li><a href="" target=" rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" target">Session5秒超時銷毀</a></li>
                <li><a href="" target=" rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" target">Session立刻銷毀</a></li>
            </ul>
        </li>
        <li><a href="" target=" rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow"  rel="external nofollow" target">瀏覽器和Session綁定的原理</a></li>
    </ul>
</div>
</body>
</html>

Session域中數(shù)據(jù)的存取

package com.pero.servlet.cookie_session;
 
import jakarta.servlet.*;
import jakarta.servlet.http.*;
 
import java.io.IOException;
 
public class SessionServlet extends BaseServlet {
 
    protected void getAttributeSession(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        Object attribute = session.getAttribute("key");
        response.getWriter().write("從Session中獲取key的值為：" + attribute);
    }
 
    protected void setAttributeSession(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        session.setAttribute("key","value");
        response.getWriter().write("已經(jīng)向Session中存儲值");
 
    }
 
    ...
}

Session生命周期

Session超時是指客戶端兩次請求的最大間隔時間。

public void setMaxInactiveInterval(int interval)：設(shè)置Session超時時間（以秒為單位），超過指定時長Session會被銷毀，值為正數(shù)的時候，設(shè)定Session的超市時長，值為負(fù)數(shù)的時候，Session永不超時；
public void invalidate()：讓Session會話立刻超時無效；
public int getMaxInactiveInterval()：獲取Session的超時時間；

Session的默認(rèn)超時時長為：Session的默認(rèn)超時時長為1800秒。

package com.pero.servlet.cookie_session;
 
import jakarta.servlet.*;
import jakarta.servlet.http.*;
 
import java.io.IOException;
 
public class SessionServlet extends BaseServlet {
 
    protected void defaultLife(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        int maxInactiveInterval = session.getMaxInactiveInterval();
        response.getWriter().write("Session的默認(rèn)超時時長為" + maxInactiveInterval + "秒");
    }
    ...
}

如果調(diào)整web工程的超時時長，可以在web.xml中進(jìn)行配置。

<!-- 表示當(dāng)前web工程創(chuàng)建出來的所有Session默認(rèn)是20分鐘超時時長 -->
    <session-config>
        <session-timeout>10</session-timeout>
    </session-config>

也可以通過setMaxInactiveInterval(int interval)設(shè)置Session超時時間

package com.pero.servlet.cookie_session;
 
import jakarta.servlet.*;
import jakarta.servlet.http.*;
 
import java.io.IOException;
 
public class SessionServlet extends BaseServlet {
 
    protected void life5Session(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        //設(shè)置當(dāng)前Session5秒后超時
        session.setMaxInactiveInterval(5);
        response.getWriter().write("當(dāng)前Session已經(jīng)設(shè)置為5秒后超時");
    }
    ...
}

設(shè)置Session立刻超時

package com.pero.servlet.cookie_session;
 
import jakarta.servlet.*;
import jakarta.servlet.http.*;
 
import java.io.IOException;
 
public class SessionServlet extends BaseServlet {
 
    protected void shutDownSession(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        HttpSession session = request.getSession();
        //設(shè)置當(dāng)前Session立刻超時
        session.invalidate();
        response.getWriter().write("當(dāng)前Session立刻超時關(guān)閉");
    }
    ...
}