一篇文章搞懂Cookie

「爱情、让人受尽委屈。」 2024-03-27 15:52 15阅读 0赞

**目录**

1 什么是Cookie

2 创建Cookie

3 浏览器查看Cookie

3.1 浏览器查看Cookie的第一种方式

3.2 浏览器查看Cookie的第二种方式

4 获取Cookie

5 修改Cookie

6 Cookie编码与解码

6.1 创建带中文Cookie

6.2 读取带中文Cookie

6.3 获取中文Cookie请求效果

6.4 解决创建和获取中文Cookie

7 Cookie优点和缺点

7.1 Cookie优点

7.2 Cookie缺点

--------------------

### 1 什么是Cookie ###

Cookie是在浏览器访问Web服务器的某个资源时，由Web服务器在HTTP响应消息头中附带传送给浏览器的一小段数据。

一旦Web浏览器保存了某个Cookie，那么它在以后每次访问该Web服务器时，都应在HTTP请求头中将这个Cookie回传给Web服务器。

一个Cookie主要有标识该信息的名称（name）和值（value）组成。

![5ce31b7c0a8249308552075245f968c6.png][]

### 2 创建Cookie ###

//设置Cookie
     Cookie cookie = new Cookie("username", "zhangsan");
    
    /*
    *设置Cookie存活时间，在浏览器内存中的保存时间，单位为秒，
    *   正数：将Cookie写入浏览器所在电脑的硬盘，持久化存储。到时间自动删除
    *   负数：默认值，Cookie在当前浏览器内存中，当浏览器关闭，则Cookie被销毁
    *   零：删除对应Cookie
    */
    cookie.setMaxAge(60);
    
    //设置Cookie的访问路径
    cookie.setPath("/webProject05_war_exploded/GetCookieValueServlet01");
    
    //发送Cookie到客户端
    response.addCookie(cookie);

### 3 浏览器查看Cookie ###

#### 3.1 浏览器查看Cookie的第一种方式 ####

![1d43c3579bff45bf8370f743ea99a487.png][]

#### 3.2 浏览器查看Cookie的第二种方式 ####

![c9faaf8e73c144a09eb36cf039413632.png][]

### 4 获取Cookie ###

//获取所有Cookie
    Cookie[] cookies = request.getCookies();
    
    //遍历数组,获取所有的Cookie
    for (Cookie cookie : cookies) {
        System.out.println(cookie.getName() + "-" + cookie.getValue());
    }
    
    System.out.println("----------------------------------------");
    
    //遍历数组，获取指定的Cookie
    for (Cookie cookie : cookies) {
       if (cookie.getName().equals("username")) {
          System.out.println(cookie.getName() + "-" + cookie.getValue());
       }
    }

### 5 修改Cookie ###

只需要保证Cookie的名称和路径一致即可修改

注意：如果改变cookie的name和有效路径，会新建cookie,而改变cookie值、有效期会覆盖原有cookie

//设置Cookie,如果改变cookie的name和有效路径，会新建cookie,而改变cookie值、有效期会覆盖原有cookie
    Cookie cookie = new Cookie("username", "lisi");
    
    /*
    *设置Cookie存活时间，在浏览器内存中的保存时间，单位为秒，
    *   正数：将Cookie写入浏览器所在电脑的硬盘，持久化存储。到时间自动删除
    *   负数：默认值，Cookie在当前浏览器内存中，当浏览器关闭，则Cookie被销毁
    *   零：删除对应Cookie
    */
    cookie.setMaxAge(30);
    
    //设置Cookie的访问路径
     cookie.setPath("/webProject09_war_exploded/GetCookieValueServlet01");
    
    //发送Cookie到客户端
    response.addCookie(cookie);

### 6 Cookie编码与解码 ###

Cookie默认不支持中文，只能包含ASCII字符，所以Cookie需要对Unicode字符进行编码，否则会出现乱码

*  编码可以使用java.net.URLEncoder类的encode(String str,String encoding)方法
 *  解码可以使用java.net.URLDecoder类的decode(String str,String encoding)方法

#### 6.1 创建带中文Cookie ####

package com.cxyzxc.www.servlet01;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.Cookie;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    @WebServlet(name = "CookieServlet03", value = "/CookieServlet03")
    public class CookieServlet03 extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //设置请求参数的编码格式，这种方式对get请求方式无效
            request.setCharacterEncoding("UTF-8");
            //设置响应编码格式为UTF-8
            response.setContentType("text/html;charset=UTF-8");
    
            //Cookie默认不支持中文，只能包含ASCII字符，所以Cookie需要对Unicode字符进行编码，否则会出现乱码
            Cookie cookie = new Cookie("姓名", "张三");
    
            //设置Cookie的访问路径
            cookie.setPath("/webProject09_war_exploded/GetCookieValueServlet03");
    
            //发送Cookie到客户端
            response.addCookie(cookie);
        }
    
        @Override
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            doGet(request, response);
        }
    }

#### 6.2 读取带中文Cookie ####

package com.cxyzxc.www.servlet01;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.Cookie;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    
    @WebServlet(name = "GetCookieValueServlet03", value = "/GetCookieValueServlet03")
    public class GetCookieValueServlet03 extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //设置请求参数的编码格式，这种方式对get请求方式无效
            request.setCharacterEncoding("UTF-8");
            //设置响应编码格式为UTF-8
            response.setContentType("text/html;charset=UTF-8");
    
            //获取所有Cookie
            Cookie[] cookies = request.getCookies();
    
            //遍历数组,获取所有的Cookie
            for (Cookie cookie : cookies) {
                System.out.println(cookie.getName() + "-" + cookie.getValue());
            }
    
            System.out.println("----------------------------------------");
    
            //遍历数组，获取指定的Cookie
            for (Cookie cookie : cookies) {
                if (cookie.getName().equals("姓名")) {
                    System.out.println(cookie.getName() + "-" + cookie.getValue());
                }
            }
    
        }
    
        @Override
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            doGet(request, response);
        }
    }

#### 6.3 获取中文Cookie请求效果 ####

![ac04b7a4806c4acf83d9800b6d565a3d.png][]

![d0ad6abb8c8b4db6b281c9e261b5838a.png][]

#### 6.4 解决创建和获取中文Cookie ####

6.4.1 创建中文Cookie

package com.cxyzxc.www.servlet01;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.Cookie;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import java.net.URLEncoder;
    
    @WebServlet(name = "CookieServlet04", value = "/CookieServlet04")
    public class CookieServlet04 extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //设置请求参数的编码格式，这种方式对get请求方式无效
            request.setCharacterEncoding("UTF-8");
            //设置响应编码格式为UTF-8
            response.setContentType("text/html;charset=UTF-8");
    
            //Cookie默认不支持中文，只能包含ASCII字符，所以Cookie需要对Unicode字符进行编码，否则会出现乱码
            Cookie cookie = new Cookie(URLEncoder.encode("姓名","UTF-8"),URLEncoder.encode("张三","UTF-8"));
    
            //设置Cookie的访问路径
            cookie.setPath("/webProject09_war_exploded/GetCookieValueServlet04");
    
            //发送Cookie到客户端
            response.addCookie(cookie);
        }
    
        @Override
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            doGet(request, response);
        }
    }

6.4.2 获取中文Cookie

package com.cxyzxc.www.servlet01;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.Cookie;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    import java.io.IOException;
    import java.net.URLDecoder;
    
    @WebServlet(name = "GetCookieValueServlet04", value = "/GetCookieValueServlet04")
    public class GetCookieValueServlet04 extends HttpServlet {
        @Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            //设置请求参数的编码格式，这种方式对get请求方式无效
            request.setCharacterEncoding("UTF-8");
            //设置响应编码格式为UTF-8
            response.setContentType("text/html;charset=UTF-8");
    
            //获取所有Cookie
            Cookie[] cookies = request.getCookies();
    
            //遍历数组，获取指定的Cookie
            for (Cookie cookie : cookies) {
                if (URLDecoder.decode(cookie.getName(),"UTF-8").equals("姓名")) {
                    System.out.println(URLDecoder.decode(cookie.getName(),"UTF-8") + "-" + URLDecoder.decode(cookie.getValue(),"UTF-8"));
                }
            }
    
        }
    
        @Override
        protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            doGet(request, response);
        }
    }

6.4.3 获取中文Cookie请求效果

![3493880eb78c4966814037731b1cedbb.png][]

![91c03be4f8e649309b769897c3eba0c6.png][]

### 7 Cookie优点和缺点 ###

#### 7.1 Cookie优点 ####

*  可配置到期规则
 *  简单性：Cookie是一种基于文本的轻量结构，包含简单的键值对
 *  数据持久性：Cookie默认在过期之前是可以一直存在客户端浏览器上的

#### 7.2 Cookie缺点 ####

*  大小受到限制：大多数浏览器对Cookie的大小有4K、8K字节的限制
 *  用户配置为禁用：有些用户禁用了浏览器或客户端设备接收Cookie的能力，因此限制了这一功能
 *  潜在的安全风险：Cookie可能会被篡改。会对安全性造成潜在风险或者导致依赖于Cookie的应用程序失败

[5ce31b7c0a8249308552075245f968c6.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/172881508d9a4c46853fdbccd03c1989.png
[1d43c3579bff45bf8370f743ea99a487.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/4d46e3409c5a441894d1adbd426c02af.png
[c9faaf8e73c144a09eb36cf039413632.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/2fe561d1c2174fa090a5d8c95c1d8e5e.png
[ac04b7a4806c4acf83d9800b6d565a3d.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/57bd5932e34d4ad08e2d633f070c82f2.png
[d0ad6abb8c8b4db6b281c9e261b5838a.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/9da18740b40746d7aa99dfe1dcff2082.png
[3493880eb78c4966814037731b1cedbb.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/53df263a8a0742b182e7330b8e2b5e8e.png
[91c03be4f8e649309b769897c3eba0c6.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/27/ae9650d0ddbe4f828fe593ab2d0d5cbd.png