Java——cookie细节

Myth丶恋晨 2022-01-30 11:59 148阅读 0赞

**在创建cookie时，需要了解几点关于cookie的小知识，今天就介绍四点关于cookie的细节**  
**我们先创建一个Servlet类型的CookieDemo2，用来统一接收cookie**

package cookie;
    
    import java.io.IOException;
    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;
    
    @WebServlet("/CookieDemo2")
    public class CookieDemo2 extends HttpServlet {
    
    	private static final long serialVersionUID = 1L;
    	
    	/*
    	实现原理:
    		* 基于响应头set-cookie和请求头cookie实现 
    	*/
    	
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		//3、获取cookie
    		Cookie[] cookies=request.getCookies();
    		//获取数据遍历cookie
    		if(cookies!=null) {
    			for(Cookie coookie:cookies) {
    				String name=coookie.getName();
    				String value=coookie.getValue();
    				System.out.println(name+":"+value);
    			}
    		}
    	}
    	
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    
    }

1、一次可不可以发送多个cookie?

1.  可以
2.  可以创建多个Cookie对象，使用response调用多次addCookie方法发送cookie即可。

创建servlet类型CookieDemo11,运行tomcat，  
网址先输入 [http://localhost:8888/studyWeb/CookieDemo11][http_localhost_8888_studyWeb_CookieDemo11]  
在输入 [http://localhost:8888/studyWeb/CookieDemo2][http_localhost_8888_studyWeb_CookieDemo2]  
即可在开发者模式或服务器看到创建了多个cookie

package cookie;
    
    import java.io.IOException;
    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;
    
    @WebServlet("/CookieDemo11")
    public class CookieDemo11 extends HttpServlet {
    	
    	private static final long serialVersionUID = 1L;
    	
    	/*
    	 一次可不可以发送多个cookie?
    		* 可以
    		* 可以创建多个Cookie对象，使用response调用多次addCookie方法发送cookie即可。 
    	*/
    	
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		//1、创建cookie对象
    		Cookie c1=new Cookie("msg","hello");
    		Cookie c2=new Cookie("url","www.baidu.com");
    		//2、发送cookie
    		response.addCookie(c1);
    		response.addCookie(c2);
    	}
    	
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg_size_16_color_FFFFFF_t_70]

*  2、cookie在浏览器中保存多长时间？
    
    1.  默认情况下，当浏览器关闭后，Cookie数据被销毁
    2.  持久化存储：  
        setMaxAge(int seconds)
        
        1.  正数：将Cookie数据写到硬盘的文件中。持久化存储。并指定cookie存活时间，时间到后，cookie文件自动失效
        2.  负数：默认值
        3.  零：删除cookie信息

创建servlet类型CookieDemo12,运行tomcat，  
网址先输入 [http://localhost:8888/studyWeb/CookieDemo12][http_localhost_8888_studyWeb_CookieDemo12]  
在输入 [http://localhost:8888/studyWeb/CookieDemo2][http_localhost_8888_studyWeb_CookieDemo2]  
自己多次尝试即可掌握

package cookie;
    
    import java.io.IOException;
    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;
    
    @WebServlet("/CookieDemo12")
    public class CookieDemo12 extends HttpServlet {
    	
    	private static final long serialVersionUID = 1L;
    	
    	/*
    	cookie在浏览器中保存多长时间？
    		1. 默认情况下，当浏览器关闭后，Cookie数据被销毁
    		2. 持久化存储：
    			* setMaxAge(int seconds)
    				1. 正数：将Cookie数据写到硬盘的文件中。持久化存储。并指定cookie存活时间，时间到后，cookie文件自动失效
    				2. 负数：默认值
    				3. 零：删除cookie信息
    	*/
    	
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		//1、创建cookie对象
    		Cookie c=new Cookie("msg","hello");
    		//设置cookie的存活时间
    		//c.setMaxAge(60); 	//将cookie持久化到磁盘，60秒后自动删除cookie文件
    		//c.setMaxAge(0); 	//删除cookie信息
    		c.setMaxAge(-1);	//默认情况
    		//2、发送cookie
    		response.addCookie(c);
    	}
    	
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    
    }

1.  cookie能不能存中文？  
    1、 在tomcat 8 之前 cookie中不能直接存储中文数据
    
     *  需要将中文数据转码—一般采用URL编码，利用自带的URL编码
    
    2、 在tomcat 8 之后，cookie支持中文数据。特殊字符还是不支持，建议使用URL编码存储，URL解码解析
    
     *  但是在火狐浏览器F12开发者模式，cookie中文是乱码，而谷歌浏览器显示的出中文

创建servlet类型CookieDemo13,运行tomcat，  
网址先输入 [http://localhost:8888/studyWeb/CookieDemo13][http_localhost_8888_studyWeb_CookieDemo13]  
在输入 [http://localhost:8888/studyWeb/CookieDemo2][http_localhost_8888_studyWeb_CookieDemo2]

package cookie;
    
    import java.io.IOException;
    //import java.net.URLDecoder;
    //import java.net.URLEncoder;
    
    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;
    
    @WebServlet("/CookieDemo13")
    public class CookieDemo13 extends HttpServlet {
    	
    	private static final long serialVersionUID = 1L;
    	
    	/*
    	cookie能不能存中文？
    		* 在tomcat 8 之前 cookie中不能直接存储中文数据。
    			* 需要将中文数据转码，一般使用URL编码和解码
    		* 在tomcat 8 之后，cookie支持中文数据。特殊字符还是不支持，建议使用URL编码存储，URL解码解析
    	但是在火狐浏览器F12开发者模式，cookie中文是乱码，而谷歌浏览器显示的出中文
    	*/
    	
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		//1、创建cookie对象
    		Cookie c=new Cookie("msg","你好");
    //		String value=c.getValue();
    //		System.out.println("编码前："+value);
    //		value=URLEncoder.encode(value, "utf-8");
    //		System.out.println("编码后："+value);
    //		value=URLDecoder.decode(value, "utf-8");
    //		System.out.println("解码后："+value);
    		//2、发送cookie
    		response.addCookie(c);
    	}
    	
    	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    		doGet(request, response);
    	}
    
    }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg_size_16_color_FFFFFF_t_70 1]  
4.、cookie共享问题？  
1. 假设在一个tomcat服务器中，部署了多个web项目，那么在这些web项目中cookie能不能共享？

*  1.1、默认情况下cookie不能共享
 *  1.2、setPath(String path):设置cookie的获取范围。默认情况下，设置当前的虚拟目录
 *  1.3、如果要共享，则可以将path设置为"/"

1.  不同的tomcat服务器间cookie共享问题？

*  2.1、.setDomain(String path):如果设置一级域名相同，那么多个服务器之间cookie可以共享
 *  2.2、setDomain(".baidu.com"),那么tieba.baidu.com和news.baidu.com中cookie可以共享

创建servlet类型CookieDemo14,运行tomcat，两个CookieDemo2一样，不在同一个项目  
网址先输入 [http://localhost:8888/studyWeb/CookieDemo14][http_localhost_8888_studyWeb_CookieDemo14]  
在输入 [http://localhost:8888/studyWeb/CookieDemo2][http_localhost_8888_studyWeb_CookieDemo2]  
在输入 [http://localhost:8888/studyWeb2/CookieDemo2][http_localhost_8888_studyWeb2_CookieDemo2]

可以发现运行CookieDemo14后，两个项目都能获取到这个cookie。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg_size_16_color_FFFFFF_t_70 2]![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg_size_16_color_FFFFFF_t_70 3]

[http_localhost_8888_studyWeb_CookieDemo11]: http://localhost:8888/studyWeb/CookieDemo11
[http_localhost_8888_studyWeb_CookieDemo2]: http://localhost:8888/studyWeb/CookieDemo2
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg_size_16_color_FFFFFF_t_70]: /images/20220130/53a40680f1ea473c9c8410430cfab161.png
[http_localhost_8888_studyWeb_CookieDemo12]: http://localhost:8888/studyWeb/CookieDemo12
[http_localhost_8888_studyWeb_CookieDemo13]: http://localhost:8888/studyWeb/CookieDemo13
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg_size_16_color_FFFFFF_t_70 1]: /images/20220130/7e8aad30c904491b8f7e84bf6e91a270.png
[http_localhost_8888_studyWeb_CookieDemo14]: http://localhost:8888/studyWeb/CookieDemo14
[http_localhost_8888_studyWeb2_CookieDemo2]: http://localhost:8888/studyWeb2/CookieDemo2
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg_size_16_color_FFFFFF_t_70 2]: https://img-blog.csdnimg.cn/20190519152315668.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg==,size_16,color_FFFFFF,t_70
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl80MjEwOTAxMg_size_16_color_FFFFFF_t_70 3]: /images/20220130/8fb7ac20b19d4388b5e74b8a5ae2850a.png