Cookie

在服务器中写一个Cookie键值对，然后把它扔进响应值中，于是在浏览器访问当前web项目时会得到响应值，并且把这个响应值中的Cookie数据存在浏览器中，下次，在服务器中就可以先获得刚才的Cookie数据，然后就可以以这个Cookie数据为标记，共享数据

简单的代码实现：

• 创建Cookie数据，浏览器保存，控制台输出刚才创建的Cookie数据
  即先访问co1，再访问co2
• 服务器将Cookie数据放进响应头中，再给浏览器
  浏览器将Cookie数据放入请求头中，再给服务器

• 创建Cookie数据：

package com.itjh.servlet;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("/co1")
public class Servletcook1 extends HttpServlet {@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doGet(req, resp);}@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {Cookie cookie=new Cookie("name","zhangsan");resp.addCookie(cookie);}
}

• 输出Cookie数据：

package com.itjh.servlet;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("/co2")
public class Servletcook2 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {Cookie[] cookies =req.getCookies();for (Cookie c:cookies) {if (c.getName().equals("name")){System.out.println(c.getName()+":"+c.getValue());}}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req,resp);}
}

结果：

[INFO] Running war on http://localhost:8080/filterday01
[INFO] Using existing Tomcat server configuration at C:\\Users\\李家院刘俊辉\\new start\\filterday01\\target\\tomcat
[INFO] create webapp with contextPath: /filterday01
四月 10, 2023 11:37:57 上午 org.apache.coyote.AbstractProtocol init
信息: Initializing ProtocolHandler ["http-bio-8080"]
四月 10, 2023 11:37:57 上午 org.apache.catalina.core.StandardService startInternal
信息: Starting service Tomcat
四月 10, 2023 11:37:57 上午 org.apache.catalina.core.StandardEngine startInternal
信息: Starting Servlet Engine: Apache Tomcat/7.0.47
四月 10, 2023 11:37:58 上午 org.apache.coyote.AbstractProtocol start
信息: Starting ProtocolHandler ["http-bio-8080"]name:zhangsan

存储中文时，需要进行转码：

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("/co1")
public class Servletcook1 extends HttpServlet {@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {this.doGet(req, resp);}@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {String value="王五";//将中文数据转换成utf-8格式，网页才能识别，//就是指网页能正常打开，//于是进行编码value=URLEncoder.encode(value,"UTF-8");Cookie cookie=new Cookie("name",value);resp.addCookie(cookie);}
}

package com.itjh.servlet;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("/co2")
public class Servletcook2 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {Cookie[] cookies =req.getCookies();for (Cookie c:cookies) {if (c.getName().equals("name")){String cc=c.getValue();//未进行转码，所以得到的乱码System.out.println(cc);//将得到的数据进行转码，否则得到时乱码cc=URLDecoder.decode(cc,"UTF-8");System.out.println(c.getName()+":"+cc);}}}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req,resp);}
}

想要定义时间：

定义Cookie数据的时候就可以进行Cookie数据再浏览器上存在时间的设置

@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {String value="王五";value=URLEncoder.encode(value,"UTF-8");Cookie cookie=new Cookie("name",value);//一天的时间cookie.setMaxAge(60*60*24);resp.addCookie(cookie);}

Session

• 先获得Session域，然后再进行设置或者获得
• 怎么保证每一次获得的Session对象都是同一个呢？
  因为Session是基于Cookie来实现的，TomCat在拿到Session数据之后就会将当时前的数据打包成Cookie数据，然后再放在响应头中交给浏览器，然后浏览器访问服务器时，就会将这个Cookie数据放入请求头中，服务器看Session域中有没有这个数据，没有的话就自己创建一个，综上所述，就能是同一个Session对象了

代码实现：

package com.itjh.servlet;import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;@WebServlet("/servletsession1")
public class servletsession1 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//获得Session对象HttpSession httpSession=request.getSession();//设置键值对httpSession.setAttribute("age","28");System.out.println("doget。。1。。。");}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doGet(request, response);}
}

package com.itjh.servlet;import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.io.IOException;@WebServlet("/servletsession2")
public class servletsession2 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//获得Session对象HttpSession httpSession=request.getSession();//通过键值对得到Session域中的内容Object age=httpSession.getAttribute("age");System.out.println(age);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {this.doGet(request, response);}
}

对比：