Cookie

Cookie是servlet发送到Web浏览器的少量信息，该信息由浏览器保存，然后发送回服务器。一般情况下，Cookie是以键值对进行表示的(key-value)，Cookie的值可以唯一地标识客户端，因此Cookie常用于会话管理。servlet通过使用HttpServletResponse#addCookie方法将cookie发送到浏览器，该方法将字段添加到http响应头，以便一次一次地将cookie发送到浏览器，每个Cookie的大小限定为4kb。

创建Cookie

客户端没有Cookie        ->        服务器创建Cookie        ->        通知客户端保存Cookie        ->        通过响应头Set-Cookie通知客户端保存Cookie（Set-Cookie：key=value）        ->客户端收到响应后发现set-cookie响应头，查看有没有Cookie，如果没有就创建如果有就修改。

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 {}@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {doPost(request,response);}@Overrideprotected 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 {//创建CookieCookie cookie = new Cookie("key","value");//通知客户端保存response.addCookie(cookie);response.getWriter().write("Cookie创建成功");}
}

Cookie的创建
Cookie的获取
Cookie值的修改
Cookie的存活周期
Cookie的默认存活时间（会话）
Cookie立即删除
Cookie存活5秒
Cookie的路径设置
Cookie的用户登录练习

服务器获取Cookie

客户端有了Cookie的值        ->        通过请求头：Cookie：key=value 把Cookie信息发送给服务器        ->        服务器获取客户端发送过来的Cookie只需要一行代码{request.getCookies()：返回Cookie[]数组}

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()获取Cookie的Key值，getValue()方法获取Cookie的value值response.getWriter().write("Cookie{" + cookie.getName() + ":" + cookie.getValue() + "} 
");}Cookie iWantCookie = CookieUtil.findCookie("key",cookies);//如果不等于null意味着找到了Cookieif (iWantCookie != null){response.getWriter().write("找到了Cookie");}}...
}

package com.pero.servlet.util;import jakarta.servlet.http.Cookie;public class CookieUtil {/*** 查找指定名称的Cookie对象* @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：//创建需要修改的同名Cookie对象//在构造器中同时赋予新的Cookie值
//        Cookie cookie = new Cookie("key","newValue");//调用response.addCookie(Cookie)
//        response.addCookie(cookie);
//        response.getWriter().write("key的Cookie的值已经修改");//方法二//查找需要修改的Cookie对象Cookie cookie = CookieUtil.findCookie("key",request.getCookies());//调用setValue()方法付于心的Cookie值if (cookie != null){cookie.setValue("NewCookie");}//调用response.addCookie(cookie)通知客户端保存修改response.addCookie(cookie);}...
}

Cookie的生命控制

Cookie的生命控制指的是如何管理Cookie什么时候被销毁（删除）。setMaxAge()；整数表示在指定秒数后过期，负数表示浏览器一关Cookie就会被删除(程序默认)，0表示立刻删除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);    //设置Cookie5秒后删除response.addCookie(cookie);response.getWriter().write("创建了5秒钟的Cookie");}protected void deleteNowCookie(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {//查找需要删除的CookieCookie cookie = CookieUtil.findCookie("key",request.getCookies());if (cookie != null){//设置cookie.setMaxAge(0);立刻销毁Cookiecookie.setMaxAge(0);//response.addCookie();浏览器保存response.addCookie(cookie);response.getWriter().write("key的Cookie已经被删除");}}protected void defaultLifeCookie(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {Cookie cookie = new Cookie("defaultLife","defaultLife");cookie.setMaxAge(-1);   //设置存活时间为浏览器退出后Cookie被销毁response.addCookie(cookie);}...
}

Cookie有效路径Path的设置

Cookie的path属性可以有效的过滤那些Cookie可以发送给服务器那些不发送，path属性是通过请求的地址来进行过滤。

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()得到工程路径cookie.setPath(request.getContextPath() + "/file");response.addCookie(cookie);response.getWriter().write("创建了一个带有Path路径的Cookie");}...
}

Cookie练习免用户名登陆

第一次登录时：客户端（浏览器）第一次访问，服务器返回给客户端登陆页面，填写用户名和密码后提交给服务器，服务器获取用户名和密码，判断用户名和密码是否正确，正确允许登录，错误不允许登录，把用户名保存为Cookie发送给客户端，浏览器有了用户名和Cookie信息；

第二次登陆时：客户端（浏览器）第二次访问服务器会把Cookie信息发给服务器，服务器返回给客户端带用户名的登录界面。

package com.pero.servlet.cookie_session;import jakarta.servlet.*;
import jakarta.servlet.http.*;import java.io.IOException;public class LoginServlet extends HttpServlet {@Overridepublic 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)){//登陆成功Cookie cookie = new Cookie("username", username);cookie.setMaxAge(60*60*24*7);   //cookie一周内有效response.addCookie(cookie);System.out.println("登陆成功");}else {System.out.println("登陆失败");}}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {}
}

<%--Created by IntelliJ IDEA.User: AdministratorDate: 2023/3/16Time: 18:35To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>



用户名：
密  码：

Session

Session是一个接口（HttpSession），Session是会话，用来维护一个客户端和服务器之间关联的一种技术，每个客户端都有自己的一个Session会话，Session会话中经常用来保存用户登录之后的信息。

创建Session和获取

request.getSession()：第一次调用是创建Session会话，之后都是调用，获取前面创建好的Session会话对象；

isNew()：判断是不是新创建出来的Session，true表示新创建，false表示获取之前创建的；

getId()：得到Session会话的id值，每一个会话都有一个id值，这个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 {//创建和获取Session会话对象HttpSession session = request.getSession();//判断当前Session会话是否是新创建出来的boolean isNew = session.isNew();//获取Session会话的唯一标识String id = session.getId();response.getWriter().write("得到的Session的ID：" + id + " 
");response.getWriter().write("Session是否为新创建的：" + isNew + " 
");}}

Session的创建和获取
Session域数据的存储
Session域数据的获取
Session的存活周期
Session默认超时配置
Session5秒超时销毁
Session立刻销毁
浏览器和Session绑定的原理

Session域中数据的存取

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("从Session中获取key的值为：" + attribute);}protected void setAttributeSession(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {HttpSession session = request.getSession();session.setAttribute("key","value");response.getWriter().write("已经向Session中存储值");}...
}

Session生命周期

Session超时是指客户端两次请求的最大间隔时间。

public void setMaxInactiveInterval(int interval)：设置Session超时时间（以秒为单位），超过指定时长Session会被销毁，值为正数的时候，设定Session的超市时长，值为负数的时候，Session永不超时；

public void invalidate()：让Session会话立刻超时无效；

public int getMaxInactiveInterval()：获取Session的超时时间；

Session的默认超时时长为：Session的默认超时时长为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的默认超时时长为" + maxInactiveInterval + "秒");}...
}

 如果调整web工程的超时时长，可以在web.xml中进行配置。

10

也可以通过setMaxInactiveInterval(int interval)设置Session超时时间

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();//设置当前Session5秒后超时session.setMaxInactiveInterval(5);response.getWriter().write("当前Session已经设置为5秒后超时");}...
}

设置Session立刻超时

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();//设置当前Session立刻超时session.invalidate();response.getWriter().write("当前Session立刻超时关闭");}...
}

浏览器和Session之间关联的技术

Session技术底层是基于Cookie技术实现的。