java的会话技术和session

1、会话技术
（1）从打开一个浏览器访问某个站点，到关闭这个浏览器的整个过程，成为一次会话。
注：浏览器没关，只关闭一个网页不算会话结束；
（2）分类：cookie和session
2、cookie：客户端本地；客户端可以清除cookie；安全性不好；减轻服务器存储压力；

（1）服务器向客户端发送一个cookie：响应头set-cookie
   1）创建cookie；Cookie cookie = new Cookie（String Name，String Value）；
       键值对；set-cookie响应头；别写中文；
   2）设置持久化时间：cookie.setMaxAge(60*10)里面的单位是秒；
     不设置存储在浏览器内存中，关闭后销毁，设置后持久化到浏览器的磁盘文件；超过时间自动销毁；
3）设置携带路径：cookie.setPath(String path)；
     注：("/")任何路径都可以；("/web05")web05下的所有路径都可以；
    不设置cookie信息会在访问产生该cookie的web资源所在的路径都携带cookie信息；
    举例：cookie信息在web05的sendcookie里，那么访问完sendcookie后，访问web05下的其他项目也会有此cookie信息；
4）发送cookie：response.addCookie(Cookie cookie);

package com.oracle.cookie;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class cookieServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        //1、创建cookie对象
        Cookie cookie = new  Cookie("goods","xsphone");
        //设置cookie持久化时间----------在硬盘上保存的时间
        cookie.setMaxAge(60);
        //为cookie设置携带路径
        //cookie.setPath("/Day20/cookieServlet");
        //cookie.setPath("/Day20");
        //2、存储数据发送到客户端
        response.addCookie(cookie);
        response.getWriter().write("hello world!");
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

效果如下：

5）删除cookie：使用同名同路径的持久化时间为0的cookie进行覆盖；必须是同名同路径；

package com.oracle.cookie;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class removecookieServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        //创建一个cookie
        Cookie cookie = new  Cookie("goods","xsphone");
        cookie.setPath("/Day20");
        cookie.setMaxAge(0);
        response.addCookie(cookie);
        response.getWriter().write("hello world!");
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

重新设置时间操作显示如下：

（2）服务器接收客户端cookie：请求头cookie
1）获取所有的cookie：Cookie[] cookies = request.getCookies();
2）遍历Cookie数组：
for(Cookie cookie : cookies){
if(cookie.getName().equal(cookieName)){String cookieValue = cookie.getValue();}}

注意先访问cookieServlet！

package com.oracle.cookie;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class getcookieServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        //先获取装有cookie对象的数组
        Cookie[]  cookie = request.getCookies();
        for(Cookie  c:cookie){
            if(c.getName().equals("goods")){
                System.out.println(c.getValue());
            }
        }
        response.getWriter().write("hello world!");
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

效果如下：

控制台打印输出：

3、session：服务器；安全性好；加重服务器存储压力；

（1）获得Session对象：HttpSession session = request.getSession();
！！！在一个浏览器中sessionid是同一个；根据sessionid判断是否存在；
（2）设置session持久化时间：Cookie cookie = new Cookie("JSESSIONID",request.getSession().getId());cookie.setMaxAge(60*10)；
本质是设置cookie；
（3）session也是一个域对象；三个方法；

package com.oracle.seesion;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class session extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        HttpSession  session = request.getSession();
        String   id = session.getId();
        session.setAttribute("goods", "shouji");
        //设置JSESSIONID的持久化时间
        Cookie  cookie = new  Cookie("JSESSIONID",id);
        cookie.setPath("/Day20");
        cookie.setMaxAge(60*2);
        response.addCookie(cookie);
        response.getWriter().write(id);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

效果如下：

在不关闭浏览器的情况下，访问第二个servlet：

package com.oracle.seesion;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class seesion extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");
        HttpSession  session = request.getSession();
        String   id = session.getId();
        HttpSession  session1 = request.getSession();
        String   id1 = session1.getId();
        String name = (String)session.getAttribute("goods");
        response.getWriter().write(id+".."+id1);
        response.getWriter().write(name);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request, response);
    }
}

效果如下：

！！！可以看出ID都是一样的；
（4）session生命周期：第一次执行request.getSession()时创建；服务器（非正常）关闭时或者session过期/失效（默认30分钟）销毁；
（5）设置session销毁时间：从不操作服务器端的资源开始计时默认30分钟；session.invalidate();web.xml配置；