java的會話技術和session

1、會話技術
（1）從打開一個瀏覽器訪問某個站點，到關閉這個瀏覽器的整個過程，成為一次會話。
注：瀏覽器沒關，只關閉一個網頁不算會話結束；
（2）分類：cookie和session
2、cookie：客戶端本地；客戶端可以清除cookie；安全性不好；減輕服務器存儲壓力；

 

（1）服務器向客戶端發送一個cookie：響應頭set-cookie
   1）創建cookie；Cookie cookie = new Cookie（String Name，String Value）；
       鍵值對；set-cookie響應頭；別寫中文；
   2）設置持久化時間：cookie.setMaxAge(60*10)里面的單位是秒；
     不設置存儲在瀏覽器內存中，關閉后銷毀，設置后持久化到瀏覽器的磁盤文件；超過時間自動銷毀；
3）設置攜帶路徑：cookie.setPath(String path)；
     注：("/")任何路徑都可以；("/web05")web05下的所有路徑都可以；
    不設置cookie信息會在訪問產生該cookie的web資源所在的路徑都攜帶cookie信息；
    舉例：cookie信息在web05的sendcookie里，那么訪問完sendcookie后，訪問web05下的其他項目也會有此cookie信息；
4）發送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、創建cookie對象
        Cookie cookie = new  Cookie("goods","xsphone");
        //設置cookie持久化時間----------在硬盤上保存的時間
        cookie.setMaxAge(60);
        //為cookie設置攜帶路徑
        //cookie.setPath("/Day20/cookieServlet");
        //cookie.setPath("/Day20");
        //2、存儲數據發送到客戶端
        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）刪除cookie：使用同名同路徑的持久化時間為0的cookie進行覆蓋；必須是同名同路徑；

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");
        //創建一個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);
    }
}

重新設置時間操作顯示如下：

 

（2）服務器接收客戶端cookie：請求頭cookie
1）獲取所有的cookie：Cookie[] cookies = request.getCookies();
2）遍歷Cookie數組：
for(Cookie cookie : cookies){
if(cookie.getName().equal(cookieName)){String cookieValue = cookie.getValue();}}

注意先訪問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");
        //先獲取裝有cookie對象的數組
        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：

控制台打印輸出：

 

3、session：服務器；安全性好；加重服務器存儲壓力；

 

（1）獲得Session對象：HttpSession session = request.getSession();
！！！在一個瀏覽器中sessionid是同一個；根據sessionid判斷是否存在；
（2）設置session持久化時間：Cookie cookie = new Cookie("JSESSIONID",request.getSession().getId());cookie.setMaxAge(60*10)；
本質是設置cookie；
（3）session也是一個域對象；三個方法；

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");
        //設置JSESSIONID的持久化時間
        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：

 

在不關閉瀏覽器的情況下，訪問第二個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都是一樣的；
（4）session生命周期：第一次執行request.getSession()時創建；服務器（非正常）關閉時或者session過期/失效（默認30分鍾）銷毀；
（5）設置session銷毀時間：從不操作服務器端的資源開始計時默認30分鍾；session.invalidate();web.xml配置；