一、會話跟蹤技術(shù)

會話：用戶打開瀏覽器，訪問web服務(wù)器的資源，會話建立，直到有一方斷開連接，會話結(jié)束。在一次會話中可以包含多次請求和響應(yīng)。

會話跟蹤：一種維護(hù)瀏覽器狀態(tài)的方法，服務(wù)器需要識別多次請求是否來自于同一瀏覽器，以便在同一次會話的多次請求間共享數(shù)據(jù)。實現(xiàn)方式有：Cookie（客戶端會話跟蹤技術(shù)）、Session（服務(wù)端會話跟蹤技術(shù)）

二、Cookie

基本使用

Cookie：客戶端會話技術(shù)，將數(shù)據(jù)保存到客戶端，以后每次請求都攜帶Cookie數(shù)據(jù)進(jìn)行訪問.

1. 發(fā)送cookie

package com.ithecheng.web;

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("/aServlet")
public class AServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //發(fā)送cookie

        //1.創(chuàng)建cookie對象
        Cookie cookie = new Cookie("username","zs");
        //2.發(fā)送cookie，response
        response.addCookie(cookie);

    }
}

2. 獲取cookie

package com.ithecheng.web;

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("/bServlet")
public class BServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //獲取cookie

        //1. 獲取cookie數(shù)組
        Cookie[] cookies = request.getCookies();

        //2. 遍歷數(shù)組
        for (Cookie cookie : cookies) {
            //3. 獲取數(shù)據(jù)
            String name = cookie.getName();
            if ("username".equals(name)){
                String value = cookie.getValue();
                System.out.println(name + ":" + value);

                break;

            }

        }


    }
}

cookie原理

cookie是通過http協(xié)議實現(xiàn)的，服務(wù)器通過響應(yīng)頭set-cookie給瀏覽器cookie數(shù)據(jù)，瀏覽器通過請求頭cookie攜帶cookie數(shù)據(jù)訪問服務(wù)器。

cookie使用細(xì)節(jié)

1. cookie存活時間：默認(rèn)情況下，cookie存儲在瀏覽器內(nèi)存中，當(dāng)瀏覽器關(guān)閉，內(nèi)存釋放，cookie被銷毀。除此之外，可以使用setMaxAge（int seconds）設(shè)置cookie存活時間

package com.ithecheng.web;

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("/aServlet")
public class AServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //發(fā)送cookie

        //1.創(chuàng)建cookie對象
        Cookie cookie = new Cookie("username","zs");


        //設(shè)置存活時間 一周
        cookie.setMaxAge(60*60*24*7); //正數(shù) 存儲的時間；負(fù)數(shù) 默認(rèn)值，存在內(nèi)存中；零 刪除對應(yīng)cookie


        //2.發(fā)送cookie，response
        response.addCookie(cookie);

    }
}

2. cookie存儲中文
   cookie不能直接存儲中文，如需要存儲，則需要進(jìn)行轉(zhuǎn)碼：URL編碼
   cookie存儲中文時轉(zhuǎn)碼：

package com.ithecheng.web;

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.URLEncoder;

@WebServlet("/aServlet")
public class AServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //發(fā)送cookie

        //1.創(chuàng)建cookie對象
//        Cookie cookie = new Cookie("username","zs");


        String value = "張三";
        value = URLEncoder.encode(value, "UTF-8");
        System.out.println("存儲數(shù)據(jù)："+ value);
        Cookie cookie = new Cookie("username",value);

        //設(shè)置存活時間 一周
        cookie.setMaxAge(60*60*24*7); //正數(shù) 存儲的時間；負(fù)數(shù) 默認(rèn)值，存在內(nèi)存中；零 刪除對應(yīng)cookie


        //2.發(fā)送cookie，response
        response.addCookie(cookie);

    }
}

解析cookie的中文：

package com.ithecheng.web;

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;
import java.net.URLEncoder;

@WebServlet("/bServlet")
public class BServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //獲取cookie

        //1. 獲取cookie數(shù)組
        Cookie[] cookies = request.getCookies();

        //2. 遍歷數(shù)組
        for (Cookie cookie : cookies) {
            //3. 獲取數(shù)據(jù)
            String name = cookie.getName();
            if ("username".equals(name)){
                String value = cookie.getValue();
                //URL解碼
                value = URLDecoder.decode(value,"UTF-8");
                System.out.println(name + ":" + value);

                break;

            }

        }


    }
}

session

基本使用

session：服務(wù)端會話跟蹤技術(shù)，將數(shù)據(jù)保存到服務(wù)端（JavaEE提供HttpSession接口，來實現(xiàn)一次會話多次請求間數(shù)據(jù)共享）

1. session中存儲數(shù)據(jù)

package com.ithecheng.web.session;

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

@WebServlet("/demo1")
public class Sessiondemo1 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 存儲數(shù)據(jù)到session中
        // 1. 獲取session對象
        HttpSession session = request.getSession();

        // 2. 存儲數(shù)據(jù)
        session.setAttribute("username","zs");
    }
}

2. session中獲取數(shù)據(jù)

package com.ithecheng.web.session;

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

@WebServlet("/demo2")
public class Sessiondemo2 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 從session中獲取數(shù)據(jù)

        // 1. 獲取session對象
        HttpSession session = request.getSession();
        // 2. 獲取數(shù)據(jù)
        Object username = session.getAttribute("username");
        System.out.println(username);

    }
}

session原理

session實現(xiàn)是基于cookie的