// 上面提到過(guò)用戶(hù)的請(qǐng)求會(huì)攜帶cookie  所以要從客戶(hù)端獲取到cookie
Cookie[] cookies = req.getCookies();// --返回Cookie數(shù)組
// 創(chuàng)建cookie  兩個(gè)參數(shù)  鍵name   --   值value
Cookie cookie = new Cookie("LoginTimes",System.currentTimeMillis()+"");
// 獲取鍵
cookie.getName()
// 獲取值
cookie.getValue()
// 設(shè)置Cookie有效期  --> 24*60*60表示24小時(shí)*60分鐘*60秒
cookie.setMaxAge(24*60*60);
// 響應(yīng)給客戶(hù)端一個(gè)Cookie(信件)
resp.addCookie(cookie);

// 參考下方的doGet方法體
{
        // -- 顯示上次訪問(wèn)的時(shí)間
        req.setCharacterEncoding("UTF-8");
        resp.setCharacterEncoding("UTF-8");
 resp.setHeader("contenttype","text/html;charset=UTF-8");
System.out.println("resp編碼："+resp.getCharacterEncoding());
        System.out.println("req編碼："+req.getCharacterEncoding());
        PrintWriter out = resp.getWriter();
        // 從客戶(hù)端獲取Cookie
        Cookie[] cookies = req.getCookies();// --返回Cookie數(shù)組
        // 判斷該用戶(hù)是否已經(jīng)存在Cookie
        if (cookies!=null){
            out.write("LastTime Login Time:");
            for (Cookie cookie : cookies) {
                // 遍歷找到訪問(wèn)時(shí)間的Cookie  getName獲得cookie中的鍵
                if (cookie.getName().equals("LoginTimes")){
                    // 獲取LoginTimes-Cookie的值  -- value
                    long l = Long.parseLong(cookie.getValue());
                    Date date = new Date(l);
                    out.write(date.toLocaleString());
                }
            }
        }
        // 記錄本次訪問(wèn)的時(shí)間  --> 新建Cookie
        Cookie cookie = new Cookie("LoginTimes",System.currentTimeMillis()+"");
// 設(shè)置Cookie有效期  --> 24*60*60表示24小時(shí)*60分鐘*60秒
        cookie.setMaxAge(24*60*60);
        // 響應(yīng)給客戶(hù)端一個(gè)Cookie(信件)
        resp.addCookie(cookie);
    }

// setCharacterEncoding意思是在程序中將請(qǐng)求和響應(yīng)均置為utf-8編碼 但是可能瀏覽器會(huì)無(wú)法解析
        req.setCharacterEncoding("UTF-8");
        resp.setCharacterEncoding("UTF-8");
// 瀏覽器使用的編碼集可能與UTF-8不同  所以此處設(shè)置瀏覽器采用UTF-8編碼
        resp.setHeader("content-type","text/html;charset=UTF-8");

// 編碼
URLEncoder.encode("張三","utf-8");
// 解碼
URLDecoder.decode("李四","utf-8");

/*源碼解析：以秒為單位指定cookie的最大期限；如果否定，則表示未存儲(chǔ)cookie；如果為零，則刪除cookie
*/
resp.setMaxAge(0);

// Session對(duì)象
HttpSession session = req.getSession();
// session創(chuàng)建時(shí)間
out.write("創(chuàng)建時(shí)間："+session.getCreationTime()+"\n");
// sessionID獲取
out.write("SessionID:"+session.getId()+"\n");
// session上次訪問(wèn)時(shí)間
out.write("上次訪問(wèn)時(shí)間："+session.getLastAccessedTime()+"\n");
// setAttribute設(shè)置鍵值屬性  getAttribute根據(jù)鍵獲取值
// getValue 根據(jù)鍵獲取值-->從2.2開(kāi)始唄getA他tribute替代
// removeAttribute(String name) 刪除name鍵綁定的對(duì)象 如果不存在則不執(zhí)行任何操作
// isNew() 判斷該Session是否為新創(chuàng)建的
//注銷(xiāo)Session  
session.invalidate();
//注銷(xiāo)Session也會(huì)注銷(xiāo)掉SessionID

// Servlet 1
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 編碼問(wèn)題
        req.setCharacterEncoding("UTF-8");
        resp.setCharacterEncoding("UTF-8");
        resp.setHeader("content-type","text/html;charset:utf-8");
        // 流
        PrintWriter out = resp.getWriter();
        // Session
        // -- 1.獲取Session對(duì)象
        HttpSession session = req.getSession();
        // -- 2.獲取SessionID
        String id = session.getId();
        // -- 3.判斷該ID是否存在
        if (session.isNew()) {
            out.write("SessionID已存在："+id);
        }else {
            out.write("Session創(chuàng)建成功，ID："+id);
        }
        out.write("<h1>數(shù)據(jù)已寫(xiě)出，跳轉(zhuǎn)checkData查看</h1>");
        // -- 4.寫(xiě)出數(shù)據(jù)
        session.setAttribute("name","張三");
    }
// Servlet  2
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 編碼
        req.setCharacterEncoding("UTF-8");
        resp.setCharacterEncoding("UTF-8");
        resp.setHeader("content-type","text/html;charset=UTF-8");
        // 獲取數(shù)據(jù)
        HttpSession session = req.getSession();
        String name = (String) session.getAttribute("name");
        // 寫(xiě)出數(shù)據(jù)
        resp.getWriter().write("name:"+name);
    }