簡(jiǎn)單聊聊Java Servlet中的Cookie和Session機(jī)制

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 java.io.IOException;
import java.io.PrintWriter;

public class SetCookieServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.創(chuàng)建Cookie對(duì)象
        //首先需要一個(gè)cookie對(duì)象,這里我們需要兩個(gè)cookie對(duì)象，一個(gè)來(lái)存儲(chǔ)用戶(hù)名（username——java），一個(gè)來(lái)存儲(chǔ)密碼（pwd——javas）
        Cookie username = new Cookie("uesrname","java");
        Cookie pwd = new Cookie("pwd","javas");
        //當(dāng)我們創(chuàng)建好兩個(gè)cookie對(duì)象之后，就可以對(duì)這兩個(gè)對(duì)象進(jìn)行一系列操作
        //比如：設(shè)置他的過(guò)期時(shí)間，這里我們將username的過(guò)期時(shí)間設(shè)置為永久
        username.setMaxAge(-1);
        //密碼pwd的過(guò)期時(shí)間設(shè)置為一分鐘,注意他的過(guò)期時(shí)間是以秒為單位
        pwd.setMaxAge(60);
        //2.將 Cookie 對(duì)象關(guān)聯(lián)到response上
        resp.addCookie(username);
        resp.addCookie(pwd);

        //顯示給用戶(hù)部分的信息
        resp.setCharacterEncoding("utf-8");
        resp.setContentType("text/html");
        //然后寫(xiě)入響應(yīng)給客戶(hù)端的內(nèi)容
        PrintWriter writer = resp.getWriter();
        writer.println("<h1>Cookie 設(shè)置成功</h1>");

    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

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 java.io.IOException;
import java.io.PrintWriter;

public class GetCookieServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //讀取Cookie的信息
        //因?yàn)榭蛻?hù)端的cookie可能會(huì)有多個(gè)，所以我們使用數(shù)組來(lái)接收,注意：cookie是從request獲取的
        Cookie[] cookies = req.getCookies();
        resp.setContentType("text/html");
        resp.setCharacterEncoding("utf-8");
        PrintWriter writer = resp.getWriter();
        //然后讀取cookie的內(nèi)容
        for (Cookie item: cookies
             ) {
            writer.println(String.format("<h1>Cookie key: %s,Cookie value: %s</h1>",item.getName(),item.getValue()));
        }
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}

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

public class SessionServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //關(guān)于 session 的讀寫(xiě)
        //1.先獲取到session到對(duì)象
        HttpSession session = req.getSession();

        //2.得到session的屬性
        //2.1獲取到session的ID
        String sessionID = session.getId();


        //返回響應(yīng)信息
        resp.setContentType("text/html");
        resp.setCharacterEncoding("utf-8");
        PrintWriter writer = resp.getWriter();
        writer.println("<h1>歡迎訪(fǎng)問(wèn)頁(yè)面</h1>");
        //輸出sessionID
        writer.println(String.format("<h3>SessionID : %s </h3>",sessionID));
        //輸出session的創(chuàng)建時(shí)間，因?yàn)閟ession的創(chuàng)建時(shí)間是一個(gè)時(shí)間戳，所以我們需要將其強(qiáng)轉(zhuǎn)成我們能看得懂的時(shí)間
        writer.println(String.format("<h3>Session創(chuàng)建時(shí)間: %s</h3>",new Date(session.getCreationTime())));
        //輸出session的最后訪(fǎng)問(wèn)時(shí)間
        writer.println(String.format("<h3>Session的最后訪(fǎng)問(wèn)時(shí)間: %S</h3>",new Date(session.getLastAccessedTime())));
        
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req, resp);
    }
}