客户端会话技术--cookie

会话技术

1、会话：一次会话中包含多次请求和响应。

一次会话：浏览器第一次给服务器发送资源，会话建立，直到有一方断开为止。

2、功能：在一次会话的范围内的多次请求间，共享数据。

3、方式:客户端会话技术：cookie； 服务器端会话技术：session。

cookie：

1、概念：客户端会话技术，将数据保存到客户端。

2、快速入门：

使用步骤：

1、创建cookie对象，绑定数据

new Cookie("user", "root");

2、发送cookie对象

response.addCookie(cookie1);

3、获取cookie，拿到数据

Cookie[] cookies = request.getCookies();

3、实现原理

基于响应头set-cookie和请求头cookie实现

/**
 * @program: day16_cookie&&session
 * @description:默认情况下，浏览器关闭后，cookie数据被销毁
 * @author: lixy
 * @create: 2020-05-23 19:18
 **/
@WebServlet(name = "CookieDemo1", urlPatterns = {"/cookieDemo1"})
public class CookieDemo1 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Cookie cookie1 = new Cookie("user", "李逸");
        Cookie cookie2 = new Cookie("password", "root");
        //设置cookie1的存活时间
        cookie1.setMaxAge(30);//将cookie持久化到硬盘，30秒后会自动删除这个cookie
        //设置cookie的获取范围。默认情况下，设置当前的虚拟目录
        cookie1.setPath("/");
        //设置默认方式
        cookie2.setMaxAge(-1);
        response.addCookie(cookie1);
        response.addCookie(cookie2);
​
    }
​
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}

@WebServlet(name = "CookieDemo2", urlPatterns = {"/ookieDemo2"})
public class CookieDemo2 extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");
        String contextPath = request.getContextPath();
​
        Cookie[] cookies = request.getCookies();
        for (Cookie cookie : cookies) {
            String name = cookie.getName();
            String value = cookie.getValue();
            System.out.println(name+":"+value);
        }
    }
​
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}

@WebServlet(name = "CookieTest", urlPatterns = {"/cookieTest"})
public class CookieTest extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setCharacterEncoding("utf-8");
        response.setContentType("text/html;charset=utf-8");
        String contextPath = request.getContextPath();
        String user = request.getParameter("name");
        String password = request.getParameter("password");
        Cookie[] cookies = request.getCookies();
        boolean flag = false;
        if (cookies != null && cookies.length>0){
            for (Cookie cookie : cookies) {
                String name = cookie.getName();
                if ("lastTime".equals(name)){
                    String time = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date());
                    String value = cookie.getValue();
                    //url解码
                    value = URLDecoder.decode(value, "UTF-8");
                    System.out.println("编码前："+time);
                    //url编码
                    time = URLEncoder.encode(time, "utf-8");
                    System.out.println("编码后："+time);
                    cookie.setValue(time);
                    cookie.setMaxAge(60 * 60 * 24 * 30);
                    response.addCookie(cookie);
                    flag=true;
                    response.getWriter().write("<h1>欢迎回来，您上次访问时间为"+value+"</h1>");
                    break;
                }
            }
        }
        if (cookies == null || cookies.length==0 || !flag){
            String time = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date());
            System.out.println("编码前："+time);
            //url编码
            time = URLEncoder.encode(time, "utf-8");
            System.out.println("编码后："+time);
            Cookie lastTime = new Cookie("lastTime", time);
            lastTime.setMaxAge(60 * 60 * 24 * 30);
            response.addCookie(lastTime);
            response.getWriter().write("<h1>欢迎您首次访问</h1>");
        }
    }
​
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}

//url解码 value = URLDecoder.decode(value, "UTF-8");

System.out.println("编码前："+time);

//url编码 time = URLEncoder.encode(time, "utf-8");

System.out.println("编码后："+time);