会话技术--cookie

Posted lxy522

tags:

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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

技术图片

技术图片

/**
* @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);
  }
}

技术图片

技术图片

@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);

 

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