cookie - a time to access the page on tips

      Case: Remember the last access time
        1. Requirements:
            1. Access a Servlet, if it is the first visit, the prompt: Hello, welcome to your first visit.
            2. If it is not the first visit, the prompt: Welcome back, your last visit time: displays the time string

        2. Analysis:
            1. Cookie can be accomplished using
            2. Servlet in the server to determine whether there is a file called lastTime of the cookie
                1 are: not the first visit to
                    1. response data: Welcome back, your last visit time: June 10, 2018 11:50:20
                    2. write back Cookie: lastTime = 2018 Nian 6 Yue 10 11:50:01
                2. no: is the first visit to
                    1. The response data: Hello, welcome to your first visit
                    2. write back Cookie: lastTime = 2018 Nian 6 Yue 10, 11:50:00

 

important point:

Must be set before the encoding stream 1. Get PrintWriter

 response.setContentType("text/html;charset=utf-8");

2. cookie can not contain special characters, such as spaces, so to encode and decode

 1 package cn.itcast.web.servlet;
 2 
 3 import javax.servlet.ServletException;
 4 import javax.servlet.annotation.WebServlet;
 5 import javax.servlet.http.Cookie;
 6 import javax.servlet.http.HttpServlet;
 7 import javax.servlet.http.HttpServletRequest;
 8 import javax.servlet.http.HttpServletResponse;
 9 import java.io.IOException;
10 import java.net.URLDecoder;
11 import java.net.URLEncoder;
12 importthe java.text.SimpleDateFormat;
 13 is  Import java.util.Date;
 14  
15 @WebServlet ( "/ CookieServlet" )
 16  public  class CookieServlet the extends the HttpServlet {
 . 17      protected  void the doPost (the HttpServletRequest Request, the HttpServletResponse Response) throws IOException {
 18 is          // Get PrintWriter and encoding data format of the stream before setting response message body 
. 19          response.setHeader ( "Content-type", "text / HTML; charset = UTF-. 8" );
 20 is  
21 is          // 1. get all the cookies 
22 is          cookies [] cookies = request.getCookies ();
23          boolean Flag = false ;    // no name is called lastTime cookie
 24-  
25          // 2. traverse the cookie array 
26          IF (Cookies =! Null ) {
 27              for (Cookie cookie: Cookies) {
 28                  IF (the Cookie.getName (). the equals ( "lastTime")) {   // is not the first access 
29                      In Flag = to true ;
 30  
31 is                      String value = cookie.getValue ();
 32                      value = URLDecoder.decode (value, "UTF-. 8");   // the URL decoding 
33                     . response.getWriter () write ( "Welcome back, your last access time is" + value);
 34  
35                      // The value of the cookie value to the login time, resend cookie 
36                      a Date DATE = new new a Date ();
 37 [                      the SimpleDateFormat SDF = new new the SimpleDateFormat ( "date YYYY, mM-dd HH: mm: SS" );
 38 is                      String str_date = sdf.format (dATE);
 39                      str_date = the URLEncoder.encode (str_date, "UTF-. 8" );     // URL encoding, since str_date contains a space, if no error will be URL-encoded 
40                      cookie.setValue (str_date);
 41 is                     cookie.setMaxAge (30 * 24 * 60 * 60 ); 　// set the cookie survival time
 42 is                      response.addCookie (cookie);
 43 is                      BREAK ;
 44 is                  }
 45              }
 46 is          }
 47  
48          IF (Cookies == null || In Flag == false ) {   // first visit 
49              response.getWriter () the Write ( "Hello <h1>, welcome to your first visit <h1>." );
 50  
51              a Date DATE = new new a Date ();
 52              SimpleDateFormat SDF = new new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
53             String str_date = sdf.format(date);
54             str_date = URLEncoder.encode(str_date, "utf-8");
55             Cookie cookie = new Cookie("lastTime", str_date);
56             cookie.setMaxAge(30 * 24 *60 *60);
57             response.addCookie(cookie);
58         }
59 
60 
61     }
62 
63     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
64         this.doPost(request, response);
65     }
66 }