Java's cookie to remember user login time Case

demand:

　　1. Visit 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

analysis:

1 . Cookie can be accomplished using
 2 in the server Servlet determine whether there is a cookie called the lastTime. 
    2. 1 are: not the first visit to
           1. Response data: Welcome back, your last visit time: 2019 October 4 11:50:20 
          2. write back Cookie: lastTime = 2019 Nian October 4 11:50:01 
    2.2 is not: It is the first visit to
           a response data: Hello, welcome to your first visit
           2. write back Cookie: lastTime = 2019 Nian 10 Yue 4 Ri 11:50:01

 

Code:

  1 import javax.servlet.ServletException;
  2 import javax.servlet.annotation.WebServlet;
  3 import javax.servlet.http.Cookie;
  4 import javax.servlet.http.HttpServlet;
  5 import javax.servlet.http.HttpServletRequest;
  6 import javax.servlet.http.HttpServletResponse;
  7 import java.io.IOException;
  8 import java.net.URLDecoder;
  9 import java.net.URLEncoder;
 10 import java.text.SimpleDateFormat;
 11 import java.util.Date;
12 is  
13 is  / ** 
14     remember the user login time Case
 15   * / 
16 @WebServlet ( "/ CookieServlet" )
 . 17  public  class CookieServlet the extends the HttpServlet {
 18 is      protected  void the doPost (the HttpServletRequest Request, the HttpServletResponse Response) throws ServletException, IOException {
 . 19          // Setup response message body formats, and encoded data 
20 is          the response.setContentType ( "text / HTML; charset = UTF-. 8" );
 21 is  
22 is          // . 1 accessories Cookie 
23 is          cookies [] = cookies request.getCookies ();
24          Boolean In Flag = to false ;   // default is no cookie lastTime
 25          // 2. cookie traverse the array 
26 is          IF (= Cookies! Null && cookies.length> 0 {)
 27              for (cookie cookies: Cookies) {
 28                  // . 3 acquires All cookie names 
29                  String name = the Cookie.getName ();
 30                  // 4. determines whether the name is lastTime 
31 is                  iF ( "lastTime" .equals (name)) {
 32                      // there cookie, not the first access 
33 is                      in Flag = to true ;
34 is  
35                      // Get the cookie value
 36                      // response data
 37                      // Get the cookie value, s time 
38 is                      String value = cookie.getValue ();
 39  
40                      System.out.println ( "before decoding:" + value);
 41 is                      // the URL decoder 
42 is                      value URLDecoder.decode = (value, "UTF-. 8" );
 43 is                      System.out.println ( "decoded:" + value);
 44 is  
45  
46 is                      // set the cookie value
 47                      // Get string current time, reset the cookie value, re-send cookie 
48 
 49                     Date date = new Date();
 50                     SimpleDateFormat sdf = new SimpleDateFormat("yyyy年MM月dd日 HH:mm:ss");
 51                     String str_date = sdf.format(date);
 52 
 53                     System.out.println("编码前："+str_date);
 54                     //URL 编码
 55                     str_date = URLEncoder.encode(str_date, "utf-8");
 56                     System.out.println("编码后："+str_date);
 57 
 58                     cookie.setValue(str_date);
 59 
 60                     // set the cookie survival time of 
61                      cookie.setMaxAge (60 * 60 );
 62                      response.addCookie (cookie);
 63  
64-  
65                      response.getWriter () the Write ( "<h1> Welcome back, your last visit time: "+ value +" </ h1 of> " );
 66  
67                      BREAK ;
 68                  }
 69              }
 70          }
 71 is  
72          IF (Cookies == null || cookies.length == == 0 || In Flag to false ) {
 73 is              // not, first visit
 74  
75              //Set the cookie value
 76              // get the current time string set cookie value, transmits cookie 
77  
78              a Date DATE = new new a Date ();
 79              the SimpleDateFormat SDF = new new the SimpleDateFormat ( "date YYYY, MM-dd HH: mm: ss" );
 80              String str_date = sdf.format (DATE);
 81              Cookie the cookie = new new Cookie ( "lastTime" , str_date);
 82  
83              // resolution time there are special characters using the URL encoding 
84              System.out.println ( "coding ago: "+ str_date);
 85              // the URL of encoding 
86             = the URLEncoder.encode str_date (str_date, "UTF-. 8" );
 87              System.out.println ( "encoded:" + str_date);
 88  
89              cookie.setValue (str_date);
 90  
91 is              // set the cookie survival time of 
92              cookie.setMaxAge (60 * 60 );
 93              response.addCookie (Cookie);
 94  
95              . response.getWriter () Write ( "<h1 of> Welcome you first access </ h1 of>" );
 96          }
 97      }
 98  
99      protected  void doGet (Request the HttpServletRequest, HttpServletResponse the Response) throws ServletException, IOException {
100         this.doPost(request, response);
101     }
102 }