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Javax.servlet.http.Sīkfailu klase Java

Daudzas vietnes izmanto nelielas teksta virknes, kas pazīstamas kā sīkfaili, lai saglabātu pastāvīgu klienta puses stāvokli starp savienojumiem. Sīkfaili tiek nosūtīti no servera uz klientu un atkal HTTP pieprasījumu un atbilžu galvenēs. Serveris var izmantot sīkfailus, lai norādītu sesijas ID, iepirkumu groza saturu, pieteikšanās akreditācijas datus, lietotāja preferences un citus.

Kā darbojas sīkfaili?

Kā sīkfaili darbojas?' title= Kā redzams no iepriekš redzamās diagrammas, kad lietotājs pirmo reizi pieprasa lapu, serveris kopā ar resursiem nosūta sīkfailu objektu, kas jāsaglabā klienta datorā. Šajā objektā var būt informācija par pieprasījumu. Tagad vēlāk, ja lietotājs atkārtoti pieprasa to pašu resursu, tas kopā ar pieprasījumu nosūta saglabāto sīkfailu, ko serveri var izmantot, lai vēl vairāk uzlabotu lietotāja pieredzi. Sīkdatņu atribūti:
    Vārds = vērtību pāris:Tas attēlo faktisko informāciju, kas tiek glabāta sīkfailā. Ne nosaukumā, ne vērtībā nedrīkst būt atstarpes vai kāda no šīm rakstzīmēm: [ ] ( ) = ' / ? @ : ; Derīga sīkfaila nosaukuma-vērtības pāra piemērs: 
     Set-Cookie:session-id = 187-4969589-3049309
    Domēns: By default a cookie applies to the server it came from. If a cookie is originally set by www.foo.example.com the browser will only send the cookie back to www.foo.example.com. However a site can also indicate that a cookie applies within an entire subdomain not just at the original server. For example this request sets a user cookie for the entire foo.example.com domain: The browser will echo this cookie back not just to www.foo.example.com but also to lothar.foo.example.com eliza.foo.example.com enoch.foo.example.com and any other host somewhere in the foo.example.com domain. However a server can only set cookies for domains it immediately belongs to. www.foo.example.com cannot set a cookie for www.geeksforgeeks.org example.com or .com no matter how it sets the domain. 
     Set-Cookie: user = geek ;Domain =.foo.example.com
    Ceļš: When requesting a document in the subtree from the same server the client echoes that cookie back. However it does not use the cookie in other directories on the site. 
    Set-Cookie: user = geek; Path =/ restricted
    Beidzas: The browser should remove the cookie from its cache after that date has passed. 
     Set-Cookie: user = geek; expires = Wed 21-Feb-2017 15:23:00 IST
    Maksimālais vecums: This attribute sets the cookie to expire after a certain number of seconds have passed instead of at a specific moment. For instance this cookie expires one hour (3600 seconds) after it’s first set. 
    Set-Cookie: user = 'geek'; Max-Age = 3600
Konstruktors : Creates a cookie with specified name-value pair. 
  Syntax :   public Cookie(String name String value)   Parameters :   name : name of the cookie value : value associated with this cookie
Metodes:
    setDomain() : Sets the domain in which this cookie is visible. Domains are explained in detail in the attributes of cookie part previously. 
      Syntax :   public void setDomain(String pattern)   Parameters :   pattern : string representing the domain in which this cookie is visible.
    getDomain() : Returns the domain in which this cookie is visible. 
      Syntax :   public String getDomain()
    setComment() : Specifies the purpose of this cookie. 
      Syntax :   public void setComment(String purpose)   Parameters :   purpose : string representing the purpose of this cookie.
    saņemt komentāru () : Returns the string representing purpose of this cookie. 
      Syntax :   public String getComment()
    setMaxAge() : Specifies the time (in seconds) elapsed before this cookie expires. 
      Syntax :   public void setMaxAge(long time)   Parameters :   time : time in seconds before this cookie expires
    getMaxAge() : Returns the max age component of this cookie. 
      Syntax :   public String getMaxAge()
    setPath() : Specifies a path for the cookie to which the client should return the cookie. 
      Syntax :   public void setPath(String path)   Parameters :   path : path where this cookie is returned
    getPath() : Returns the path component of this cookie. 
      Syntax :   public String getMaxAge()
    setSecure() : Indicated if secure protocol to be used while sending this cookie. Default value is false. 
      Syntax :   public void setSecure(boolean secure)   Parameters:   secure - If true the cookie can only be sent over a secure protocol like https. If false it can be sent over any protocol.
    getSecure() : Returns true if this cookie must be sent by a secure protocol otherwise false. 
      Syntax :   public boolean getSecure()
    getName() : Returns the name of the cookie. 
       Syntax :   public String getName()
    setValue() : Assigns new value to cookie after initialisation. 
      Syntax :   public void setValue(String newValue)   Parameters :   newValue - a String specifying the new value
    getValue: Returns the value of the cookie. 
      Syntax :   public String getValue()
    getVersion() : Returns 0 if the cookie complies with the original Netscape specification; 1 if the cookie complies with RFC 2965/2109 
      Syntax :   public int getVersion()
    setVersion() : Used to set the version of the cookie protocol this cookie uses. 
      Syntax :  public void setVersion(int v)   Parameters :   v - 0 for original Netscape specification; 1 for RFC 2965/2109
    klons () : returns a copy of this cookie. 
      Syntax :   public Cookie clone()
Below is a Java implementation of a simple servlet program which stores a cookie in the browser when user first requests for it and then for further requests it displays the cookies stored. Java 
// Java program to illustrate methods // of Cookie class import java.io.IOException; import java.io.PrintWriter; import java.util.List; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.Cookie; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; /**  * Servlet implementation class cookieTest  */ @WebServlet('/cookieTest') public class cookieTest extends HttpServlet  {  private static final long serialVersionUID = 1L;  /**  * @see HttpServlet#HttpServlet()  */  public cookieTest() {  super();  // TODO Auto-generated constructor stub  }  /**  * @see HttpServlet#doGet(HttpServletRequest request HttpServletResponse  * response)  */  protected void doGet(HttpServletRequest request HttpServletResponse response)  throws ServletException IOException   {  response.setContentType('text/html');  // Create a new cookie with the name test cookie  // and value 123  Cookie cookie = new Cookie('test_cookie' '123');  // setComment() method  cookie.setComment('Just for testing');  // setDomain() method  // cookie.setDomain('domain');  // setMaxAge() method  cookie.setMaxAge(3600);  // setPath() method  cookie.setPath('/articles');  // setSecure() method  cookie.setSecure(false);  // setValue() method  cookie.setValue('321');  // setVersion() method  cookie.setVersion(0);  response.addCookie(cookie);  PrintWriter pw = response.getWriter();  pw.print('  ');  Cookie ck[] = request.getCookies();  if (ck == null) {  pw.print('
This is first time the page is requested.
');  pw.print('
And therefore no cookies found
 

');  } else {  pw.print('
Welcome Again...Cookies found
');  for (int i = 0; i < ck.length; i++) {  // getName() method  pw.print('
Name :' + ck[i].getName() + '
');  // getValue() method  pw.print('
Value :' + ck[i].getValue() + '
');  // getDomain() method  pw.print('
Domain :' + ck[i].getDomain() + '
');  // getPath() method  pw.print('
Name :' + ck[i].getPath() + '
');  // getMaxAge() method  pw.print('
Max Age :' + ck[i].getMaxAge() + '
');  // getComment() method  pw.print('
Comment :' + ck[i].getComment() + '
');  // getSecure() method  pw.print('
Name :' + ck[i].getSecure() + '
');  // getVersion() method  pw.print('
Version :' + ck[i].getVersion() + '
');  }  pw.print('  ');  }  pw.close();  }  /**  * @see HttpServlet#doPost(HttpServletRequest request HttpServletResponse  * response)  */  protected void doPost(HttpServletRequest request HttpServletResponse response)  throws ServletException IOException   {    doGet(request response);  } }
IZEJA: Šāda izvade ir no tīmekļa pārlūkprogrammas- Pirmajam pieprasījumam: 
This is first time the page is requested. And therefore no cookies found.
Otrajam pieprasījumam: 
Welcome Again...Cookies found Name :test_cookie Value :321 Domain :null Name :null Max Age :-1 Comment :null Name :false Version :0

Kā palaist iepriekš minēto programmu?

Vispirms pārliecinieties, vai ir instalēts kāds serveris, piemēram, Apache Tomcat, un tas ir konfigurēts ar izmantoto rīku, piemēram, Eclipse. Vienkārši palaidiet iepriekš minēto programmu serverī vai vietējā pārlūkprogrammā, ievietojot pilnu izmantotā servera direktorija adresi. CookieTest servlets ir servlets, kas veic trīs uzdevumus:
  1. Vispirms servlets iestata sīkfailu ar nosaukumu test_cookie. Citas programmas rindas nosaka sīkfaila atribūtus, piemēram, maksimālo vecuma domēna vērtību utt.
  2. Otrkārt, servlet izmanto request.getCookies, lai atrastu visus ienākošos sīkfailus un parādītu to nosaukumus un citus atbilstošos atribūtus.
  3. Ja sīkfaili netiek atrasti, kā tas ir pirmā pieprasījuma gadījumā, tiek parādīts vienkāršs displeja ziņojums, kas norāda, ka tas ir pirmais lapas apmeklējums.
Atsauce: Oficiālā Java dokumentācija Izveidojiet viktorīnu