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Javax.servlet.http.Cookie-klasse i Java

Mange websteder bruger små tekststrenge kendt som cookies til at gemme vedvarende klientsidetilstand mellem forbindelser. Cookies sendes fra server til klient og tilbage igen i HTTP-headerne for anmodninger og svar. Cookies kan bruges af en server til at angive sessions-id'er indkøbskurvs indhold login-legitimationsoplysninger brugerpræferencer og mere.

Hvordan fungerer cookies?

Hvordan fungerer cookies?' title= Som det ses af ovenstående diagram, når en bruger første gang anmoder om en side, sender serveren sammen med ressourcen et cookieobjekt, der skal gemmes på klientens maskine. Dette objekt kan indeholde detaljer om anmodningen. Nu senere, hvis brugeren igen anmoder om den samme ressource, sender den sammen med anmodningen den cookie, som kan bruges af servere til yderligere at forbedre brugerens oplevelse. Cookies egenskaber:
    Navn = værdipar:Dette viser de faktiske oplysninger, der er gemt i cookien. Hverken navnet eller værdien må indeholde mellemrum eller nogen af ​​følgende tegn: [ ] ( ) = ' / ? @ : ; Eksempel på gyldigt cookienavn-værdi-par: 
     Set-Cookie:session-id = 187-4969589-3049309
    Domæne: 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
    Sti: 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
    Udløber: 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
    Max-alder: 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
Konstruktør : 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
Metoder:
    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.
    getComment() : 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
    clone(): 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() + '
dobbelt i java

');  }  pw.print('  ');  }  pw.close();  }  /**  * @see HttpServlet#doPost(HttpServletRequest request HttpServletResponse  * response)  */  protected void doPost(HttpServletRequest request HttpServletResponse response)  throws ServletException IOException   {    doGet(request response);  } }
PRODUKTION: Følgende output er fra en webbrowser- For den første anmodning: 
This is first time the page is requested. And therefore no cookies found.
For den anden anmodning: 
Welcome Again...Cookies found Name :test_cookie Value :321 Domain :null Name :null Max Age :-1 Comment :null Name :false Version :0

Hvordan kører man ovenstående program?

Sørg først for, at du har en server som Apache Tomcat installeret og er konfigureret med det værktøj, du bruger, som Eclipse. Kør blot ovenstående program på serveren eller på din lokale browser ved at indsætte den fulde adresse på det serverbibliotek, du bruger. CookieTest-servleten er en servlet, der udfører tre opgaver:
  1. Først sætter servlet en cookie med navnet test_cookie. Andre linjer i programmet indstiller cookiens attributter, såsom maks. aldersdomæneværdi osv.
  2. For det andet bruger servlet'en request.getCookies til at finde alle de indgående cookies og vise deres navne og andre tilsvarende attributter.
  3. Hvis der ikke findes cookies, som det var tilfældet med den første anmodning, vises en simpel displaymeddelelse, som fortæller, at det er det første besøg på siden.
Reference: Officiel Java-dokumentation Opret quiz