Cookie

Set cookie

 Cookie cookie = new Cookie("name","abc"); //new Cookie(String,String)
 cookie.setMaxAge(1000); 
 //in seconds, default if not set: cleaned when browser closed
 response.addCookie(cookie); //remember to call addCookie

Get cookie

//Have to get all cookies as Array, then loop through each of them

Cookie cookies[] = request.getCookies(); //return null if none cookies
for(int i=0;i&ltcookies.length;i++){
 Cookie cookie = cookies[i];
 cookie.getName();
 cookie.getValue();
 cookie.getMaxAge();
}

• Multiple browsers can share the same cookie 
• If set the same key word, the old value will be replaced 
• Every cookie can have their own life length 
• All cookie from the same webapp will store in one single file on client hard drive, with timestamp
• 20 most cookies a webapp can save to browser, each cookie have 4k max space
• a browser can save 300 most cookies

Cookie life cycle

• Cookie by default, will be destroyed when browser closed
• setMaxAge(1000) can set length of life time for cookie
• setMaxAge(0) destroy cookie
• setMaxAge(-1000) cookie will destroy when browser closed

Cookie with Different Character set

  Saving

String val = java.net.URLEncoder.encode("中国字","utf-8");
Cookie cookie = new Cookie("name",val);

Getting

  String val = java.net.URLDecoder.decode(cookie.getValue(),"utf-8");