Cookie operation of 04_web Foundation ()

30, 31, 32, cookie operation:

1): Create a cookie and set up shared data:
Cookie C = new Cookie (String name,string value);
Cookie C = new Cookie ("Curreentname", "Wuji");
2): Put the cookie into the response, the shared data of the cookie is passed to the browser and saved by the browser.
Response object. Addcookie (c);
3): Obtain data from cookies and cookies. (obtained from the request)

4): The name and value of the cookie do not support Chinese.
Solution: Encode and decode the Chinese language.
Put
String msg= "Hello";
String encode = Urlencoder.encode (msg, "UTF-8");
System.out.println (encode);
Cookie C2 = new Cookie ("CurreentName2", encode);
Take:
String name = Cookie.getname ();
String value = Cookie.getvalue ();
String decode = Urldecoder.decode (value, "UTF-8");

5): Change the value of the specified name of the cookie.
Mode 1: Gets the modified cookie object according to the name, just call the SetValue method.
Mode 2: Recreate a cookie with the same name.

Note: After modifying, you call the Response object. Addcookie (c);

6): The life cycle of the cookie: (How long the shared data in the cookie can be retained)
By default: Closing the browser cookie is lost.
Setmaxage (int seconds) of the cookie object: How long the cookie can be set to survive.
Seconds>0: How many seconds can be survived.
seconds<0: stored in the browser process, closed browser cookie is lost.
Seconds=0: Delete cookies.
7): Delete cookies:
Cookie object. setmaxage (0);
8): The cookie is defective. (emphasis in the focus)
1&gt: Chinese handling trouble.
2&gt: Multiple people sharing the same computer, information is not secure.
3>: A cookie can store only one simple type of data.
To store, account, password, mail, etc. at the same time.
The main reason is that the value of a cookie can only store string and cannot save object.
4>:cookie size and quantity limits:
The cookie size limit is within 4KB;
* A server holds a maximum of 20 cookies on a client;
* A browser can hold up to 300 cookies;
The 5>:cookie principle: Store shared data in a browser.
Each request, and then bring the shared data to the server.

Code:

1  PackageCom.day07.web.demo2.controller;2 3 Importjavax.servlet.ServletException;4 ImportJavax.servlet.annotation.WebServlet;5 ImportJavax.servlet.http.Cookie;6 ImportJavax.servlet.http.HttpServlet;7 Importjavax.servlet.http.HttpServletRequest;8 ImportJavax.servlet.http.HttpServletResponse;9 Importjava.io.IOException;Ten ImportJava.io.PrintWriter; One  A /** - * Created by Administrator on 2017/12/7. -  */ the@WebServlet ("/cookie") -  Public classCookieservletextendsHttpServlet { - @Override -      Public voidService (HttpServletRequest req, HttpServletResponse resp)throwsservletexception, IOException { +         //Request garbled processing -Req.setcharacterencoding ("Utf-8"); +         //Response garbled processing AResp.setcontenttype ("Text/html;charset=utf-8"); at         //Manipulating Cookies -  -         //Increase -Cookie Cookie1 =NewCookie ("Name1", "Wuji1"); - Resp.addcookie (cookie1); -Cookie Cookie2 =NewCookie ("Name2", "Wuji2"); in Resp.addcookie (cookie2); -         //Delete to        /*6): The life cycle of the cookie: (How long the shared data in the cookie can be retained) + By default: Closing the browser cookie is lost. - setmaxage (int seconds) of the cookie object: How long the cookie can be set to survive. the seconds>0: How many seconds can be survived. * seconds<0: stored in the browser process, closed browser cookie is lost. $ seconds=0: Delete cookies.Panax Notoginseng 7): Delete cookies: - Cookie object. setmaxage (0);*/ theCookie1.setmaxage (0); +         //must be Resp.addcookie (cookie) before it can take effect A Resp.addcookie (cookie1); the         //Modify +  -         //Enquiry $  $         //get Output Object -PrintWriter writer =Resp.getwriter (); -         //Output Information theWriter.println ("Hello sister!")); - Wuyi  the     } -}

Cookieservlet

1  PackageCom.day07.web.demo2.controller;2 3 Importjavax.servlet.ServletException;4 ImportJavax.servlet.annotation.WebServlet;5 ImportJavax.servlet.http.Cookie;6 ImportJavax.servlet.http.HttpServlet;7 Importjavax.servlet.http.HttpServletRequest;8 ImportJavax.servlet.http.HttpServletResponse;9 Importjava.io.IOException;Ten ImportJava.io.PrintWriter; One  A /** - * Created by Administrator on 2017/12/7. -  */ the@WebServlet ("/cookie2") -  Public classCookie2servletextendsHttpServlet { - @Override -      Public voidService (HttpServletRequest req, HttpServletResponse resp)throwsservletexception, IOException { +         //Request garbled processing -Req.setcharacterencoding ("Utf-8"); +         //Response garbled processing AResp.setcontenttype ("Text/html;charset=utf-8"); at         //Manipulating Cookies -  -         //Delete -         //Modify -  -         //Enquiry incookie[] Cookies =req.getcookies (); -          for(inti=0;i<cookies.length;i++){ toCookie cookie =Cookies[i]; +             //take key -String name =cookie.getname (); the             //Take value *String value =Cookie.getvalue (); $             //PrintPanax NotoginsengSystem.out.println (name+ "=" +value); -  theCookie.setvalue ("Zhaoming"); + Resp.addcookie (cookie); A         } the  +         //get Output Object -PrintWriter writer =Resp.getwriter (); $         //Output Information $Writer.println ("Hello sister----get cookie data!")); -  -  the     } -}

Cookie2servlet

Cookie operation of 04_web Foundation ()