Servlet Cookie processing
Cookie is stored on the client computer on the text file , and retain a variety of tracking information . Apparently Java Servlet support HTTP Cookie .
Returns the user identification comprises three steps:
- Server scripts to the browser sends a group of Cookie. For example: name, age or identification number.
- Browser this information is stored on the local computer for future use.
- When the next time the browser to the Web server transmits any request, the browser will the Cookie information is sent to the server, the server will use this information to identify the user.
This chapter will explain You how to set or reset Cookie , how to access them, and how they are deleted .
// the Servlet needs to process cookies Chinese encoding and decoding, as follows: String STR = java.net.URLEncoder.encode ( "Chinese", "UTF-. 8"); // encoding Encoder String STR = java.net.URLDecoder .decode ( "encoded string", "UTF-. 8"); // decode decoder
Cookie analysis
Cookie is usually set in the HTTP header information in (although JavaScript can also be set directly in a browser Cookie). Set Cookie Servlet sends the header information following:
<! - the Set-cookies header contains: a name value pair; a GMT date; a path; domain -> <! - name and URL value will be encoded. -> ! <- the Expires field is an instruction that tells the browser after a given period of time and date "forget" the Cookie. -> HTTP / 1.1 200 the OK a Date: Fri, 04 Feb 2000 21:03:38 GMT Server: the Apache / 1.3.9 (UNIX) PHP / 4.0b3 the Set-Cookie: name = xyz; the Expires = catalog on Friday, 04-Feb-07 22:03:38 GMT; path = /; Domain = runoob.com Connection: use Close Content-Type: text / HTML
If your browser is configured to store Cookie, it will retain this information until the expiration date.
If the user's browser to point to any match of the Cookie path and domain of the page , it will re-send Cookie to the server.
Browser header information may be as follows:
GET / HTTP/1.0
Connection: Keep-Alive
User-Agent: Mozilla/4.6 (X11; I; Linux 2.2.6-15apmac ppc)
Host: zink.demon.co.uk:1126
Accept: image/gif, */*
Accept-Encoding: gzip
Accept-Language: en
Accept-Charset: iso-8859-1,*,utf-8
Cookie: name=xyz
Servlet can by request method request.getCookies () to access Cookie, the method returns a Cookie object array .
Servlet Cookie method
The following is the Servlet Cookie operations useful to use in the list of methods .
| 序号 | 方法 & 描述 |
|---|---|
| 1 | public void setDomain(String pattern) 该方法设置 cookie 适用的域，例如 runoob.com。 |
| 2 | public String getDomain() 该方法获取 cookie 适用的域，例如 runoob.com。 |
| 3 | public void setMaxAge(int expiry) 该方法设置 cookie 过期的时间（以秒为单位）。如果不这样设置，cookie 只会在当前 session 会话中持续有效。 |
| 4 | public int getMaxAge() 该方法返回 cookie 的最大生存周期（以秒为单位），默认情况下，-1 表示 cookie 将持续下去，直到浏览器关闭。 |
| 5 | public String getName() 该方法返回 cookie 的名称。名称在创建后不能改变。 |
| 6 | public void setValue(String newValue) 该方法设置与 cookie 关联的值。 |
| 7 | public String getValue() 该方法获取与 cookie 关联的值。 |
| 8 | public void setPath(String uri) 该方法设置 cookie 适用的路径。如果您不指定路径，与当前页面相同目录下的（包括子目录下的）所有 URL 都会返回 cookie。 |
| 9 | public String getPath() 该方法获取 cookie 适用的路径。 |
| 10 | public void setSecure(boolean flag) 该方法设置布尔值，表示 cookie 是否应该只在加密的（即 SSL）连接上发送。 |
| 11 | public void setComment(String purpose) 设置cookie的注释。该注释在浏览器向用户呈现 cookie 时非常有用。 |
| 12 | public String getComment() 获取 cookie 的注释，如果 cookie 没有注释则返回 null。 |
Cookie settings by Servlet
(1) create a Cookie object:
// call the Cookie constructor with a cookie name and cookie value // cookie name and cookie value are strings. The cookie Cookie = new new Cookie ( "Key", "value");
(2) set the maximum life cycle:
// use the method to specify setMaxAge cookie, capable of maintaining effective period of time (in seconds). // The following sets a maximum validity period of 24 hours cookie. cookie.setMaxAge ( 60 * 60 * 24);
(3) transmits a response to the HTTP Cookie header:
// add the HTTP response header using Cookie response.addCookie response.addCookie (Cookie);
Cookie read by Servlet
Delete Cookie by Servlet
Delete Cookie is very simple. If you want to delete a cookie, you only need to follow these three steps:
- Read an existing cookie, and it is stored in the Cookie object.
- Use setMaxAge () method to set the cookie age of zero to delete an existing cookie.
- This cookie added to the response headers .