21 Feb 2014

HTTP Request Headers I (Headers only)

Headers:

1. Accept:-

- This header specifies the MIME types that the browser or other clients can handle.

- A servlet that can return a resource in more than one format can examine the Accept header to decide which format to use.

Ex - request.getHeader ("Accept");

2. Accept- Charest:-

- This header indicates the character sets the browser can use.

Ex - request.getHeader ("Accept-Charest");

3. Authorization:-

- This header is used by clients to identify themselves when accessing password-protected Web pages.

4. Connection:-

- This header indicates whether the client can handle persistent HTTP connections. Persistent connections permit the client or other browser to retrieve multiple files with a single socket Connection.

5. Cookie:-

- This header returns cookies to servers that previously sent them to the browser.

Ex- request.getHeader ("Accept-Charest");

6. Host:-

- This header indicates the host and port as given in the original URL.

Ex- request.getHeader ("Host");

7. Referer:-

- This header indicates the URL of the referring Web page.

Ex- request.getHeader ("Referer");

8. Accept-Language:-

- This header specifies the client's preferred languages in case the servlet can produce results in more than one language.

- The value of the header should be one of the standard language codes such as en, en-us, da, etc.

9. If-Modified-Since:-

- This header indicates that the client wants the page only if it has been changed after the specified date.

- The server sends a 304 (Not Modified) header if no newer result is available.

Ex- request.getHeader ("If-Modified-Since");

10. If-Unmodified-Since:-

- This header is the reverse of If-Modified-Since it specifies that the operation should succeed only if the document is older than the specified date.

Ex- request.getHeader ("If-Unmodified-Since");

11. User-Agent:-

- This header identifies the browser or other client making the request and can be used to return different content to different types of browsers.

- However, the User-Agent header is quite useful for distinguishing among different categories of client.

- For example, Japanese developers might see whether the User-Agent is an Imode cell phone, a Skynet cell phone, or a Web browser.

Ex- request.getHeader ("User-Agent");

12. Accept-Encoding:-

- Using an encoding the browser doesn't understand results in incomprehensible pages.

- Consequently, it is critical that you explicitly check the Accept-Encoding header before using any type of content encoding.

- Values of gzip or compress are the two most common possibilities.

13. Content-Length:-

- This header is applicable only to POST requests and gives the size of the POST data in bytes.