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GET /pub/WWW/ HTTP/1.1 Host: www.w3.org in Java Make pdf417 in Java GET /pub/WWW/ HTTP/1.1 Host: www.w3.org aspx.net DataMatrix

GET /pub/WWW/ HTTP/1.1 Host: www.w3.org using barcode integrating for none control to generate, create none image in none applications.creating data matrix asp.net A client MUST include a H none for none ost header field in all HTTP/1.1 request messages. If the requested URI does not include an Internet host name for the service being requested, then the Host header field MUST be given with an empty value.

An HTTP/1.1 proxy MUST ensure that any request message it forwards does contain an appropriate Host header field that identifies the service being requested by the proxy. All Internet-based HTTP/1.

1 servers MUST respond with a 400 (Bad Request) status code to any HTTP/1.1 request message which lacks a Host header field. See sections 5.

2 and 19.6.1.

1 for other requirements relating to Host.. QR Code Spevcification 14.24 If-Match The If-Match request-head none for none er field is used with a method to make it conditional. A client that has one or more entities previously obtained from the resource can verify that one of those entities is current by including a list of their associated entity tags in the If-Match header field. Entity tags are defined in section 3.

11. The purpose of this feature is to allow efficient updates of cached information with a minimum amount of transaction overhead. It is also used, on updating requests, to prevent inadvertent modification of the wrong version of a resource.

As a special case, the value * matches any current entity of the resource.. If-Match = "If-Match" ":" ( "*" . 1#entity-tag ). If any of the entity tags match the entity tag of the entity that would have been returned in the response to a similar GET request (without the If-Match header) on that resource, or if * is given and any current entity exists for that resource, then the server MAY perform the requested method as if the If-Match header field did not exist.. Appendix C Hypertext Tr none for none ansfer Protocol: HTTP/1.1. A server MUST use the str ong comparison function (see section 13.3.3) to compare the entity tags in If-Match.

If none of the entity tags match, or if * is given and no current entity exists, the server MUST NOT perform the requested method, and MUST return a 412 (Precondition Failed) response. This behavior is most useful when the client wants to prevent an updating method, such as PUT, from modifying a resource that has changed since the client last retrieved it. If the request would, without the If-Match header field, result in anything other than a 2xx or 412 status, then the If-Match header MUST be ignored.

The meaning of If-Match: * is that the method SHOULD be performed if the representation selected by the origin server (or by a cache, possibly using the Vary mechanism; see section 14.44) exists, and MUST NOT be performed if the representation does not exist. A request intended to update a resource (e.

g., a PUT) MAY include an If-Match header field to signal that the request method MUST NOT be applied if the entity corresponding to the If-Match value (a single entity tag) is no longer a representation of that resource. This allows the user to indicate that they do not wish the request to be successful if the resource has been changed without their knowledge.

Examples:. If-Match: "xyzzy" If-Matc none for none h: "xyzzy", "r2d2xxxx", "c3piozzzz" If-Match: *. The result of a request h aving both an If-Match header field and either an If-NoneMatch or an If-Modified-Since header field is undefined by this specification.. 14.25 If-Modified-Since The If-Modified-Since req uest-header field is used with a method to make it conditional: If the requested variant has not been modified since the time specified in this field, an entity will not be returned from the server; instead, a 304 (not modified) response will be returned without any message-body.. If-Modified-Since = "If-Modified-Since" ":" HTTP-date An example of the field is If-Modified-Since: Sat, 29 Oct 1994 19:43:31 GMT Hypertext Transfer Protoc ol: HTTP/1.1. A GET method with an If-M none none odified-Since header and no Range header requests that the identified entity be transferred only if it has been modified since the date given by the If-Modified-Since header. The algorithm for determining this includes the following cases: (a) If the request would normally result in anything other than a 200 (OK) status, or if the passed If-Modified-Since date is invalid, the response is exactly the same as for a normal GET. A date which is later than the server s current time is invalid.

(b) If the variant has been modified since the If-Modified-Since date, the response is exactly the same as for a normal GET. (c) If the variant has not been modified since a valid If-Modified-Since date, the server SHOULD return a 304 (Not Modified) response. The purpose of this feature is to allow efficient updates of cached information with a minimum amount of transaction overhead.

Note: The Range request-header field modifies the meaning of If-ModifiedSince; see section 14.35 for full details. Note: If-Modified-Since times are interpreted by the server, whose clock might not be synchronized with the client.

Note: When handling an If-Modified-Since header field, some servers will use an exact date comparison function, rather than a less-than function, for deciding whether to send a 304 (Not Modified) response. To get the best results when sending an If-Modified-Since header field for cache validation, clients are advised to use the exact date string received in a previous Last-Modified header field whenever possible. Note: If a client uses an arbitrary date in the If-Modified-Since header instead of a date taken from the Last-Modified header for the same request, the client should be aware of the fact that this date is interpreted in the server s understanding of time.

The client should consider unsynchronized clocks and rounding problems due to the different encodings of time between the client and server. This includes the possibility of race conditions if the document has changed between the time it was first requested and the If-Modified-Since date of a subsequent request, and the possibility of clock-skew-related problems if the If-Modified-Since date is derived from the client s clock without correction. Appendix C Hypertext Transfer Protocol: HTTP/1.1. to the server s clock. none for none Corrections for different time bases between client and server are at best approximate due to network latency. The result of a request having both an If-Modified-Since header field and either an If-Match or an If-Unmodified-Since header field is undefined by this specification.

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