org.apache.juneau.http.Via Maven / Gradle / Ivy
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package org.apache.juneau.http;
/**
* Represents a parsed Via HTTP response header.
*
*
* Informs the client of proxies through which the response was sent.
*
*
Example
*
* Via: 1.0 fred, 1.1 example.com (Apache/1.1)
*
*
*
* Informs the client of proxies through which the response was sent.
*
*
*
Example
*
* Via: 1.0 fred, 1.1 example.com (Apache/1.1)
*
*
*
*
RFC2616 Specification
*
* The Via general-header field MUST be used by gateways and proxies to indicate the intermediate protocols and
* recipients between the user agent and the server on requests, and between the origin server and the client on
* responses.
* It is analogous to the "Received" field of RFC 822 and is intended to be used for tracking message forwards,
* avoiding request loops, and identifying the protocol capabilities of all senders along the request/response chain.
*
*
* Via = "Via" ":" 1#( received-protocol received-by [ comment ] )
* received-protocol = [ protocol-name "/" ] protocol-version
* protocol-name = token
* protocol-version = token
* received-by = ( host [ ":" port ] ) | pseudonym
* pseudonym = token
*
*
*
* The received-protocol indicates the protocol version of the message received by the server or client along each
* segment of the request/response chain.
* The received-protocol version is appended to the Via field value when the message is forwarded so that information
* about the protocol capabilities of upstream applications remains visible to all recipients.
*
*
* The protocol-name is optional if and only if it would be "HTTP".
* The received-by field is normally the host and optional port number of a recipient server or client that subsequently
* forwarded the message.
* However, if the real host is considered to be sensitive information, it MAY be replaced by a pseudonym.
* If the port is not given, it MAY be assumed to be the default port of the received-protocol.
*
*
* Multiple Via field values represents each proxy or gateway that has forwarded the message.
* Each recipient MUST append its information such that the end result is ordered according to the sequence of
* forwarding applications.
*
*
* Comments MAY be used in the Via header field to identify the software of the recipient proxy or gateway, analogous
* to the User-Agent and Server header fields.
* However, all comments in the Via field are optional and MAY be removed by any recipient prior to forwarding the
* message.
*
*
* For example, a request message could be sent from an HTTP/1.0 user agent to an internal proxy code-named "fred",
* which uses HTTP/1.1 to forward the request to a public proxy at nowhere.com, which completes the request by
* forwarding it to the origin server at www.ics.uci.edu.
* The request received by www.ics.uci.edu would then have the following Via header field:
*
* Via: 1.0 fred, 1.1 nowhere.com (Apache/1.1)
*
*
*
* Proxies and gateways used as a portal through a network firewall SHOULD NOT, by default, forward the names and ports
* of hosts within the firewall region.
* This information SHOULD only be propagated if explicitly enabled.
* If not enabled, the received-by host of any host behind the firewall SHOULD be replaced by an appropriate pseudonym
* for that host.
*
*
* For organizations that have strong privacy requirements for hiding internal structures, a proxy MAY combine an
* ordered subsequence of Via header field entries with identical received-protocol values into a single such entry.
* For example...
*
* Via: 1.0 ricky, 1.1 ethel, 1.1 fred, 1.0 lucy
*
*
*
* ...could be collapsed to...
*
* Via: 1.0 ricky, 1.1 mertz, 1.0 lucy
*
*
*
* Applications SHOULD NOT combine multiple entries unless they are all under the same organizational control and the
* hosts have already been replaced by pseudonyms.
* Applications MUST NOT combine entries which have different received-protocol values.
*
*
Additional Information
*
*/
public final class Via extends HeaderStringArray {
/**
* Returns a parsed Via header.
*
* @param value The Via header string.
* @return The parsed Via header, or null if the string was null.
*/
public static Via forString(String value) {
if (value == null)
return null;
return new Via(value);
}
private Via(String value) {
super(value);
}
}