org.apache.juneau.http.Pragma Maven / Gradle / Ivy
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package org.apache.juneau.http;
/**
* Represents a parsed Pragma HTTP request/response header.
*
*
* Implementation-specific fields that may have various effects anywhere along the request-response chain.
*
*
Example
*
* Pragma: no-cache
*
*
* RFC2616 Specification
*
* The Pragma general-header field is used to include implementation- specific directives that might apply to any
* recipient along the request/response chain.
* All pragma directives specify optional behavior from the viewpoint of the protocol; however, some systems MAY
* require that behavior be consistent with the directives.
*
*
* Pragma = "Pragma" ":" 1#pragma-directive
* pragma-directive = "no-cache" | extension-pragma
* extension-pragma = token [ "=" ( token | quoted-string ) ]
*
*
*
* When the no-cache directive is present in a request message, an application SHOULD forward the request toward the
* origin server even if it has a cached copy of what is being requested.
* This pragma directive has the same semantics as the no-cache cache-directive (see section 14.9) and is defined here
* for backward compatibility with HTTP/1.0.
* Clients SHOULD include both header fields when a no-cache request is sent to a server not known to be HTTP/1.1
* compliant.
*
*
* Pragma directives MUST be passed through by a proxy or gateway application, regardless of their significance to that
* application, since the directives might be applicable to all recipients along the request/response chain.
* It is not possible to specify a pragma for a specific recipient; however, any pragma directive not relevant to a
* recipient SHOULD be ignored by that recipient.
*
*
* HTTP/1.1 caches SHOULD treat "Pragma: no-cache" as if the client had sent "Cache-Control: no-cache".
* No new Pragma directives will be defined in HTTP.
*
*
* Note: because the meaning of "Pragma: no-cache as a response header field is not actually specified, it does not
* provide a reliable replacement for "Cache-Control: no-cache" in a response.
*
*
Additional Information
*
*/
public final class Pragma extends HeaderString {
/**
* Returns a parsed Pragma header.
*
* @param value The Pragma header string.
* @return The parsed Pragma header, or null if the string was null.
*/
public static Pragma forString(String value) {
if (value == null)
return null;
return new Pragma(value);
}
private Pragma(String value) {
super(value);
}
}