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package org.apache.juneau.http;

import org.apache.juneau.http.annotation.*;

/**
 * Represents a parsed <l>Authorization</l> HTTP request header.
 *
 * <p>
 * Authentication credentials for HTTP authentication.
 *
 * <h5 class='figure'>Example</h5>
 * <p class='bcode w800'>
 *    Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==
 * </p>
 *
 * <h5 class='topic'>RFC2616 Specification</h5>
 *
 * A user agent that wishes to authenticate itself with a server--usually, but not necessarily, after receiving a 401
 * response--does so by including an Authorization request-header field with the request.
 *
 * <p>
 * The Authorization field value consists of credentials containing the authentication information of the user agent for
 * the realm of the resource being requested.
 *
 * <p class='bcode w800'>
 *    Authorization  = "Authorization" ":" credentials
 * </p>
 *
 * <p>
 * HTTP access authentication is described in "HTTP Authentication: Basic and Digest Access Authentication".
 *
 * <p>
 * If a request is authenticated and a realm specified, the same credentials SHOULD be valid for all other requests
 * within this realm (assuming that the authentication scheme itself does not require otherwise, such as credentials
 * that vary according to a challenge value or using synchronized clocks).
 *
 * <p>
 * When a shared cache (see section 13.7) receives a request containing an Authorization field, it MUST NOT return the
 * corresponding response as a reply to any other request, unless one of the following specific exceptions holds:
 * <ol>
 *    <li>If the response includes the "s-maxage" cache-control directive, the cache MAY use that response in replying
 *       to a subsequent request.
 *       But (if the specified maximum age has passed) a proxy cache MUST first revalidate it with the origin
 *       server, using the request-headers from the new request to allow the origin server to authenticate the new
 *       request.
 *       (This is the defined behavior for s-maxage.)
 *       If the response includes "s-maxage=0", the proxy MUST always revalidate it before re-using it.
 *    <li>If the response includes the "must-revalidate" cache-control directive, the cache MAY use that response in
 *       replying to a subsequent request.
 *       But if the response is stale, all caches MUST first revalidate it with the origin server, using the
 *       request-headers from the new request to allow the origin server to authenticate the new request.
 *    <li>If the response includes the "public" cache-control directive, it MAY be returned in reply to any subsequent
 *       request.
 * </ol>
 *
 * <h5 class='section'>See Also:</h5>
 * <ul class='doctree'>
 *    <li class='extlink'>{@doc RFC2616}
 * </ul>
 */
@Header("Authorization")
public final class Authorization extends HeaderString {

   /**
    * Returns a parsed <code>Authorization</code> header.
    *
    * @param value The <code>Authorization</code> header string.
    * @return The parsed <code>Authorization</code> header, or <jk>null</jk> if the string was null.
    */
   public static Authorization forString(String value) {
      if (value == null)
         return null;
      return new Authorization(value);
   }

   private Authorization(String value) {
      super(value);
   }
}