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31  package org.apache.commons.httpclient.auth;
32  
33  import org.apache.commons.httpclient.Credentials;
34  
35  /**
36   * <p>
37   * Credentials provider interface can be used to provide {@link 
38   * org.apache.commons.httpclient.HttpMethod HTTP method} with a means to request
39   * authentication credentials if no credentials have been given or given
40   * credentials are incorrect.
41   * </p>
42   * <p>
43   * HttpClient makes no provisions to check whether the same credentials have
44   * been tried already. It is a responsibility of the custom credentials provider
45   * to keep track of authentication attempts and to ensure that credentials known
46   * to be invalid are not retried. HttpClient will simply store the set of
47   * credentials returned by the custom credentials provider in the
48   * {@link org.apache.commons.httpclient.HttpState http state} object and will
49   * attempt to use these credentials for all subsequent requests with the given
50   * authentication scope.
51   * </p>
52   * <p>
53   * Classes implementing this interface must synchronize access to shared data as
54   * methods of this interfrace may be executed from multiple threads
55   * </p>
56   * 
57   * 
58   * @author Ortwin Glueck
59   * @author <a href="mailto:oleg@ural.ru">Oleg Kalnichevski</a>
60   * 
61   * @since 3.0
62   */
63  public interface CredentialsProvider {
64  
65      /**
66       * Sets the credentials provider parameter.
67       * <p>
68       * This parameter expects a value of type {@link CredentialsProvider}.
69       * </p>
70       */ 
71      public static final String PROVIDER = "http.authentication.credential-provider";
72      
73      /**
74       * Requests additional {@link Credentials authentication credentials}.
75       * 
76       * @param scheme the {@link AuthScheme authentication scheme}
77       * @param host the authentication host
78       * @param port the port of the authentication host
79       * @param proxy <tt>true</tt> if authenticating with a proxy,
80       *              <tt>false</tt> otherwise
81       */ 
82      public Credentials getCredentials(
83          final AuthScheme scheme, 
84          final String host, 
85          int port, 
86          boolean proxy) throws CredentialsNotAvailableException; 
87  
88  }