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1   /*
2    * Copyright [2006] [University Corporation for Advanced Internet Development, Inc.]
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    * http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package org.opensaml.saml2.metadata.provider;
18  
19  import java.util.List;
20  
21  /**
22   * A metadata provider that provides event notification to observers. This may be used, for example, to signal an update
23   * of an internal cache of metadata allowing other subsystems to perform some action based on that.
24   * 
25   */
26  public interface ObservableMetadataProvider extends MetadataProvider {
27  
28      /**
29       * Gets the list of observers for the provider. New observers may be added to the list or old ones removed.
30       * 
31       * @return the list of observers
32       */
33      public List<Observer> getObservers();
34  
35      /**
36       * An observer of metadata provider changes.
37       * 
38       * <strong>NOTE:</strong> The metadata provider that has changed is passed in to the
39       * {@link #onEvent(MetadataProvider)} method. Observers should <strong>NOT</strong> keep a reference to this
40       * provider as this may prevent proper garbage collection.
41       */
42      public interface Observer {
43  
44          /**
45           * Called when a provider signals an event has occured.
46           * 
47           * @param provider the provider being observed
48           */
49          public void onEvent(MetadataProvider provider);
50      }
51  }