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1   /* This file is part of COPAL (COntext Provisioning for All).
2    *
3    * COPAL is a part of SM4All (Smart hoMes for All) project.
4    *
5    * COPAL is free software: you can redistribute it and/or modify
6    * it under the terms of the GNU Lesser General Public License as published by
7    * the Free Software Foundation, either version 3 of the License, or
8    * (at your option) any later version.
9    *
10   * COPAL is distributed in the hope that it will be useful,
11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13   * GNU Lesser General Public License for more details.
14   *
15   * You should have received a copy of the GNU Lesser General Public License
16   * along with COPAL. If not, see <http://www.gnu.org/licenses/>.
17   */
18  package at.ac.tuwien.infosys.sm4all.copal.api.util;
19  
20  /**
21   * The interface which represents a {@link Registry} {@link Observable}.
22   * 
23   * @param <T> the type of values maintained by the {@link Registry}.
24   * @author sanjin
25   */
26  public interface RegistryObservable<T>
27          extends
28          Observable<RegistryObservable.RegistrationState, T, RegistryObservable.RegistryObserver<T>> {
29  
30      /**
31       * The states of a value that is registered in {@link Registry}.
32       * 
33       * @author sanjin
34       */
35      public enum RegistrationState {
36  
37          /**
38           * The value is registered.
39           */
40          Registered,
41          /**
42           * The value is unregistered.
43           */
44          Unregistered
45      }
46  
47      /**
48       * Interface to be implemented by {@link Observer}s which are interested on
49       * notifications of {@link Registry} changes.
50       * 
51       * @param <T> the type of values maintained by the {@link Registry}.
52       * @author sanjin
53       */
54      interface RegistryObserver<T> extends Observer<RegistrationState, T> {
55  
56          /**
57           * Called when specified objects changes its {@link RegistrationState}
58           * with a {@link BaseRegistry}.
59           * 
60           * @param state the {@link RegistrationState}.
61           * @param object the changed object.
62           */
63          @Override
64          void update(RegistrationState state, T object);
65      }
66  }