Container


1   /* 
2    * Copyright 2003-2004 The Apache Software Foundation
3    * Licensed  under the  Apache License,  Version 2.0  (the "License");
4    * you may not use  this file  except in  compliance with the License.
5    * You may obtain a copy of the License at 
6    * 
7    *   http://www.apache.org/licenses/LICENSE-2.0
8    * 
9    * Unless required by applicable law or agreed to in writing, software
10   * distributed  under the  License is distributed on an "AS IS" BASIS,
11   * WITHOUT  WARRANTIES OR CONDITIONS  OF ANY KIND, either  express  or
12   * implied.
13   * 
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.avalon.fortress;
19  
20  import org.apache.avalon.framework.service.ServiceException;
21  
22  /**
23   * The Container is an interface used to mark the Containers in your system.
24   *
25   * <p>It is used to functionally identify Containers. It's primary use is to
26   * assist Container developers to obtain the desired object from the Context.
27   * Most applications will not, or barely, refer to implementations of this
28   * class; rather they will interact wit a {@link ContainerManager ContainerManager}
29   * implementation. All communication from the ContainerManager to the Container is
30   * through the {@link Context Context} object.</p>
31   *
32   * <p>While plans exist to extend the Container interface to expose more of the
33   * Container's internals, we currently feel that we have insufficient use case
34   * information to determine the generic form of the container internals.</p>
35   *
36   * @author <a HREF="mailto:dev@avalon.apache.org">The Avalon Team</a>
37   * @version CVS $Revision: 1.10 $ $Date: 2004/02/28 15:16:24 $
38   * @see ContainerConstants for the contract surrounding the Container context
39   * @see <a HREF="http://avalon.apache.org/framework/guide-cop-in-avalon.html">COP In Avalon</a>
40   */
41  public interface Container
42  {
43      /**
44       * Work interface identifier.
45       *
46       * @since 1.1-dev
47       */
48      String   ROLE = Container.class.getName();
49  
50      /**
51       * This is the method that the ContainerComponentManager and Selector use
52       * to gain access to the ComponentHandlers and ComponentSelectors.  The
53       * actual access of the ComponentHandler is delegated to the Container.
54       *
55       * @param  key  The role we intend to access a Component for.
56       * @param  hint  The hint that we use as a qualifier
57       *         (note: if null, the default implementation is returned).
58       *
59       * @return Object  a reference to the ComponentHandler or
60       *                 ComponentSelector for the role/hint combo.
61       *
62       * @throws ServiceException if the container cannot get the component
63       */
64      Object   get( String   key, Object   hint ) throws ServiceException;
65  
66      /**
67       * This is the method that the ContainerComponentManager and Selector use
68       * to gain access to the ComponentHandlers and ComponentSelectors.  The
69       * actual access of the ComponentHandler is delegated to the Container.
70       *
71       * @param  key  The role we intend to access a Component for.
72       * @param  hint  The hint that we use as a qualifier
73       *         (note: if null, the default implementation is returned).
74       *
75       * @return true  if a reference to the role exists.
76       */
77      boolean has( String   key, Object   hint );
78  }
79  
80
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