ComponentAdapter


1   /*****************************************************************************
2    * Copyright (C) PicoContainer Organization. All rights reserved.            *
3    * ------------------------------------------------------------------------- *
4    * The software in this package is published under the terms of the BSD      *
5    * style license a copy of which has been included with this distribution in *
6    * the LICENSE.txt file.                                                     *
7    *****************************************************************************/
8   package org.picocontainer;
9   
10  /**
11   * A component adapter is responsible for providing a specific component instance. An instance of an implementation of
12   * this interface is used inside a {@link PicoContainer} for every registered component or instance.  Each
13   * <code>ComponentAdapter</code> instance has to have a key which is unique within that container. The key itself is
14   * either a class type (normally an interface) or an identifier.
15   *
16   * @author Jon Tirs&eacute;n
17   * @author Paul Hammant
18   * @author Aslak Helles&oslash;y
19   * @version $Revision: 1801 $
20   * @see MutablePicoContainer an extension of the PicoContainer interface which allows you to modify the contents of the
21   *      container.
22   * @since 1.0
23   */
24  public interface ComponentAdapter {
25      /**
26       * Retrieve the key associated with the component.
27       * 
28       * @return the component's key. Should either be a class type (normally an interface) or an identifier that is
29       *         unique (within the scope of the current PicoContainer).
30       */
31      Object   getComponentKey();
32  
33      /**
34       * Retrieve the class of the component.
35       * 
36       * @return the component's implementation class. Should normally be a concrete class (ie, a class that can be
37       *         instantiated).
38       */
39      Class   getComponentImplementation();
40  
41      /**
42       * Retrieve the component instance. This method will usually create a new instance each time it is called, but that
43       * is not required. For example, {@link org.picocontainer.defaults.CachingComponentAdapter} will always return the
44       * same instance.
45       * 
46       * @param container the {@link PicoContainer}, that is used to resolve any possible dependencies of the instance.
47       * @return the component instance.
48       * @throws PicoInitializationException if the component could not be instantiated.
49       * @throws PicoIntrospectionException  if the component has dependencies which could not be resolved, or
50       *                                     instantiation of the component lead to an ambigous situation within the
51       *                                     container.
52       */
53      Object   getComponentInstance(PicoContainer container) throws PicoInitializationException, PicoIntrospectionException;
54  
55      /**
56       * Verify that all dependencies for this adapter can be satisifed. Normally, the adapter should verify this by
57       * checking that the associated PicoContainer contains all the needed dependnecies.
58       *
59       * @param container the {@link PicoContainer}, that is used to resolve any possible dependencies of the instance.
60       * @throws PicoIntrospectionException if one or more dependencies cannot be resolved.
61       */
62      void verify(PicoContainer container) throws PicoIntrospectionException;
63  
64      /**
65       * Accepts a visitor for this ComponentAdapter. The method is normally called by visiting a {@link PicoContainer}, that 
66       * cascades the visitor also down to all its ComponentAdapter instances.
67       * 
68       * @param visitor the visitor.
69       * @since 1.1
70       */
71      void accept(PicoVisitor visitor);
72  }
73
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