AbstractComponentAdapter


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    * Original code by                                                          *
9    *****************************************************************************/
10  package org.picocontainer.defaults;
11  
12  import org.picocontainer.ComponentAdapter;
13  import org.picocontainer.PicoVisitor;
14  
15  import java.io.Serializable  ;
16  
17  /**
18   * Base class for a ComponentAdapter with general functionality.
19   * This implementation provides basic checks for a healthy implementation of a ComponentAdapter.
20   * It does not allow to use <code>null</code> for the component key or the implementation, 
21   * ensures that the implementation is a concrete class and that the key is assignable from the 
22   * implementation if the key represents a type.   
23   *  
24   * @author Paul Hammant
25   * @author Aslak Helles&oslash;y
26   * @author Jon Tirs&eacute;n
27   * @version $Revision: 1570 $
28   * @since 1.0
29   */
30  public abstract class AbstractComponentAdapter implements ComponentAdapter, Serializable   {
31      private Object   componentKey;
32      private Class   componentImplementation;
33  
34      /**
35       * Constructs a new ComponentAdapter for the given key and implementation. 
36       * @param componentKey the search key for this implementation
37       * @param componentImplementation the concrete implementation
38       * @throws AssignabilityRegistrationException if the key is a type and the implementation cannot be assigned to.
39       */
40      protected AbstractComponentAdapter(Object   componentKey, Class   componentImplementation) throws AssignabilityRegistrationException {
41          if (componentImplementation == null) {
42              throw new NullPointerException  ("componentImplementation");
43          }
44          this.componentKey = componentKey;
45          this.componentImplementation = componentImplementation;
46          checkTypeCompatibility();
47      }
48  
49      /**
50       * {@inheritDoc}
51       * @see org.picocontainer.ComponentAdapter#getComponentKey()
52       */
53      public Object   getComponentKey() {
54          if (componentKey == null) {
55              throw new NullPointerException  ("componentKey");
56          }
57          return componentKey;
58      }
59  
60      /**
61       * {@inheritDoc}
62       * @see org.picocontainer.ComponentAdapter#getComponentImplementation()
63       */
64      public Class   getComponentImplementation() {
65          return componentImplementation;
66      }
67  
68      protected void checkTypeCompatibility() throws AssignabilityRegistrationException {
69          if (componentKey instanceof Class  ) {
70              Class   componentType = (Class  ) componentKey;
71              if (!componentType.isAssignableFrom(componentImplementation)) {
72                  throw new AssignabilityRegistrationException(componentType, componentImplementation);
73              }
74          }
75      }
76  
77      /**
78       * @return Returns the ComponentAdapter's class name and the component's key.
79       * @see java.lang.Object#toString()
80       */
81      public String   toString() {
82          return getClass().getName() + "[" + getComponentKey() + "]";
83      }
84  
85      public void accept(PicoVisitor visitor) {
86          visitor.visitComponentAdapter(this);
87      }
88  }
89
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