SingletonTemplateMixin


1   package org.objectweb.fractal.julia.factory;
2   
3   import org.objectweb.fractal.api.Component;
4   import org.objectweb.fractal.api.factory.InstantiationException;
5   
6   /**
7    * Provides a singleton behavior to a {@link Template}.
8    * <b>A singleton composite template must only contain other singleton
9    * templates, otherwise the "singleton" semantics will not be ensured.</b>
10   * <br>
11   * <br>
12   * <b>Requirements</b>
13   * <ul>
14   * <li>none.</li>
15   * </ul>
16   */
17  
18  public abstract class SingletonTemplateMixin implements Template {
19  
20    // -------------------------------------------------------------------------
21    // Private constructor
22    // -------------------------------------------------------------------------
23  
24    private SingletonTemplateMixin () {
25    }
26  
27    // -------------------------------------------------------------------------
28    // Fields and methods added and overriden by the mixin class
29    // -------------------------------------------------------------------------
30  
31    /**
32     * The singleton instance created by this template.
33     */
34  
35    public Component fcInstance;
36  
37    /**
38     * Calls the overriden method only if the {@link #fcInstance} field is
39     * <tt>null</tt>.
40     * 
41     * @return the instantiated component.
42     * @throws InstantiationException if the component controller cannot be
43     *      instantiated.
44     */
45  
46    public Component newFcControllerInstance () throws InstantiationException   {
47      if (fcInstance == null) {
48        fcInstance = _super_newFcControllerInstance();
49      }
50      return fcInstance;
51    }
52  
53    // -------------------------------------------------------------------------
54    // Fields and methods required by the mixin class in the base class
55    // -------------------------------------------------------------------------
56  
57    /**
58     * The {@link Template#newFcControllerInstance newFcControllerInstance}
59     * overriden by this mixin.
60     * 
61     * @return the instantiated component.
62     * @throws InstantiationException if the component controller cannot be
63     *      instantiated.
64     */
65  
66    public abstract Component _super_newFcControllerInstance () 
67      throws InstantiationException  ;
68  }
69
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags