1 //----------------------------------------------------------------------
2 //
3 // PerfectJPattern: "Design patterns are good but components are better!"
4 // IParameterlessHandler.java Copyright (c) 2009 Giovanni Azua Garcia
5 // bravegag@hotmail.com
6 //
7 // This program is free software; you can redistribute it and/or
8 // modify it under the terms of the GNU General Public License
9 // as published by the Free Software Foundation; either version 3
10 // of the License, or (at your option) any later version.
11 //
12 // This program is distributed in the hope that it will be useful,
13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 // GNU General Public License for more details.
16 //
17 // You should have received a copy of the GNU General Public License
18 // along with this program; if not, see <http://www.gnu.org/licenses/>.
19 //
20 //----------------------------------------------------------------------
21 package org.perfectjpattern.core.api.behavioral.chainofresponsibility;
22
23 /**
24 * <b>Chain of Responsibility Design Pattern</b>: Avoid coupling the sender of
25 * a request to its receiver by giving more than one object a chance to handle
26 * the request. Chain the receiving objects and pass the request along the chain
27 * until an object handles it. (Gamma et al, Design Patterns)<br/>
28 * <br/>
29 *
30 * <b>Responsibility</b>: Abstract definition of the "Handler".
31 *
32 * <ul>
33 * <li>Defines an interface for handling requests.</li>
34 * <li>Implements the Successor link.</li>
35 * </ul>
36 *
37 * <br/>
38 * Example usage:
39 * <pre><code>
40 * //
41 * // Create chain elements
42 * //
43 * IParameterlessHandler myFirst = new ConcreteHandler();
44 * IParameterlessHandler mySecond = new ConcreteHandler();
45 * IParameterlessHandler myThird = new ConcreteHandler();
46 *
47 * //
48 * // Associate Handler elements
49 * //
50 * myFirst.setSuccessor(mySecond);
51 * mySecond.setSuccessor(myThird);
52 *
53 * //
54 * // Execute the first Handler that triggers the execution of the
55 * // complete chain.
56 * //
57 * myFirst.start();
58 * </code></pre>
59 *
60 * @author <a href="mailto:bravegag@hotmail.com">Giovanni Azua</a>
61 * @version $Revision: 1.0 $ $Date: Nov 6, 2007 6:14:22 PM $
62 */
63 public
64 interface IParameterlessHandler
65 extends IHandler<NullRequest>
66 {
67 //------------------------------------------------------------------------
68 // public
69 //------------------------------------------------------------------------
70 /**
71 * Triggers execution of the Chain if the target Handler is the first
72 * reference, otherwise implements the decision-making regarding forwarding
73 * the request to its successor <code>IHandler</code> instance.
74 */
75 public void
76 start();
77
78 //------------------------------------------------------------------------
79 /**
80 * Handle the given request. Implements the actual handling logic and must
81 * not contain any decision-making regarding e.g. forwarding the request.
82 */
83 public void
84 handle();
85 }