JtStrategy


1   
2   
3   package Jt;
4   import java.util.*;
5   import java.lang.reflect.*;
6   import java.beans.*;
7   import java.io.*;
8   
9   /**
10   * Jt implementation of the Strategy pattern.
11   */
12  
13  public class JtStrategy extends JtObject {
14  
15  
16    private Object   concreteStrategy = null; // Concrete Strategy object
17  
18  
19    public JtStrategy () {
20    }
21  
22  
23  
24  /**
25    * Specifies the reference to the concrete strategy.
26    */
27  
28  
29    public void setConcreteStrategy (Object   concreteStrategy) {
30       this.concreteStrategy = concreteStrategy;
31    }
32  
33  
34  /**
35    * Returns the reference to the concrete strategy.
36    */
37  
38    public Object   getConcreteStrategy () {
39       return (concreteStrategy);
40    }
41  
42  
43  
44  
45  
46  
47    /**
48      * Process object messages.
49      * <ul>
50      * <li>JtREMOVE - Performs any housekeeping that may be needed before the object
51      * is removed.
52      * </ul>
53      */
54  
55    public Object   processMessage (Object   event) {
56  
57     String   msgid = null;
58     JtMessage e = (JtMessage) event;
59     Object   content;
60     Object   data;
61  
62  
63       if (e == null)
64      return null;
65  
66       msgid = (String  ) e.getMsgId ();
67  
68       if (msgid == null)
69      return null;
70  
71       content = e.getMsgContent();
72       //data = e.getMsgData ();
73  
74  
75       if (msgid.equals ("JtREMOVE")) {
76         return (null);     
77       }
78  
79       // Let the concrete strategy object handle the message
80  
81       if (concreteStrategy == null) {
82         handleError ("processMessage: concreteStrategy attribute must be set");
83         return (null);
84       }
85  
86       return (((JtObject) concreteStrategy).processMessage (event));
87  
88  
89    }
90  
91   
92    /**
93     * Unit tests the messages processed by JtStrategy.
94     */
95  
96    public static void main(String  [] args) {
97  
98      JtFactory factory = new JtFactory ();
99      JtStrategy strategy;
100     JtObject concreteStrategy;
101 
102     // Create an instance of JtStrategy
103 
104     strategy = (JtStrategy) factory.createObject ("Jt.JtStrategy", "strategy");
105 
106     // Specify the concrete strategy to be executed
107 
108     concreteStrategy = (JtObject) factory.createObject ("Jt.JtEcho", "concreteStrategy");
109     factory.setValue (strategy, "concreteStrategy", concreteStrategy);
110 
111     
112     factory.sendMessage (strategy, new JtMessage ("JtEXECUTE_STRATEGY"));
113 
114     factory.removeObject ("strategy");
115 
116 
117   }
118 
119 }
120 
121 
122
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