Calculator3


1   
2   package Jt.examples.patterns;
3   
4   import Jt.*;
5   import java.io.*;
6   import java.util.*;
7   import Jt.xml.*;
8   import java.beans.*;
9   
10  /**
11   * Calculator implementation based on Command, Memento, Strategy and Factory Method.
12   * Creating a subclass of JtCommand and implementing the processMessage
13   * method is basically all that is needed. Command requests are logged via
14   * the inherited logMessage() method. 
15   */
16  
17  public class Calculator3 extends JtCommand {
18  
19    transient Object   state = null;        // Object state
20    private int total = 0;                // Calculator Total
21    private JtMemento memento = null;     // Contains the state of the object
22                                          // needed to implement the undo operation
23   
24  
25    public Calculator3 () {
26    }
27  
28    public void setTotal (int total) {
29      this.total = total;
30    }
31  
32    public int getTotal () {
33      return (total);
34    }
35  
36    // Save calculator state
37  
38    private void saveState () {
39  
40      JtMessage msg = new JtMessage ("JtENCODE_OBJECT");
41      JtObject tmp = new JtObject();
42      Object   aux;
43  
44      msg.setMsgContent (this);
45      aux = tmp.processMessage  (msg);
46      
47      if (aux == null) {
48        handleWarning ("saveSate: Unable to save the current state"); 
49        return;
50      }
51  
52      // Use an instance of JtMemento to store the state
53  
54      if (memento == null)
55        memento = new JtMemento ();
56  
57      memento.setState (aux);
58  
59      handleTrace ("saveState: saving state ...\n" + aux);
60  
61    }
62  
63  
64    private void restoreState () {
65  
66      JtMessage msg = new JtMessage ("JtDECODE_OBJECT");
67      Calculator3 tmp;
68      JtObject copier = new JtObject ();
69  
70  
71      if (memento == null) {
72        handleWarning ("Warning: nothing to undo ....");
73        return;
74      }
75  
76      state = memento.getState ();
77      memento = null;
78   
79      if (state == null) {
80        handleWarning ("Warning: nothing to undo ....");
81        return;
82      }
83  
84      handleTrace ("restoreState (state) ...\n" + state);
85  
86      msg.setMsgContent (state);
87      //tmp = (Calculator1) xmlHelper.processMessage (msg);
88      tmp = (Calculator3) copier.processMessage (msg);
89  
90      msg = new JtMessage ("JtENCODE_OBJECT");
91      msg.setMsgContent (tmp);
92  
93      //System.out.println ("...\n" + copier.processMessage (msg));
94      //System.out.println ("src...\n" + tmp.getMessageLog ());
95  
96              
97      msg = new JtMessage ("JtCOPY_OBJECT");
98  
99      if (tmp == null) {
100       handleTrace ("restoreState failed: unable to convert object from XML"); 
101       return;
102     }
103     
104     msg.setMsgContent (tmp);
105     msg.setMsgData (this);
106     sendMessage (copier, msg);
107 
108     msg = new JtMessage ("JtENCODE_OBJECT");
109     msg.setMsgContent (this);
110 
111 
112   }
113 
114 
115 
116   /**
117     * Process object messages (Command requests).
118     * <ul>
119     * <li>ADD - Add a number (msgContent) to the total
120     * <li>MULTIPLY - Multiply a number (msgContent)
121     * </ul>
122     */
123 
124   public Object   processMessage (Object   message) {
125 
126    String   msgid = null;
127    JtMessage msg = (JtMessage) message;
128    Object   content;
129    JtMessage tmp;
130    Integer   mres;
131 
132      if (msg == null)
133     return null;
134 
135      // Retrieve Message ID and content
136 
137      msgid = (String  ) msg.getMsgId ();
138 
139      if (msgid == null)
140     return null;
141 
142      content = msg.getMsgContent();
143 
144      // Add a number to the total
145 
146      if (msgid.equals ("ADD")) {
147 
148         // Saves the state of the object
149         saveState ();
150 
151         // Log the request (message). This method is inherited from JtCommand
152    
153         logMessage (msg);  
154 
155         total += ((Integer  ) content).intValue ();            
156 
157         return (new Integer   (total));
158      }
159 
160 
161      if (msgid.equals ("MULTIPLY")) {
162 
163 
164         // Saves the state of the object
165         saveState ();
166 
167         // Log the message   
168         logMessage (msg);
169 
170         // Put together the MULTIPLY message
171   
172         tmp = new JtMessage ("MULTIPLY");
173         tmp.setMsgContent (new Integer   (total));
174         tmp.setMsgData (content);
175 
176         // the multiplication object (child of this object) is used
177         // to process multiplications.
178 
179         mres = (Integer  ) sendMessage ("multiplication", tmp);      
180 
181         total = mres.intValue ();             
182 
183         return (new Integer   (total));
184      }
185 
186 
187      if (msgid.equals ("UNDO")) {
188 
189  
190         restoreState ();
191         
192         return (new Integer   (total));
193      }
194 
195      // JtRemove message (Remove Object)
196 
197      if (msgid.equals ("JtREMOVE")) {
198        return (null);
199      }
200 
201      handleError ("Calculator3.processMessage: invalid message id:" + msgid);
202      return (null);
203   }
204 
205 
206  
207   /**
208    * Calculator implementation (main)
209    */
210 
211   public static void main(String  [] args) {
212 
213     JtObject main = new JtFactory ();
214     JtMessage msg, msg1;
215     Object   total;
216     JtKeyboard keyboard;
217     String   input;    
218     int num = 0;
219     Calculator3 calculator;
220     Multiplication multiplication;
221 
222 
223     // Create calculator, keyboard and multiplication
224 
225     calculator = (Calculator3) main.createObject ("Jt.examples.patterns.Calculator3", "calculator");
226     keyboard = (JtKeyboard) main.createObject ("Jt.JtKeyboard", "keyboard");
227     multiplication = (Multiplication) calculator.createObject 
228                   ("Jt.examples.patterns.Multiplication", "multiplication");
229 
230     do {
231       System.out.println  ("Please  select a multiplication strategy ...");
232       System.out.println  ("1. Standard multiplication");
233       System.out.println  ("2. Repetitive addition");
234 
235       input = (String  ) main.sendMessage (keyboard, new JtMessage ("JtACTIVATE"));
236 
237       if (input == null)
238         continue;
239 
240       input = input.trim ();
241 
242       if (input.equals ("1")) {
243         main.setValue (multiplication, "concreteStrategy", new MultiplicationA ());
244         break;
245       } else  if (input.equals ("2")) {
246         main.setValue (multiplication, "concreteStrategy", new MultiplicationB ());
247         break;
248       }
249     } while (true);
250     
251     for (;;) {
252 
253       System.out.println  ("Please  select an operation ...");
254       System.out.println  ("1. Addition");
255       System.out.println  ("2. Multiplication");
256       System.out.println  ("3. Undo the last operation");
257       System.out.println  ("4. Exit");
258 
259 
260       input = (String  ) main.sendMessage (keyboard, new JtMessage ("JtACTIVATE"));
261       if (input == null)
262         continue;
263 
264       input = input.trim ();
265 
266       if (input.equals ("4"))
267         break;
268 
269       if ("3".equals (input)) {
270         msg =  new JtMessage ("UNDO");
271         main.sendMessage ("calculator", msg);
272         System.out.println 
273          (">>> Total:" + main.getValue ("calculator", "total") + " <<<");
274         continue;
275       }
276 
277       if (input.equals ("1")) {
278         msg =  new JtMessage ("ADD");
279       } else if (input.equals ("2")) {
280         msg =  new JtMessage ("MULTIPLY");
281       } else
282         continue;
283 
284       System.out.print ("Enter a number --> ");
285 
286 
287       // Read input (number) from the keyboard (JtACTIVATE message)
288 
289       input = (String  ) main.sendMessage (keyboard, new JtMessage ("JtACTIVATE"));
290 
291       if (input != null)
292         input = input.trim ();
293 
294       if (input.equals (""))
295         continue;
296 
297 
298       try {
299         num = Integer.parseInt (input);
300       } catch (Exception   e) {
301 
302         System.err.println (e);
303         continue;
304       }
305 
306 
307       // Add the number to the Total (ADD Message)
308       //msg =  new JtMessage ("ADD");
309       msg.setMsgContent (new Integer   (num));   
310       total = main.sendMessage ("calculator", msg);
311 
312       System.out.println (">>> Total:" + total + " <<<");
313 
314     }
315 
316     // Print the log (list of requests executed by the calculator)
317     // Use main to convert the log information (messageLog)
318     // into XML.
319 
320     msg = new JtMessage ("JtENCODE_OBJECT");
321     msg.setMsgContent (main.getValue ("calculator", "messageLog"));
322 
323     System.out.println ("Log:\n" + 
324       main.sendMessage (main, msg));
325 
326 
327     // Remove object
328 
329     main.removeObject ("calculator");        
330 
331   }
332 
333 }
334 
335 
336 
337
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