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Java > Open Source Codes > demo > bank > concurrency > AccountImpl


1 package demo.bank.concurrency;
2
3
4
5 /**
6
7  * Simple Transaction Service example, code taken and adapted
8
9  * from http://www.wiley.com/compbooks/vogel/ejb/code.html
10
11  */
12
13
14
15 import org.omg.CORBA.*;
16
17 import org.omg.CosTransactions.*;
18
19 import org.omg.CosConcurrencyControl.*;
20
21 import org.omg.CosConcurrencyControl.*;
22
23
24
25 public class AccountImpl
26
27     extends AccountPOA
28
29 {
30
31     private float balance;
32
33     private float newBalance;
34
35     private TransactionalLockSet lock_set;
36
37     private String JavaDoc name;
38
39     private int id;
40
41     private Coordinator current_transaction = null;
42
43     private boolean prepared = false;
44
45
46
47     public AccountImpl( TransactionalLockSet lock_set, String JavaDoc name, float deposit, int id )
48
49     {
50
51     this.name = name;
52
53         this.lock_set = lock_set;
54
55         this.id = id;
56
57     balance = deposit;
58
59         newBalance = balance;
60
61     }
62
63
64
65     public synchronized float get_balance( Control control ){
66
67         try {
68
69             Coordinator coord = control.get_coordinator();
70
71             // If my transaction change account or nobody change account
72
73             if( lock_set.try_lock( coord, lock_mode.read ) ) {
74
75                 float r = newBalance;
76
77                 lock_set.unlock( coord, lock_mode.read );
78
79                 return r;
80
81             } else {
82
83                 // Anybody change account get_last valid data
84
85                 return balance;
86
87             }
88
89         } catch ( Exception JavaDoc e ) {
90
91             e.printStackTrace();
92
93             throw new org.omg.CORBA.INTERNAL JavaDoc();
94
95         }
96
97     }
98
99
100
101     public synchronized void debit( float amount, Control control )
102
103     throws InsufficientFunds
104
105     {
106
107     try
108
109     {
110
111             Coordinator coord = control.get_coordinator();
112
113
114
115         // lock account for write
116
117         while( ! lock_set.try_lock( coord, lock_mode.write ) ){
118
119                 try {
120
121                     wait();
122
123                 } catch ( Exception JavaDoc e ){
124
125                     e.printStackTrace();
126
127                 }
128
129             }
130
131
132
133         // check founds
134
135         if( amount > newBalance ) {
136
137         lock_set.unlock( coord, lock_mode.write );
138
139         System.out.println("Resource: " + name + " account unlocked");
140
141         throw new InsufficientFunds();
142
143         }
144
145         newBalance -= amount;
146
147             if( current_transaction == null ){
148
149                 current_transaction = coord;
150
151                 coord.register_resource( _this() );
152
153             };
154
155     } catch( Unavailable u ) {
156
157         System.err.println("Account " + name + "::debit: exception: " + u );
158
159     } catch( LockNotHeld h ) {
160
161         System.err.println("Account " + name + "::debit: exception: " + h );
162
163     } catch( Inactive i ) {
164
165         System.err.println("Account " + name + "::debit: exception: " + i );
166
167     } catch( SystemException se ) {
168
169         System.err.println("Account " + name + "::debit: exception: " + se );
170
171     };
172
173     }
174
175
176
177     public synchronized void credit( float amount, Control control )
178
179     {
180
181     try
182
183     {
184
185             Coordinator coord = control.get_coordinator();
186
187         // lock account for write
188
189         while( ! lock_set.try_lock( coord, lock_mode.write ) ){
190
191                 try {
192
193                     wait();
194
195                 } catch ( Exception JavaDoc e ){
196
197                     e.printStackTrace();
198
199                 }
200
201             }
202
203
204
205         newBalance += amount;
206
207             if( current_transaction == null ){
208
209                 current_transaction = coord;
210
211                 coord.register_resource( _this() );
212
213             };
214
215     }
216
217     catch( Unavailable u ) {
218
219         System.err.println("Account " + name + "::credit: exception: " + u );
220
221     }
222
223     catch( Inactive i ) {
224
225         System.err.println("Account " + name + "::credit: exception: " + i );
226
227     }
228
229     catch( SystemException se ) {
230
231         System.err.println("Account " + name + "::credit: exception: " + se );
232
233     }
234
235     }
236
237
238
239     public TransactionalLockSet get_lock_set(){
240
241         return lock_set;
242
243     };
244
245
246
247     public java.lang.String JavaDoc owner(){
248
249         return name;
250
251     };
252
253
254
255     public int account_code(){
256
257         return id;
258
259     };
260
261
262
263     // implement methods of the Resource interface
264
265
266
267     public synchronized Vote prepare()
268
269     {
270
271     if( balance == newBalance )
272
273         return Vote.VoteReadOnly;
274
275     return Vote.VoteCommit;
276
277     }
278
279
280
281     public synchronized void rollback() {
282
283         newBalance = balance;
284
285         current_transaction = null;
286
287         notifyAll();
288
289     }
290
291
292
293     public synchronized void commit() {
294
295     balance = newBalance;
296
297         current_transaction = null;
298
299         notifyAll();
300
301     }
302
303
304
305     public synchronized void commit_one_phase()
306
307     {
308
309     if(prepare() == Vote.VoteCommit) {
310
311         commit();
312
313     }
314
315     }
316
317
318
319     public synchronized void forget()
320
321     {
322
323         System.out.println("Resource " + name + " : forget()");
324
325     }
326
327 }
328
329
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