TriggerDef


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30  
31  
32  package org.hsqldb;
33  
34  import org.hsqldb.HsqlNameManager.HsqlName;
35  import org.hsqldb.lib.HsqlDeque;
36  import org.hsqldb.lib.StringConverter;
37  import org.hsqldb.lib.StringUtil;
38  
39  // peterhudson@users 20020130 - patch 478657 by peterhudson - triggers support
40  // fredt@users 20020130 - patch 1.7.0 by fredt
41  // added new class as jdk 1.1 does not allow use of LinkedList
42  // fredt@users 20030727 - signature and other alterations
43  // fredt@users 20040430 - changes by mattshaw@users to allow termination of the
44  // trigger thread -
45  
46  /**
47   *  Represents an HSQLDB Trigger definition. <p>
48   *
49   *  Provides services regarding HSLDB Trigger execution and metadata. <p>
50   *
51   *  Development of the trigger implementation sponsored by Logicscope
52   *  Realisations Ltd
53   *
54   * @author Peter Hudson - Logicscope Realisations Ltd
55   * @version  1.7.0 (1.0.0.3)
56   *      Revision History: 1.0.0.1 First release in hsqldb 1.61
57   *      1.0.0.2 'nowait' support to prevent deadlock 1.0.0.3 multiple row
58   *      queue for each trigger
59   */
60  class TriggerDef extends Thread   {
61  
62      /**
63       *  member variables
64       */
65      static final int NUM_TRIGGER_OPS = 3;                          // {ins,del,upd}
66      static final int NUM_TRIGS       = NUM_TRIGGER_OPS * 2 * 2;    // {b, a},{fer, fes}
67  
68      // other variables
69      HsqlName name;
70      String     when;
71      String     operation;
72      boolean  forEachRow;
73      boolean  nowait;                                               // block or overwrite if queue full
74      int      maxRowsQueued;                                        // max size of queue of pending triggers
75  
76      /**
77       *  Retrieves the queue size assigned to trigger definitions when no
78       *  queue size is explicitly declared. <p>
79       *
80       * @return the queue size assigned to trigger definitions when no
81       *      queue size is explicitly declared
82       */
83      public static int getDefaultQueueSize() {
84          return defaultQueueSize;
85      }
86  
87      protected static int defaultQueueSize = 1024;
88      Table                table;
89      Trigger              trigger;
90      String                 triggerClassName;
91      int                  vectorIndex;               // index into HsqlArrayList[]
92  
93      //protected boolean busy;               // firing trigger in progress
94      protected HsqlDeque        pendingQueue;        // row triggers pending
95      protected int              rowsQueued;          // rows in pendingQueue
96      protected boolean          valid     = true;    // parsing valid
97      protected volatile boolean keepGoing = true;
98  
99      /**
100      *  Constructs a new TriggerDef object to represent an HSQLDB trigger
101      *  declared in an SQL CREATE TRIGGER statement.
102      *
103      *  Changes in 1.7.2 allow the queue size to be specified as 0. A zero
104      *  queue size causes the Trigger.fire() code to run in the main thread of
105      *  execution (fully inside the enclosing transaction). Otherwise, the code
106      *  is run in the Trigger's own thread.
107      *  (fredt@users)
108      *
109      * @param  name The trigger object's HsqlName
110      * @param  when the String representation of whether the trigger fires
111      *      before or after the triggering event
112      * @param  operation the String representation of the triggering operation;
113      *      currently insert, update, or delete
114      * @param  forEach indicates whether the trigger is fired for each row
115      *      (true) or statement (false)
116      * @param  table the Table object upon which the indicated operation
117      *      fires the trigger
118      * @param  triggerClassName the fully qualified named of the class implementing
119      *      the org.hsqldb.Trigger (trigger body) interface
120      * @param  noWait do not wait for available space on the pending queue; if
121      *      the pending queue does not have fewer than nQueueSize queued items,
122      *      then overwrite the current tail instead
123      * @param  queueSize the length to which the pending queue may grow before
124      *      further additions are either blocked or overwrite the tail entry,
125      *      as determined by noWait
126      * @throws HsqlException - Invalid input parameter
127      */
128     public TriggerDef(HsqlNameManager.HsqlName name, String   when,
129                       String   operation, boolean forEach, Table table,
130                       String   triggerClassName, boolean noWait, int queueSize,
131                       ClassLoader   loader) throws HsqlException {
132 
133         this.name             = name;
134         this.when             = when;
135         this.operation        = operation;
136         this.forEachRow       = forEach;
137         this.nowait           = noWait;
138         this.maxRowsQueued    = queueSize;
139         this.table            = table;
140         vectorIndex           = SqlToIndex();
141         this.triggerClassName = triggerClassName;
142         rowsQueued            = 0;
143         pendingQueue          = new HsqlDeque();
144 
145         if (vectorIndex < 0) {
146             throw Trace.error(Trace.UNEXPECTED_TOKEN,
147                               Trace.CREATE_TRIGGER_COMMAND_1);
148         }
149 
150         Class   cl;
151 
152         try {
153             cl = loader == null ? Class.forName(triggerClassName)
154                                 : loader.loadClass(triggerClassName);
155         } catch (ClassNotFoundException   e) {
156             valid = false;
157             cl    = DefaultTrigger.class;
158         }
159 
160         try {
161 
162             // dynamically instantiate it
163             trigger = (Trigger) cl.newInstance();
164         } catch (Exception   e) {
165             valid = false;
166             cl    = DefaultTrigger.class;
167         }
168     }
169 
170     /**
171      *  Retrieves the SQL character sequence required to (re)create the
172      *  trigger, as a StringBuffer
173      *
174      * @return the SQL character sequence required to (re)create the
175      *  trigger
176      */
177     public StringBuffer   getDDL() {
178 
179         StringBuffer   a = new StringBuffer  (256);
180 
181         a.append(Token.T_CREATE).append(' ');
182         a.append(Token.T_TRIGGER).append(' ');
183         a.append(name.statementName).append(' ');
184         a.append(when).append(' ');
185         a.append(operation).append(' ');
186         a.append(Token.T_ON).append(' ');
187         a.append(table.getName().statementName).append(' ');
188 
189         if (forEachRow) {
190             a.append(Token.T_FOR).append(' ');
191             a.append(Token.T_EACH).append(' ');
192             a.append(Token.T_ROW).append(' ');
193         }
194 
195         if (nowait) {
196             a.append(Token.T_NOWAIT).append(' ');
197         }
198 
199         if (maxRowsQueued != getDefaultQueueSize()) {
200             a.append(Token.T_QUEUE).append(' ');
201             a.append(maxRowsQueued).append(' ');
202         }
203 
204         a.append(Token.T_CALL).append(' ');
205         a.append(StringConverter.toQuotedString(triggerClassName, '"',
206                 false));
207 
208         return a;
209     }
210 
211     /**
212      *  SqlToIndex method declaration <P>
213      *
214      *  Given the SQL creating the trigger, say what the index to the
215      *  HsqlArrayList[] is
216      *
217      * @return  index to the HsqlArrayList[]
218      */
219     public int SqlToIndex() {
220 
221         int indx;
222 
223         if (operation.equals(Token.T_INSERT)) {
224             indx = Trigger.INSERT_AFTER;
225         } else if (operation.equals(Token.T_DELETE)) {
226             indx = Trigger.DELETE_AFTER;
227         } else if (operation.equals(Token.T_UPDATE)) {
228             indx = Trigger.UPDATE_AFTER;
229         } else {
230             return -1;
231         }
232 
233         if (when.equals(Token.T_BEFORE)) {
234             indx += NUM_TRIGGER_OPS;    // number of operations
235         } else if (!when.equals(Token.T_AFTER)) {
236             return -1;
237         }
238 
239         if (forEachRow) {
240             indx += 2 * NUM_TRIGGER_OPS;
241         }
242 
243         return indx;
244     }
245 
246     public static int indexToRight(int idx) {
247 
248         switch (idx) {
249 
250             case Trigger.DELETE_AFTER :
251             case Trigger.DELETE_AFTER_ROW :
252             case Trigger.DELETE_BEFORE :
253             case Trigger.DELETE_BEFORE_ROW :
254                 return UserManager.DELETE;
255 
256             case Trigger.INSERT_AFTER :
257             case Trigger.INSERT_AFTER_ROW :
258             case Trigger.INSERT_BEFORE :
259             case Trigger.INSERT_BEFORE_ROW :
260                 return UserManager.INSERT;
261 
262             case Trigger.UPDATE_AFTER :
263             case Trigger.UPDATE_AFTER_ROW :
264             case Trigger.UPDATE_BEFORE :
265             case Trigger.UPDATE_BEFORE_ROW :
266                 return UserManager.UPDATE;
267 
268             default :
269                 return 0;
270         }
271     }
272 
273     /**
274      *  run method declaration <P>
275      *
276      *  the trigger JSP is run in its own thread here. Its job is simply to
277      *  wait until it is told by the main thread that it should fire the
278      *  trigger.
279      */
280     public void run() {
281 
282         while (keepGoing) {
283             TriggerData triggerData = popPair();
284 
285             if (triggerData != null) {
286                 if (triggerData.username != null) {
287                     trigger.fire(this.vectorIndex, name.name,
288                                  table.getName().name, triggerData.oldRow,
289                                  triggerData.newRow);
290                 }
291             }
292         }
293     }
294 
295     /**
296      * start the thread if this is threaded
297      */
298     public synchronized void start() {
299 
300         if (maxRowsQueued != 0) {
301             super.start();
302         }
303     }
304 
305     /**
306      * signal the thread to stop
307      */
308     public synchronized void terminate() {
309 
310         keepGoing = false;
311 
312         notify();
313     }
314 
315     /**
316      *  pop2 method declaration <P>
317      *
318      *  The consumer (trigger) thread waits for an event to be queued <P>
319      *
320      *  <B>Note: </B> This push/pop pairing assumes a single producer thread
321      *  and a single consumer thread _only_.
322      *
323      * @return  Description of the Return Value
324      */
325     synchronized TriggerData popPair() {
326 
327         if (rowsQueued == 0) {
328             try {
329                 wait();    // this releases the lock monitor
330             } catch (InterruptedException   e) {
331 
332                 /* ignore and resume */
333             }
334         }
335 
336         rowsQueued--;
337 
338         notify();    // notify push's wait
339 
340         if (pendingQueue.size() == 0) {
341             return null;
342         } else {
343             return (TriggerData) pendingQueue.removeFirst();
344         }
345     }
346 
347     /**
348      *  The main thread tells the trigger thread to fire by this call.
349      *  If this Trigger is not threaded then the fire method is caled
350      *  immediately and executed by the main thread. Otherwise, the row
351      *  data objects are added to the queue to be used by the Trigger thread.
352      *
353      * @param  row1
354      * @param  row2
355      */
356     synchronized void pushPair(Session session, Object  [] row1,
357                                Object  [] row2) {
358 
359         if (maxRowsQueued == 0) {
360             trigger.fire(vectorIndex, name.name, table.getName().name, row1,
361                          row2);
362 
363             return;
364         }
365 
366         if (rowsQueued >= maxRowsQueued) {
367             if (nowait) {
368                 pendingQueue.removeLast();    // overwrite last
369             } else {
370                 try {
371                     wait();
372                 } catch (InterruptedException   e) {
373 
374                     /* ignore and resume */
375                 }
376 
377                 rowsQueued++;
378             }
379         } else {
380             rowsQueued++;
381         }
382 
383         pendingQueue.add(new TriggerData(session, row1, row2));
384         notify();    // notify pop's wait
385     }
386 
387     /**
388      *  Method declaration
389      *
390      * @return
391      */
392     public boolean isBusy() {
393         return rowsQueued != 0;
394     }
395 
396     /**
397      *  Method declaration
398      *
399      * @return
400      */
401     public boolean isValid() {
402         return valid;
403     }
404 
405     /**
406      * Class to store the data used to fire a trigger. The username attribute
407      * is not used but it allows developers to change the signature of the
408      * fire method of the Trigger class and pass the user name to the Trigger.
409      */
410     class TriggerData {
411 
412         public Object  [] oldRow;
413         public Object  [] newRow;
414         public String     username;
415 
416         public TriggerData(Session session, Object  [] oldRow,
417                            Object  [] newRow) {
418 
419             this.oldRow   = oldRow;
420             this.newRow   = newRow;
421             this.username = session.getUsername();
422         }
423     }
424 
425     static class DefaultTrigger implements org.hsqldb.Trigger {
426 
427         public void fire(int i, String   name, String   table, Object  [] row1,
428                          Object  [] row2) {
429             throw new RuntimeException  ("Missing Trigger class!");
430         }
431     }
432 }
433
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