Source Code Cross Referenced for Function.java in  » Development » JoSQL » org » josql » expressions » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Development » JoSQL » org.josql.expressions 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         * Copyright 2004-2007 Gary Bentley 
003:         * 
004:         * Licensed under the Apache License, Version 2.0 (the "License"); you may 
005:         * not use this file except in compliance with the License. 
006:         * You may obtain a copy of the License at 
007:         *    http://www.apache.org/licenses/LICENSE-2.0 
008:         *
009:         * Unless required by applicable law or agreed to in writing, software 
010:         * distributed under the License is distributed on an "AS IS" BASIS, 
011:         * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
012:         * See the License for the specific language governing permissions and 
013:         * limitations under the License.
014:         */
015:        package org.josql.expressions;
016:
017:        import java.util.List;
018:        import java.util.Arrays;
019:        import java.util.Map;
020:        import java.util.TreeMap;
021:
022:        import java.lang.reflect.Method;
023:        import java.lang.reflect.Modifier;
024:
025:        import com.gentlyweb.utils.Getter;
026:
027:        import org.josql.Query;
028:        import org.josql.QueryExecutionException;
029:        import org.josql.QueryParseException;
030:
031:        import org.josql.internal.Utilities;
032:
033:        import org.josql.functions.NotFixedResults;
034:
035:        /**
036:         * This class represents a Function that can be "called" in JoSQL.  
037:         */
038:        public class Function extends ValueExpression {
039:
040:            private String name = null;
041:            private List params = null;
042:            private Method function = null;
043:            private Object handler = null;
044:            private boolean fixedResult = true;
045:            private Object fixedValue = null;
046:            private String acc = null;
047:            private Getter get = null;
048:
049:            public Getter getGetter() {
050:
051:                return this .get;
052:
053:            }
054:
055:            public String getAccessor() {
056:
057:                return this .acc;
058:
059:            }
060:
061:            public void setAccessor(String acc) {
062:
063:                this .acc = acc;
064:
065:            }
066:
067:            /**
068:             * Get the expected return type from the function.  The exact class returned is 
069:             * dependent upon the function (Java method) that is being called.
070:             * 
071:             * @param q The Query object.
072:             * @return The class of the expected return type.
073:             */
074:            public Class getExpectedReturnType(Query q) {
075:
076:                if (this .get != null) {
077:
078:                    return this .get.getType();
079:
080:                }
081:
082:                return this .function.getReturnType();
083:
084:            }
085:
086:            /**
087:             * This is a complex method that will initialise the function.
088:             * Firstly all of the "arguments" to the function are inited and then
089:             * their expected return types gained from calling: {@link Function#getExpectedReturnType(Query)}.
090:             * Then the function handlers, user-defined and then built-in are searched until they
091:             * find a match for the function name, ensure that it's a public method and that all the
092:             * arguments match, widening the match where necessary.
093:             *
094:             * @param q The Query object.
095:             * @throws QueryParseException If something goes wrong whilst initing the arguments to the 
096:             *                             function or if the function cannot be found.
097:             */
098:            public void init(Query q) throws QueryParseException {
099:
100:                // Need to init the params (if present) first because the expected type may not be
101:                // present otherwise.
102:                if (this .params != null) {
103:
104:                    int s = this .params.size();
105:
106:                    for (int i = 0; i < s; i++) {
107:
108:                        Expression exp = (Expression) this .params.get(i);
109:
110:                        exp.init(q);
111:
112:                    }
113:
114:                }
115:
116:                // Try and find the relevant method, first in the user-defined function handler (if present)
117:                // or the built-in handlers.
118:                this .findMethod(q);
119:
120:                if (this .function == null) {
121:
122:                    Class[] ps = null;
123:
124:                    if (this .params != null) {
125:
126:                        int s = params.size();
127:
128:                        ps = new Class[s];
129:
130:                        for (int i = 0; i < s; i++) {
131:
132:                            // Need to get the expected return type.
133:                            Expression exp = (Expression) params.get(i);
134:
135:                            ps[i] = exp.getExpectedReturnType(q);
136:
137:                        }
138:
139:                    }
140:
141:                    // Can't find the function.
142:                    throw new QueryParseException(
143:                            "Unable to find function (method): \""
144:                                    + Utilities.formatSignature(this .name, ps)
145:                                    + "\" in any user-defined function handlers or the default function handler");
146:
147:                }
148:
149:                // Now see if we have an accessor for the function.
150:                if (this .acc != null) {
151:
152:                    this .initAccessor();
153:
154:                }
155:
156:                // A function has/can have a fixed result if all it's arguments
157:                // also have a fixed result, if there aren't any args then assume
158:                // it won't have a fixed result.
159:                if ((this .params != null)
160:                        && (!NotFixedResults.class
161:                                .isAssignableFrom(this .function
162:                                        .getDeclaringClass()))) {
163:
164:                    for (int i = 0; i < this .params.size(); i++) {
165:
166:                        Expression exp = (Expression) this .params.get(i);
167:
168:                        if (!exp.hasFixedResult(q)) {
169:
170:                            this .fixedResult = false;
171:                            break;
172:
173:                        }
174:
175:                    }
176:
177:                } else {
178:
179:                    this .fixedResult = false;
180:
181:                }
182:
183:            }
184:
185:            private void initAccessor() throws QueryParseException {
186:
187:                // We have an accessor, see what the functions return type is.
188:                Class retType = this .function.getReturnType();
189:
190:                // Ensure that the function DOES have a return type.
191:                if (Void.TYPE.isAssignableFrom(retType)) {
192:
193:                    // The return type is void, barf!
194:                    throw new QueryParseException(
195:                            "Function: "
196:                                    + this 
197:                                    + " maps to method: "
198:                                    + this .function
199:                                    + " however methods return type is \"void\" and an accessor: "
200:                                    + this .acc + " has been defined.");
201:
202:                }
203:
204:                // See if the return type is an object.  If it is then defer trying to
205:                // get the accessor until run-time.  Have to do it this way since
206:                // type comparisons are a little pointless.
207:                if (!retType.getName().equals(Object.class.getName())) {
208:
209:                    // The return type is NOT java.lang.Object, so now try and get the 
210:                    // accessor.
211:                    try {
212:
213:                        this .get = new Getter(this .acc, retType);
214:
215:                    } catch (Exception e) {
216:
217:                        throw new QueryParseException(
218:                                "Function: "
219:                                        + this 
220:                                        + " maps to method: "
221:                                        + this .function
222:                                        + " and has accessor: "
223:                                        + this .acc
224:                                        + " however no valid accessor has been found in return type: "
225:                                        + retType.getName(), e);
226:
227:                    }
228:
229:                }
230:
231:            }
232:
233:            private void getMethodFromHandlers(Query q, List handlers)
234:                    throws QueryParseException {
235:
236:                int s = handlers.size();
237:
238:                TreeMap ms = new TreeMap();
239:
240:                for (int i = 0; i < s; i++) {
241:
242:                    Object fh = handlers.get(i);
243:
244:                    this .getMethods(fh.getClass(), q, ms);
245:
246:                }
247:
248:                // Get the one with the highest score.
249:                if (ms.size() > 0) {
250:
251:                    this .function = (Method) ms.get(ms.lastKey());
252:
253:                    Class c = this .function.getDeclaringClass();
254:
255:                    // What a pain!
256:                    for (int i = 0; i < s; i++) {
257:
258:                        Object o = handlers.get(i);
259:
260:                        if (o.getClass().isAssignableFrom(c)) {
261:
262:                            this .handler = o;
263:
264:                        }
265:
266:                    }
267:
268:                }
269:
270:            }
271:
272:            private void findMethod(Query q) throws QueryParseException {
273:
274:                List fhs = q.getFunctionHandlers();
275:
276:                if (fhs != null) {
277:
278:                    this .getMethodFromHandlers(q, fhs);
279:
280:                }
281:
282:                if (this .function == null) {
283:
284:                    List dfhs = q.getDefaultFunctionHandlers();
285:
286:                    if (dfhs != null) {
287:
288:                        this .getMethodFromHandlers(q, dfhs);
289:
290:                    }
291:
292:                }
293:
294:            }
295:
296:            /**
297:             * Return the List of {@link Expression} objects that constitute the arguments
298:             * to the function, no guarantee is made here as to whether they have been inited.
299:             *
300:             * @return The List of {@link Expression} objects.
301:             */
302:            public List getParameters() {
303:
304:                return this .params;
305:
306:            }
307:
308:            public void setParameters(List ps) {
309:
310:                this .params = ps;
311:
312:            }
313:
314:            public void setName(String name) {
315:
316:                this .name = name;
317:
318:            }
319:
320:            public String getName() {
321:
322:                return this .name;
323:
324:            }
325:
326:            /**
327:             * Evaluate this function on the current object.  It should be noted that not
328:             * all functions will use the current object in their execution, functions from the
329:             * {@link org.josql.functions.GroupingFunctions} class are notable exceptions.
330:             *
331:             * @param o The current object.
332:             * @param q The Query object.
333:             * @return The result of evaluating the function.
334:             * @throws QueryExecutionException If something goes wrong during execution of the
335:             *                                 function or gaining the values to be used as arguments.
336:             */
337:            public Object evaluate(Object o, Query q)
338:                    throws QueryExecutionException {
339:
340:                // See if we have a fixed result.
341:                if (this .fixedResult) {
342:
343:                    // Evaluated once...
344:                    if (this .fixedValue != null) {
345:
346:                        return this .fixedValue;
347:
348:                    }
349:
350:                }
351:
352:                // Get the values for the parameters... if any...
353:                Object[] ps = null;
354:
355:                if (this .params != null) {
356:
357:                    int s = this .params.size();
358:
359:                    ps = new Object[s];
360:
361:                    for (int i = 0; i < s; i++) {
362:
363:                        Expression exp = (Expression) this .params.get(i);
364:
365:                        if (Expression.class.isAssignableFrom(this .function
366:                                .getParameterTypes()[i])) {
367:
368:                            // Leave this one alone.
369:                            ps[i] = exp;
370:
371:                        } else {
372:
373:                            // Eval this expression.
374:                            try {
375:
376:                                ps[i] = exp.getValue(o, q);
377:
378:                            } catch (Exception e) {
379:
380:                                throw new QueryExecutionException(
381:                                        "Unable to get parameter: " + i
382:                                                + " (\"" + exp.toString()
383:                                                + "\") for function: "
384:                                                + this .name, e);
385:
386:                            }
387:
388:                        }
389:
390:                    }
391:
392:                }
393:
394:                Object v = null;
395:
396:                try {
397:
398:                    v = this .function.invoke(this .handler, ps);
399:
400:                } catch (Exception e) {
401:
402:                    throw new QueryExecutionException(
403:                            "Unable to execute function: " + this .name + " (\""
404:                                    + this .toString() + "\") with values: "
405:                                    + Arrays.asList(ps), e);
406:
407:                }
408:
409:                if (v != null) {
410:
411:                    // See if we have an accessor.
412:                    if (this .acc != null) {
413:
414:                        // See if we have a Getter.
415:                        if (this .get == null) {
416:
417:                            // No getter, so now try and init it.  This assumes that the return
418:                            // type won't ever change!
419:                            try {
420:
421:                                this .get = new Getter(this .acc, v.getClass());
422:
423:                            } catch (Exception e) {
424:
425:                                throw new QueryExecutionException(
426:                                        "Unable to create accessor for: "
427:                                                + this .acc
428:                                                + " from return type: "
429:                                                + v.getClass().getName()
430:                                                + " after execution of function: "
431:                                                + this , e);
432:
433:                            }
434:
435:                        }
436:
437:                        try {
438:
439:                            v = this .get.getValue(v);
440:
441:                        } catch (Exception e) {
442:
443:                            throw new QueryExecutionException(
444:                                    "Unable to get value for accessor: "
445:                                            + this .acc + " from return type: "
446:                                            + v.getClass().getName()
447:                                            + " after execution of function: "
448:                                            + this , e);
449:
450:                        }
451:
452:                    }
453:
454:                }
455:
456:                if (this .fixedResult) {
457:
458:                    this .fixedValue = v;
459:
460:                }
461:
462:                return v;
463:
464:            }
465:
466:            /**
467:             * Return whether the evaluation of this function (see: {@link #evaluate(Object,Query)})
468:             * will result in a <code>true</code> value.
469:             * See: {@link ArithmeticExpression#isTrue(Object,Query)} for details of how this is 
470:             * determined.
471:             *
472:             * @param o The current object.
473:             * @param q The Query object.
474:             * @return <code>true</code> if the function return value evaluates to <code>true</code>.
475:             * @throws QueryExecutionException If something goes wrong with evaluating the function.
476:             */
477:            public boolean isTrue(Object o, Query q)
478:                    throws QueryExecutionException {
479:
480:                o = this .evaluate(o, q);
481:
482:                if (o == null) {
483:
484:                    return false;
485:
486:                }
487:
488:                if (Utilities.isNumber(o)) {
489:
490:                    return Utilities.getDouble(o) > 0;
491:
492:                }
493:
494:                if (o instanceof  Boolean) {
495:
496:                    return ((Boolean) o).booleanValue();
497:
498:                }
499:
500:                // Not null so return true...
501:                return true;
502:
503:            }
504:
505:            /**
506:             * Return a string representation of the function.
507:             * In the form: Name ( {@link Expression} [ , {@link Expression} ] )
508:             * 
509:             * @return A string representation of the function.
510:             */
511:            public String toString() {
512:
513:                StringBuffer buf = new StringBuffer();
514:
515:                buf.append(this .name);
516:                buf.append("(");
517:
518:                if (this .params != null) {
519:
520:                    for (int i = 0; i < this .params.size(); i++) {
521:
522:                        Expression p = (Expression) this .params.get(i);
523:
524:                        buf.append(p);
525:
526:                        if (i < (this .params.size() - 1)) {
527:
528:                            buf.append(",");
529:
530:                        }
531:
532:                    }
533:
534:                }
535:
536:                buf.append(")");
537:
538:                if (this .acc != null) {
539:
540:                    buf.append(".");
541:                    buf.append(this .acc);
542:
543:                }
544:
545:                if (this .isBracketed()) {
546:
547:                    buf.insert(0, "(");
548:
549:                    buf.append(")");
550:
551:                }
552:
553:                return buf.toString();
554:
555:            }
556:
557:            /**
558:             * Return whether the function will return a fixed result, this only
559:             * occurs iff all the arguments to the function also return a fixed result.
560:             *
561:             * @param q The Query object.
562:             */
563:            public boolean hasFixedResult(Query q) {
564:
565:                return this .fixedResult;
566:
567:            }
568:
569:            private int matchMethodArgs(Class[] methArgs, Query q)
570:                    throws QueryParseException {
571:
572:                // The score here helps in argument resolution, a more specific argument
573:                // match (that is NOT expression in the method args) will score higher and
574:                // thus is a better match.
575:                int score = 0;
576:
577:                for (int i = 0; i < methArgs.length; i++) {
578:
579:                    Class c = methArgs[i];
580:
581:                    Expression exp = (Expression) this .params.get(i);
582:
583:                    // See if the arg is object, which means "I can accept any type".
584:                    if (c.getClass().getName().equals(Object.class.getName())) {
585:
586:                        score += 1;
587:
588:                        continue;
589:
590:                    }
591:
592:                    // Now try and get the expected return type...
593:                    Class expC = exp.getExpectedReturnType(q);
594:
595:                    if (expC == null) {
596:
597:                        // Can't match this arg.
598:                        continue;
599:
600:                    } else {
601:
602:                        if (c.isAssignableFrom(expC)) {
603:
604:                            score += 2;
605:
606:                            continue;
607:
608:                        }
609:
610:                    }
611:
612:                    if (Expression.class.isAssignableFrom(c)) {
613:
614:                        score += 1;
615:
616:                        // This is a match... i.e. the arg is an expression and thus supported
617:                        // in a "special" way.
618:                        continue;
619:
620:                    }
621:
622:                    if ((Utilities.isNumber(expC))
623:                            && ((Utilities.isNumber(c)) || (c.getName()
624:                                    .equals(Object.class.getName())))) {
625:
626:                        score += 1;
627:
628:                        // This matches...
629:                        continue;
630:
631:                    }
632:
633:                    if ((Utilities.isPrimitiveClass(c))
634:                            && (Utilities.isPrimitiveClass(expC))) {
635:
636:                        // It is a primitive class as well, so now see if they are compatible.
637:                        if (Utilities.getPrimitiveClass(c).isAssignableFrom(
638:                                Utilities.getPrimitiveClass(expC))) {
639:
640:                            score += 1;
641:
642:                            // They are assignable...
643:                            continue;
644:
645:                        }
646:
647:                    }
648:
649:                    // See if the expression return type is an object... this "may" mean
650:                    // that we can match and it may not, it will be determined at runtime.
651:                    if (expC.getName().equals(Object.class.getName())) {
652:
653:                        score += 1;
654:
655:                        continue;
656:
657:                    }
658:
659:                    // If we are here then we can't match this arg type...
660:                    // No point checking any further...
661:                    return 0;
662:
663:                }
664:
665:                // All args can be matched.
666:                return score;
667:
668:            }
669:
670:            private void getMethods(Class c, Query q, Map matches)
671:                    throws QueryParseException {
672:
673:                Method[] meths = c.getMethods();
674:
675:                for (int i = 0; i < meths.length; i++) {
676:
677:                    Method m = meths[i];
678:
679:                    if (!m.getName().equals(this .name)) {
680:
681:                        continue;
682:
683:                    }
684:
685:                    // Make sure it's public...
686:                    if (!Modifier.isPublic(m.getModifiers())) {
687:
688:                        continue;
689:
690:                    }
691:
692:                    // Now check the args... sigh...
693:                    Class[] mpt = m.getParameterTypes();
694:
695:                    int ps = 0;
696:                    int fps = 0;
697:
698:                    if (mpt != null) {
699:
700:                        ps = mpt.length;
701:
702:                    }
703:
704:                    if (this .params != null) {
705:
706:                        fps = this .params.size();
707:
708:                    }
709:
710:                    if (ps != fps) {
711:
712:                        continue;
713:
714:                    }
715:
716:                    int score = this .matchMethodArgs(mpt, q);
717:
718:                    if (score > 0) {
719:
720:                        matches.put(Integer.valueOf(score), m);
721:
722:                    }
723:
724:                }
725:
726:            }
727:
728:        }
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