Source Code Cross Referenced for Statement.java in  » Workflow-Engines » osbl-1_0 » org » conform » mdl » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Workflow Engines » osbl 1_0 » org.conform.mdl 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        package org.conform.mdl;
002:
003:        /*
004:         * @(#)Statement.java	1.18 03/01/23
005:         *
006:         * Copyright 2003 Sun Microsystems, Inc. All rights reserved.
007:         * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
008:         */
009:
010:        import java.lang.reflect.*;
011:        import java.util.*;
012:        import java.beans.ExceptionListener;
013:
014:        /**
015:         * A <code>Statement</code> object represents a primitive statement
016:         * in which a single method is applied to a target and
017:         * a set of arguments - as in <code>"a.setFoo(b)"</code>.
018:         * Note that where this example uses names
019:         * to denote the target and its argument, a statement
020:         * object does not require a name space and is constructed with
021:         * the values themselves.
022:         * The statement object associates the named method
023:         * with its environment as a simple set of values:
024:         * the target and an array of argument values.
025:         *
026:         * @since 1.4
027:         *
028:         * @version 1.18 01/23/03
029:         * @author Philip Milne
030:         */
031:
032:        class Statement {
033:
034:            private static Object[] emptyArray = new Object[] {};
035:            private static HashMap methodCache = null;
036:
037:            static ExceptionListener defaultExceptionListener = new ExceptionListener() {
038:                public void exceptionThrown(Exception e) {
039:                    System.err.println(e);
040:                    // e.printStackTrace();
041:                    System.err.println("Continuing ...");
042:                }
043:            };
044:
045:            Object target;
046:            String methodName;
047:            Object[] arguments;
048:
049:            /**
050:             * Creates a new <code>Statement</code> object with a <code>target</code>,
051:             * <code>methodName</code> and <code>arguments</code> as per the parameters.
052:             *
053:             * @param target The target of this statement.
054:             * @param methodName The methodName of this statement.
055:             * @param arguments The arguments of this statement.
056:             *
057:             */
058:            public Statement(Object target, String methodName,
059:                    Object[] arguments) {
060:                this .target = target;
061:                this .methodName = methodName;
062:                this .arguments = (arguments == null) ? emptyArray : arguments;
063:            }
064:
065:            /**
066:             * Returns the target of this statement.
067:             *
068:             * @return The target of this statement.
069:             */
070:            public Object getTarget() {
071:                return target;
072:            }
073:
074:            /**
075:             * Returns the name of the method.
076:             *
077:             * @return The name of the method.
078:             */
079:            public String getMethodName() {
080:                return methodName;
081:            }
082:
083:            /**
084:             * Returns the arguments of this statement.
085:             *
086:             * @return the arguments of this statement.
087:             */
088:            public Object[] getArguments() {
089:                return arguments;
090:            }
091:
092:            /**
093:             * The execute method finds a method whose name is the same
094:             * as the methodName property, and invokes the method on
095:             * the target.
096:             *
097:             * When the target's class defines many methods with the given name
098:             * the implementation should choose the most specific method using
099:             * the algorithm specified in the Java Language Specification
100:             * (15.11). The dynamic class of the target and arguments are used
101:             * in place of the compile-time type information and, like the
102:             * <code>java.lang.reflect.Method</code> class itself, conversion between
103:             * primitive values and their associated wrapper classes is handled
104:             * internally.
105:             * <p>
106:             * The following method types are handled as special cases:
107:             * <ul>
108:             * <li>
109:             * Static methods may be called by using a class object as the target.
110:             * <li>
111:             * The reserved method name "new" may be used to call a class's constructor
112:             * as if all classes defined static "new" methods. Constructor invocations
113:             * are typically considered <code>Expression</code>s rather than <code>Statement</code>s
114:             * as they return a value.
115:             * <li>
116:             * The method names "get" and "set" defined in the <code>java.util.List</code>
117:             * interface may also be applied to array instances, mapping to
118:             * the static methods of the same name in the <code>Array</code> class.
119:             * </ul>
120:             */
121:            public void execute() throws Exception {
122:                invoke();
123:            }
124:
125:            /*pp*/static Class typeToClass(Class type) {
126:                return type.isPrimitive() ? typeNameToClass(type.getName())
127:                        : type;
128:
129:            }
130:
131:            /*pp*/static Class typeNameToClass(String typeName) {
132:                typeName = typeName.intern();
133:                if (typeName == "boolean")
134:                    return Boolean.class;
135:                if (typeName == "byte")
136:                    return Byte.class;
137:                if (typeName == "char")
138:                    return Character.class;
139:                if (typeName == "short")
140:                    return Short.class;
141:                if (typeName == "int")
142:                    return Integer.class;
143:                if (typeName == "long")
144:                    return Long.class;
145:                if (typeName == "float")
146:                    return Float.class;
147:                if (typeName == "double")
148:                    return Double.class;
149:                if (typeName == "void")
150:                    return Void.class;
151:                return null;
152:            }
153:
154:            private static Class typeNameToPrimitiveClass(String typeName) {
155:                typeName = typeName.intern();
156:                if (typeName == "boolean")
157:                    return boolean.class;
158:                if (typeName == "byte")
159:                    return byte.class;
160:                if (typeName == "char")
161:                    return char.class;
162:                if (typeName == "short")
163:                    return short.class;
164:                if (typeName == "int")
165:                    return int.class;
166:                if (typeName == "long")
167:                    return long.class;
168:                if (typeName == "float")
169:                    return float.class;
170:                if (typeName == "double")
171:                    return double.class;
172:                if (typeName == "void")
173:                    return void.class;
174:                return null;
175:            }
176:
177:            /*pp*/static Class primitiveTypeFor(Class wrapper) {
178:                if (wrapper == Boolean.class)
179:                    return Boolean.TYPE;
180:                if (wrapper == Byte.class)
181:                    return Byte.TYPE;
182:                if (wrapper == Character.class)
183:                    return Character.TYPE;
184:                if (wrapper == Short.class)
185:                    return Short.TYPE;
186:                if (wrapper == Integer.class)
187:                    return Integer.TYPE;
188:                if (wrapper == Long.class)
189:                    return Long.TYPE;
190:                if (wrapper == Float.class)
191:                    return Float.TYPE;
192:                if (wrapper == Double.class)
193:                    return Double.TYPE;
194:                if (wrapper == Void.class)
195:                    return Void.TYPE;
196:                return null;
197:            }
198:
199:            static Class classForName(String name)
200:                    throws ClassNotFoundException {
201:                // l.loadClass("int") fails.
202:                Class primitiveType = typeNameToPrimitiveClass(name);
203:                if (primitiveType != null) {
204:                    return primitiveType;
205:                }
206:                ClassLoader l = Thread.currentThread().getContextClassLoader();
207:                return l.loadClass(name);
208:            }
209:
210:            /**
211:             * Tests each element on the class arrays for assignability.
212:             *
213:             * @param argClasses arguments to be tested
214:             * @param argTypes arguments from Method
215:             * @return true if each class in argTypes is assignable from the
216:             *         corresponding class in argClasses.
217:             */
218:            private static boolean matchArguments(Class[] argClasses,
219:                    Class[] argTypes) {
220:                boolean match = (argClasses.length == argTypes.length);
221:                for (int j = 0; j < argClasses.length && match; j++) {
222:                    Class argType = argTypes[j];
223:                    if (argType.isPrimitive()) {
224:                        argType = typeToClass(argType);
225:                    }
226:                    // Consider null an instance of all classes.
227:                    if (argClasses[j] != null
228:                            && !(argType.isAssignableFrom(argClasses[j]))) {
229:                        match = false;
230:                    }
231:                }
232:                return match;
233:            }
234:
235:            /**
236:             * Tests each element on the class arrays for equality.
237:             *
238:             * @param argClasses arguments to be tested
239:             * @param argTypes arguments from Method
240:             * @return true if each class in argTypes is equal to the
241:             *         corresponding class in argClasses.
242:             */
243:            private static boolean matchExplicitArguments(Class[] argClasses,
244:                    Class[] argTypes) {
245:                boolean match = (argClasses.length == argTypes.length);
246:                for (int j = 0; j < argClasses.length && match; j++) {
247:                    Class argType = argTypes[j];
248:                    if (argType.isPrimitive()) {
249:                        argType = typeToClass(argType);
250:                    }
251:                    if (argClasses[j] != argType) {
252:                        match = false;
253:                    }
254:                }
255:                return match;
256:            }
257:
258:            // Pending: throw when the match is ambiguous.
259:            private static Method findPublicMethod(Class declaringClass,
260:                    String methodName, Class[] argClasses) {
261:                // Many methods are "getters" which take no arguments.
262:                // This permits the following optimisation which
263:                // avoids the expensive call to getMethods().
264:                if (argClasses.length == 0) {
265:                    try {
266:                        return declaringClass.getMethod(methodName, argClasses);
267:                    } catch (NoSuchMethodException e) {
268:                        return null;
269:                    }
270:                }
271:                // logger.finest("getMethods " + declaringClass + " for " + methodName);
272:                Method[] methods = declaringClass.getMethods();
273:                ArrayList list = new ArrayList();
274:                for (int i = 0; i < methods.length; i++) {
275:                    // Collect all the methods which match the signature.
276:                    Method method = methods[i];
277:                    if (method.getName().equals(methodName)) {
278:                        if (matchArguments(argClasses, method
279:                                .getParameterTypes())) {
280:                            list.add(method);
281:                        }
282:                    }
283:                }
284:                if (list.size() > 0) {
285:                    if (list.size() == 1) {
286:                        return (Method) list.get(0);
287:                    } else {
288:                        ListIterator iterator = list.listIterator();
289:                        Method method;
290:                        while (iterator.hasNext()) {
291:                            method = (Method) iterator.next();
292:                            if (matchExplicitArguments(argClasses, method
293:                                    .getParameterTypes())) {
294:                                return method;
295:                            }
296:                        }
297:                        // This list is valid. Should return something.
298:                        return (Method) list.get(0);
299:                    }
300:                }
301:                return null;
302:            }
303:
304:            // Pending: throw when the match is ambiguous.
305:            private static Method findMethod(Class targetClass,
306:                    String methodName, Class[] argClasses) {
307:                Method m = findPublicMethod(targetClass, methodName, argClasses);
308:                if (m != null
309:                        && Modifier.isPublic(m.getDeclaringClass()
310:                                .getModifiers())) {
311:                    return m;
312:                }
313:
314:                /*
315:                Search the interfaces for a public version of this method.
316:
317:                Example: the getKeymap() method of a JTextField
318:                returns a package private implementation of the
319:                of the public Keymap interface. In the Keymap
320:                interface there are a number of "properties" one
321:                being the "resolveParent" property implied by the
322:                getResolveParent() method. This getResolveParent()
323:                cannot be called reflectively because the class
324:                itself is not public. Instead we search the class's
325:                interfaces and find the getResolveParent()
326:                method of the Keymap interface - on which invoke
327:                may be applied without error.
328:
329:                So in :-
330:
331:                    JTextField o = new JTextField("Hello, world");
332:                    Keymap km = o.getKeymap();
333:                    Method m1 = km.getClass().getMethod("getResolveParent", new Class[0]);
334:                    Method m2 = Keymap.class.getMethod("getResolveParent", new Class[0]);
335:
336:                Methods m1 and m2 are different. The invocation of method
337:                m1 unconditionally throws an IllegalAccessException where
338:                the invocation of m2 will invoke the implementation of the
339:                method. Note that (ignoring the overloading of arguments)
340:                there is only one implementation of the named method which
341:                may be applied to this target.
342:                 */
343:                for (Class type = targetClass; type != null; type = type
344:                        .getSuperclass()) {
345:                    Class[] interfaces = type.getInterfaces();
346:                    for (int i = 0; i < interfaces.length; i++) {
347:                        m = findPublicMethod(interfaces[i], methodName,
348:                                argClasses);
349:                        if (m != null) {
350:                            return m;
351:                        }
352:                    }
353:                }
354:                return null;
355:            }
356:
357:            private static class Signature {
358:                Class targetClass;
359:                String methodName;
360:                Class[] argClasses;
361:
362:                public Signature(Class targetClass, String methodName,
363:                        Class[] argClasses) {
364:                    this .targetClass = targetClass;
365:                    this .methodName = methodName;
366:                    this .argClasses = argClasses;
367:                }
368:
369:                public boolean equals(Object o2) {
370:                    Statement.Signature that = (Statement.Signature) o2;
371:                    if (!(targetClass == that.targetClass)) {
372:                        return false;
373:                    }
374:                    if (!(methodName.equals(that.methodName))) {
375:                        return false;
376:                    }
377:                    if (argClasses.length != that.argClasses.length) {
378:                        return false;
379:                    }
380:                    for (int i = 0; i < argClasses.length; i++) {
381:                        if (!(argClasses[i] == that.argClasses[i])) {
382:                            return false;
383:                        }
384:                    }
385:                    return true;
386:                }
387:
388:                // Pending(milne) Seek advice an a suitable hash function to use here.
389:                public int hashCode() {
390:                    return targetClass.hashCode() * 35 + methodName.hashCode();
391:                }
392:            }
393:
394:            /** A wrapper to findMethod(), which will cache its results if
395:             * isCaching() returns true. See clear().
396:             */
397:            static Method getMethod(Class targetClass, String methodName,
398:                    Class[] argClasses) {
399:                if (!isCaching()) {
400:                    return findMethod(targetClass, methodName, argClasses);
401:                }
402:                Object signature = new Statement.Signature(targetClass,
403:                        methodName, argClasses);
404:                Method m = (Method) methodCache.get(signature);
405:                if (m != null) {
406:                    // logger.finest("findMethod found " + methodName + " for " + targetClass);
407:                    return m;
408:                }
409:                // logger.finest("findMethod searching " + targetClass + " for " + methodName);
410:                m = findMethod(targetClass, methodName, argClasses);
411:                if (m != null) {
412:                    methodCache.put(signature, m);
413:                }
414:                return m;
415:            }
416:
417:            static void setCaching(boolean b) {
418:                methodCache = b ? new HashMap() : null;
419:            }
420:
421:            private static boolean isCaching() {
422:                return methodCache != null;
423:            }
424:
425:            Object invoke() throws Exception {
426:                // logger.finest("Invoking: " + toString());
427:                Object target = getTarget();
428:                String methodName = getMethodName();
429:                Object[] arguments = getArguments();
430:                // Class.forName() won't load classes outside
431:                // of core from a class inside core. Special
432:                // case this method.
433:                if (target == Class.class && methodName == "forName") {
434:                    return classForName((String) arguments[0]);
435:                }
436:                Class[] argClasses = new Class[arguments.length];
437:                for (int i = 0; i < arguments.length; i++) {
438:                    argClasses[i] = (arguments[i] == null) ? null
439:                            : arguments[i].getClass();
440:                }
441:
442:                AccessibleObject m = null;
443:                if (target instanceof  Class) {
444:                    /*
445:                    For class methods, simluate the effect of a meta class
446:                    by taking the union of the static methods of the
447:                    actual class, with the instance methods of "Class.class"
448:                    and the overloaded "newInstance" methods defined by the
449:                    constructors.
450:                    This way "System.class", for example, will perform both
451:                    the static method getProperties() and the instance method
452:                    getSuperclass() defined in "Class.class".
453:                     */
454:                    if (methodName == "new") {
455:                        methodName = "newInstance";
456:                    }
457:                    // Provide a short conform for array instantiation by faking an nary-constructor.
458:                    if (methodName == "newInstance"
459:                            && ((Class) target).isArray()) {
460:                        Object result = Array.newInstance(((Class) target)
461:                                .getComponentType(), arguments.length);
462:                        for (int i = 0; i < arguments.length; i++) {
463:                            Array.set(result, i, arguments[i]);
464:                        }
465:                        return result;
466:                    }
467:                    if (methodName == "newInstance" && arguments.length != 0) {
468:                        // The Character class, as of 1.4, does not have a constructor
469:                        // which takes a String. All of the other "wrapper" classes
470:                        // for Java's primitive types have a String constructor so we
471:                        // fake such a constructor here so that this special case can be
472:                        // ignored elsewhere.
473:                        if (target == Character.class && arguments.length == 1
474:                                && argClasses[0] == String.class) {
475:                            return new Character(((String) arguments[0])
476:                                    .charAt(0));
477:                        }
478:                        Constructor[] constructors = ((Class) target)
479:                                .getConstructors();
480:                        // PENDING: Implement the resolutuion of ambiguities properly.
481:                        for (int i = 0; i < constructors.length; i++) {
482:                            Constructor constructor = constructors[i];
483:                            if (matchArguments(argClasses, constructor
484:                                    .getParameterTypes())) {
485:                                m = constructor;
486:                            }
487:                        }
488:                    }
489:                    if (m == null) {
490:                        m = getMethod((Class) target, methodName, argClasses);
491:                    }
492:                    if (m == null) {
493:                        m = getMethod(Class.class, methodName, argClasses);
494:                    }
495:                } else {
496:                    /*
497:                    This special casing of arrays is not necessary, but makes files
498:                    involving arrays much shorter and simplifies the archiving infrastrcure.
499:                    The Array.set() method introduces an unusual idea - that of a static method
500:                    changing the state of an instance. Normally statements with side
501:                    effects on objects are instance methods of the objects themselves
502:                    and we reinstate this rule (perhaps temporarily) by special-casing arrays.
503:                     */
504:                    if (target.getClass().isArray()
505:                            && (methodName == "set" || methodName == "get")) {
506:                        int index = ((Integer) arguments[0]).intValue();
507:                        if (methodName == "get") {
508:                            return Array.get(target, index);
509:                        } else {
510:                            Array.set(target, index, arguments[1]);
511:                            return null;
512:                        }
513:                    }
514:                    m = getMethod(target.getClass(), methodName, argClasses);
515:                }
516:                if (m != null) {
517:                    // System.err.println("Calling \"" + methodName + "\"" + " on " + ((o == null) ? null : target.getClass()));
518:                    try {
519:                        if (m instanceof  Method) {
520:                            return ((Method) m).invoke(target, arguments);
521:                        } else {
522:                            return ((Constructor) m).newInstance(arguments);
523:                        }
524:                    } catch (IllegalAccessException iae) {
525:                        throw new IllegalAccessException(toString());
526:                    } catch (InvocationTargetException ite) {
527:                        Throwable te = ite.getTargetException();
528:                        if (te instanceof  Exception) {
529:                            throw (Exception) te;
530:                        } else {
531:                            throw ite;
532:                        }
533:                    }
534:                }
535:                throw new NoSuchMethodException(toString());
536:            }
537:
538:            /*pp*/String instanceName(Object instance) {
539:                return (instance != null && instance.getClass() == String.class) ? "\""
540:                        + (String) instance + "\""
541:                        : NameGenerator.instanceName(instance);
542:            }
543:
544:            /**
545:             * Prints the value of this statement using a Java-style syntax.
546:             */
547:            public String toString() {
548:                // Respect a subclass's implementation here.
549:                Object target = getTarget();
550:                String methodName = getMethodName();
551:                Object[] arguments = getArguments();
552:
553:                StringBuffer result = new StringBuffer(instanceName(target)
554:                        + "." + methodName + "(");
555:                int n = arguments.length;
556:                for (int i = 0; i < n; i++) {
557:                    result.append(instanceName(arguments[i]));
558:                    if (i != n - 1) {
559:                        result.append(", ");
560:                    }
561:                }
562:                result.append(");");
563:                return result.toString();
564:            }
565:        }
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