Source Code Cross Referenced for ReflectAccess.java in  » Scripting » InstantJ » instantj » reflect » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Scripting » InstantJ » instantj.reflect 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /**
002:         * InstantJ
003:         * 
004:         * Copyright (C) 2002 Nils Meier
005:         * 
006:         * This library is free software; you can redistribute it and/or
007:         * modify it under the terms of the GNU Lesser General Public
008:         * License as published by the Free Software Foundation; either
009:         * version 2.1 of the License, or (at your option) any later version.
010:         * 
011:         * This library is distributed in the hope that it will be useful,
012:         * but WITHOUT ANY WARRANTY; without even the implied warranty of
013:         * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014:         * Lesser General Public License for more details.
015:         * 
016:         */package instantj.reflect;
017:
018:        import java.lang.reflect.Constructor;
019:        import java.lang.reflect.Field;
020:        import java.lang.reflect.Method;
021:        import java.lang.reflect.InvocationTargetException;
022:
023:        /**
024:         * The class providing reflection operations - have a look at the
025:         * list of methods to find out what this thing provides.
026:         *
027:         * @author <A href="mailto:nils@meiers.net">Nils Meier</A>
028:         */
029:        public class ReflectAccess {
030:
031:            /** the singleton instance */
032:            private static ReflectAccess singleton = new ReflectAccess();
033:
034:            /** the usual getter */
035:            private static String GET = "get";
036:
037:            /** the 'is' getter */
038:            private static String IS = "is";
039:
040:            /** the usual setter */
041:            private static String SET = "set";
042:
043:            /** an empty class array */
044:            private final static Class[] EMPTY_CLASS_ARRAY = new Class[0];
045:
046:            /** a one-Integer class array */
047:            private final static Class[] ONE_INT_CLASS_ARRAY = new Class[] { Integer.TYPE };
048:
049:            /** an empty object array */
050:            private final static Object[] EMPTY_OBJECT_ARRAY = new Object[0];
051:
052:            /** a one-String class array */
053:            private final static Class[] ONE_OBJECT_CLASS_ARRAY = new Class[] { Object.class };
054:
055:            /**
056:             * Returns a getter/setter method name for given property
057:             */
058:            public String calcAccessor(String prefix, String property) {
059:                return prefix + property.substring(0, 1).toUpperCase()
060:                        + property.substring(1);
061:            }
062:
063:            /**
064:             * Constructor
065:             */
066:            private ReflectAccess() {
067:            }
068:
069:            /**
070:             * Singleton access
071:             */
072:            public static ReflectAccess getInstance() {
073:                return singleton;
074:            }
075:
076:            /**
077:             * Helper which calculates a Class array for given Object array
078:             */
079:            public Class[] calcClassesFromObjects(Object[] args) {
080:
081:                // The empty case
082:                if (args.length == 0) {
083:                    return EMPTY_CLASS_ARRAY;
084:                }
085:
086:                // Looping required
087:                Class[] result = new Class[args.length];
088:                for (int i = 0; i < result.length; i++) {
089:                    if (args[i] != null) {
090:                        result[i] = args[i].getClass();
091:                    } else {
092:                        result[i] = Object.class;
093:                    }
094:                }
095:
096:                // Done
097:                return result;
098:            }
099:
100:            /**
101:             * Returns the class name without package for given class
102:             */
103:            public String calcClassNameOf(Class theClass) {
104:                String name = theClass.getName();
105:                int pkg = name.lastIndexOf('.');
106:                if (pkg < 0) {
107:                    return name;
108:                }
109:                return name.substring(pkg + 1);
110:            }
111:
112:            /**
113:             * Returns a Method for the given object
114:             */
115:            public Method calcMethodFor(Object object, String method,
116:                    Class[] args) throws NoSuchMethodException {
117:                // Hmmm, should this be getDeclaredMethod or getMethod?
118:                return object.getClass().getMethod(method, args);
119:            }
120:
121:            /**
122:             * Returns the package name without classname for given class
123:             */
124:            public String calcPkgNameOf(Class theClass) {
125:
126:                String name = theClass.getName();
127:                int pkg = name.lastIndexOf('.');
128:                if (pkg < 0)
129:                    return "";
130:
131:                return name.substring(0, pkg);
132:            }
133:
134:            /**
135:             * Invokes a getter on given object - the property XYZ
136:             * has to reflect the object's methods getXYZ or isXYZ
137:             *
138:             * Mental Note: if an inner type is 'private static' AND
139:             * has a public method, an attempt to invoke it will lead
140:             * to an IllegalAccessException (Arrays.asList() for example
141:             * returns a type 'Arrays$ArrayList' that is 'private static')
142:             * in JDK 1.3
143:             */
144:            public Object invokeGetter(Object object, String property)
145:                    throws IllegalPropertyException,
146:                    InaccessiblePropertyException {
147:
148:                IllegalPropertyException retry = null;
149:                while (true) {
150:
151:                    try {
152:
153:                        // The method to call
154:                        String accessor = (retry == null ? calcAccessor(GET,
155:                                property) : calcAccessor(IS, property));
156:
157:                        // Do the call				
158:                        return invoke(object, accessor, EMPTY_OBJECT_ARRAY);
159:
160:                    } catch (NoSuchMethodException e) {
161:                        if (retry != null)
162:                            throw retry;
163:                        retry = new IllegalPropertyException(
164:                                "getter doesn't exist", object, property);
165:                    } catch (IllegalAccessException e) {
166:                        throw new InaccessiblePropertyException(
167:                                "getter couldn't be accessed", object, property);
168:                    } catch (InvocationTargetException e) {
169:                        throw new InaccessiblePropertyException(
170:                                "getter failed", object, property, e
171:                                        .getTargetException());
172:                    }
173:
174:                }
175:
176:            }
177:
178:            /**
179:             * Invokes a setter on given object
180:             */
181:            public void invokeSetter(Object object, String property, Object arg)
182:                    throws IllegalPropertyException,
183:                    InaccessiblePropertyException {
184:
185:                try {
186:
187:                    // The method to call
188:                    String accessor = calcAccessor(SET, property);
189:
190:                    // Do the call
191:                    invoke(object, accessor, calcArrayWrap(arg));
192:
193:                } catch (NoSuchMethodException e) {
194:                    throw new IllegalPropertyException("setter doesn't exist",
195:                            object, property);
196:                } catch (IllegalAccessException e) {
197:                    throw new InaccessiblePropertyException(
198:                            "setter couldn't be accessed", object, property);
199:                } catch (InvocationTargetException e) {
200:                    throw new InaccessiblePropertyException("setter failed",
201:                            object, property, e.getTargetException());
202:                }
203:
204:            }
205:
206:            /**
207:             * Helper that wraps an Object into an Array
208:             */
209:            public Object[] calcArrayWrap(Object object) {
210:                return new Object[] { object };
211:            }
212:
213:            /**
214:             * Sets a field on given object
215:             * @param object the instance to set property on
216:             * @param property the property to set on the instance
217:             * @param value the value to set
218:             */
219:            public void setField(Object object, String property, Object value)
220:                    throws IllegalPropertyException,
221:                    InaccessiblePropertyException {
222:                setField(object, property, value, false);
223:            }
224:
225:            /**
226:             * Sets a field on given object
227:             * @param object the instance to set property on
228:             * @param property the property to set on the instance
229:             * @param value the value to set
230:             * @param wrapValueIfNeeded whether to try to wrap a value with a field-type one-argument-constructor if necessary
231:             */
232:            public void setField(Object object, String property, Object value,
233:                    boolean wrapValueIfNeeded) throws IllegalPropertyException,
234:                    InaccessiblePropertyException {
235:
236:                String fieldType = "<UNKNOWN>";
237:                try {
238:
239:                    // Here's the target's type
240:                    Class type = object.getClass();
241:
242:                    // .. and the field we're going for
243:                    Field f = type.getDeclaredField(property);
244:                    fieldType = f.getType().getName();
245:
246:                    // .. last change to adjust the type
247:                    if (wrapValueIfNeeded
248:                            && (!f.getType().isAssignableFrom(value.getClass()))) {
249:                        value = calcWrapping(value, f.getType());
250:                    }
251:
252:                    // .. and the actual set
253:                    f.set(object, value);
254:
255:                    // Done
256:                } catch (NoSuchFieldException e) {
257:                    throw new IllegalPropertyException("field doesn't exist",
258:                            object, property);
259:                } catch (IllegalAccessException e) {
260:                    throw new InaccessiblePropertyException(
261:                            "field couldn't be accessed", object, property);
262:                } catch (IllegalArgumentException e) {
263:                    throw new IllegalPropertyException(
264:                            "field type "
265:                                    + fieldType
266:                                    + " doesn't match value type "
267:                                    + value.getClass().getName()
268:                                    + " and wrapping with single-argument constructor was unsuccessfull",
269:                            object, property);
270:                }
271:
272:            }
273:
274:            /**
275:             * Invokes a given method on given object
276:             */
277:            public Object invoke(Object instance, String method, Object[] args)
278:                    throws NoSuchMethodException, IllegalAccessException,
279:                    InvocationTargetException {
280:
281:                // Prepare the argument type array
282:                Class[] argTypes = new Class[args.length];
283:                for (int i = 0; i < argTypes.length; i++) {
284:                    argTypes[i] = args[i].getClass();
285:                }
286:
287:                // Calc the method
288:                Method m = calcMethodFor(instance, method, argTypes);
289:
290:                // Do the call
291:                Object result = m.invoke(instance, args);
292:
293:                // Done
294:                return result;
295:
296:            }
297:
298:            /**
299:             * Calculates a type for given name
300:             * 
301:             * @param name the type's name
302:             */
303:            public Class calcClassFromName(String name)
304:                    throws IllegalArgumentException {
305:
306:                // Check the usual suspects
307:                if (Boolean.TYPE.getName().equals(name))
308:                    return Boolean.TYPE;
309:                if (Integer.TYPE.getName().equals(name))
310:                    return Integer.TYPE;
311:                if (Short.TYPE.getName().equals(name))
312:                    return Short.TYPE;
313:                if (Character.TYPE.getName().equals(name))
314:                    return Character.TYPE;
315:                if ("String".equals(name))
316:                    return String.class;
317:                if ("Boolean".equals(name))
318:                    return Boolean.class;
319:                if ("Integer".equals(name))
320:                    return Integer.class;
321:                if ("Date".equals(name))
322:                    return java.util.Date.class;
323:
324:                // otherwise load it
325:                try {
326:                    return Class.forName(name.toString());
327:                } catch (Throwable t) {
328:                    throw new IllegalArgumentException(
329:                            "Couldn't resolve type for name " + name);
330:                }
331:
332:                // Done
333:            }
334:
335:            /**
336:             * Tries to wrap a given object in an instance of given target
337:             * type by calling that type's one-argument-constructor.
338:             * @param object the to be wrapped
339:             * @param target the wrapper type
340:             */
341:            public Object calcWrapping(Object object, Class target)
342:                    throws IllegalArgumentException {
343:
344:                // Check for primitive wrappers
345:                if (Boolean.TYPE.equals(target)) {
346:                    target = Boolean.class;
347:                }
348:                if (Integer.TYPE.equals(target)) {
349:                    target = Integer.class;
350:                }
351:                if (Short.TYPE.equals(target)) {
352:                    target = Short.class;
353:                }
354:                if (Character.TYPE.equals(target)) {
355:                    target = Character.class;
356:                }
357:                if (Long.TYPE.equals(target)) {
358:                    target = Long.class;
359:                }
360:                if (Double.TYPE.equals(target)) {
361:                    target = Double.class;
362:                }
363:                if (Float.TYPE.equals(target)) {
364:                    target = Float.class;
365:                }
366:
367:                // Maybe it's assignable already
368:                if (target.isAssignableFrom(object.getClass()))
369:                    return object;
370:
371:                // Check the one-argument-constructor
372:                try {
373:                    Constructor constructor = target
374:                            .getConstructor(new Class[] { object.getClass() });
375:                    return constructor.newInstance(new Object[] { object });
376:                } catch (Throwable t) {
377:                    throw new IllegalArgumentException("Couldn't wrap "
378:                            + object.getClass() + " in an instance of "
379:                            + target);
380:                }
381:
382:                // Done
383:            }
384:
385:        }
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