Source Code Cross Referenced for Method.java in  » 6.0-JDK-Modules » j2me » java » lang » reflect » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » 6.0 JDK Modules » j2me » java.lang.reflect 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         * @(#)Method.java	1.30 02/08/19
003:         *
004:         * Copyright  1990-2006 Sun Microsystems, Inc. All Rights Reserved.  
005:         * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER  
006:         *   
007:         * This program is free software; you can redistribute it and/or  
008:         * modify it under the terms of the GNU General Public License version  
009:         * 2 only, as published by the Free Software Foundation.   
010:         *   
011:         * This program is distributed in the hope that it will be useful, but  
012:         * WITHOUT ANY WARRANTY; without even the implied warranty of  
013:         * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU  
014:         * General Public License version 2 for more details (a copy is  
015:         * included at /legal/license.txt).   
016:         *   
017:         * You should have received a copy of the GNU General Public License  
018:         * version 2 along with this work; if not, write to the Free Software  
019:         * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  
020:         * 02110-1301 USA   
021:         *   
022:         * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa  
023:         * Clara, CA 95054 or visit www.sun.com if you need additional  
024:         * information or have any questions. 
025:         *
026:         */
027:
028:        package java.lang.reflect;
029:
030:        import sun.misc.CVM;
031:
032:        /**
033:         * A <code>Method</code> provides information about, and access to, a single method
034:         * on a class or interface.  The reflected method may be a class method
035:         * or an instance method (including an abstract method).
036:         *
037:         * <p>A <code>Method</code> permits widening conversions to occur when matching the
038:         * actual parameters to invokewith the underlying method's formal
039:         * parameters, but it throws an <code>IllegalArgumentException</code> if a
040:         * narrowing conversion would occur.
041:         *
042:         * @see Member
043:         * @see java.lang.Class
044:         * @see java.lang.Class#getMethods()
045:         * @see java.lang.Class#getMethod(String, Class[])
046:         * @see java.lang.Class#getDeclaredMethods()
047:         * @see java.lang.Class#getDeclaredMethod(String, Class[])
048:         *
049:         * @author Nakul Saraiya
050:         */
051:        public final class Method extends AccessibleObject implements  Member {
052:
053:            private Class clazz;
054:            private int slot;
055:            private String name;
056:            private Class returnType;
057:            private Class[] parameterTypes;
058:            private Class[] exceptionTypes;
059:            private int modifiers;
060:
061:            /**
062:             * Constructor.  Only the Java Virtual Machine may construct a Method.
063:             */
064:            private Method() {
065:            }
066:
067:            /**
068:             * Returns the <code>Class</code> object representing the class or interface
069:             * that declares the method represented by this <code>Method</code> object.
070:             */
071:            public Class getDeclaringClass() {
072:                return clazz;
073:            }
074:
075:            /**
076:             * Returns the name of the method represented by this <code>Method</code> 
077:             * object, as a <code>String</code>.
078:             */
079:            public String getName() {
080:                return name;
081:            }
082:
083:            /**
084:             * Returns the Java language modifiers for the method represented
085:             * by this <code>Method</code> object, as an integer. The <code>Modifier</code> class should
086:             * be used to decode the modifiers.
087:             *
088:             * @see Modifier
089:             */
090:            public int getModifiers() {
091:                return modifiers;
092:            }
093:
094:            /**
095:             * Returns a <code>Class</code> object that represents the formal return type
096:             * of the method represented by this <code>Method</code> object.
097:             * 
098:             * @return the return type for the method this object represents
099:             */
100:            public Class getReturnType() {
101:                return returnType;
102:            }
103:
104:            /**
105:             * Returns an array of <code>Class</code> objects that represent the formal
106:             * parameter types, in declaration order, of the method
107:             * represented by this <code>Method</code> object.  Returns an array of length
108:             * 0 if the underlying method takes no parameters.
109:             * 
110:             * @return the parameter types for the method this object
111:             * represents
112:             */
113:            public Class[] getParameterTypes() {
114:                return copy(parameterTypes);
115:            }
116:
117:            /**
118:             * Returns an array of <code>Class</code> objects that represent 
119:             * the types of the exceptions declared to be thrown
120:             * by the underlying method
121:             * represented by this <code>Method</code> object.  Returns an array of length
122:             * 0 if the method declares no exceptions in its <code>throws</code> clause.
123:             * 
124:             * @return the exception types declared as being thrown by the
125:             * method this object represents
126:             */
127:            public Class[] getExceptionTypes() {
128:                return copy(exceptionTypes);
129:            }
130:
131:            /**
132:             * Compares this <code>Method</code> against the specified object.  Returns
133:             * true if the objects are the same.  Two <code>Methods</code> are the same if
134:             * they were declared by the same class and have the same name
135:             * and formal parameter types and return type.
136:             */
137:            public boolean equals(Object obj) {
138:                if (obj != null && obj instanceof  Method) {
139:                    Method other = (Method) obj;
140:                    if ((getDeclaringClass() == other.getDeclaringClass())
141:                            && (getName().equals(other.getName()))) {
142:                        /* Avoid unnecessary cloning */
143:                        Class[] params1 = parameterTypes;
144:                        Class[] params2 = other.parameterTypes;
145:                        if (params1.length == params2.length) {
146:                            for (int i = 0; i < params1.length; i++) {
147:                                if (params1[i] != params2[i])
148:                                    return false;
149:                            }
150:                            return true;
151:                        }
152:                    }
153:                }
154:                return false;
155:            }
156:
157:            /**
158:             * Returns a hashcode for this <code>Method</code>.  The hashcode is computed
159:             * as the exclusive-or of the hashcodes for the underlying
160:             * method's declaring class name and the method's name.
161:             */
162:            public int hashCode() {
163:                return getDeclaringClass().getName().hashCode()
164:                        ^ getName().hashCode();
165:            }
166:
167:            /**
168:             * Returns a string describing this <code>Method</code>.  The string is
169:             * formatted as the method access modifiers, if any, followed by
170:             * the method return type, followed by a space, followed by the
171:             * class declaring the method, followed by a period, followed by
172:             * the method name, followed by a parenthesized, comma-separated
173:             * list of the method's formal parameter types. If the method
174:             * throws checked exceptions, the parameter list is followed by a
175:             * space, followed by the word throws followed by a
176:             * comma-separated list of the thrown exception types.
177:             * For example:
178:             * <pre>
179:             *    public boolean java.lang.Object.equals(java.lang.Object)
180:             * </pre>
181:             *
182:             * <p>The access modifiers are placed in canonical order as
183:             * specified by "The Java Language Specification".  This is
184:             * <tt>public</tt>, <tt>protected</tt> or <tt>private</tt> first,
185:             * and then other modifiers in the following order:
186:             * <tt>abstract</tt>, <tt>static</tt>, <tt>final</tt>,
187:             * <tt>synchronized</tt> <tt>native</tt>.
188:             */
189:            public String toString() {
190:                try {
191:                    StringBuffer sb = new StringBuffer();
192:                    int mod = getModifiers();
193:                    if (mod != 0) {
194:                        sb.append(Modifier.toString(mod) + " ");
195:                    }
196:                    sb.append(Field.getTypeName(getReturnType()) + " ");
197:                    sb.append(Field.getTypeName(getDeclaringClass()) + ".");
198:                    sb.append(getName() + "(");
199:                    Class[] params = parameterTypes; // avoid clone
200:                    for (int j = 0; j < params.length; j++) {
201:                        sb.append(Field.getTypeName(params[j]));
202:                        if (j < (params.length - 1))
203:                            sb.append(",");
204:                    }
205:                    sb.append(")");
206:                    Class[] exceptions = exceptionTypes; // avoid clone
207:                    if (exceptions.length > 0) {
208:                        sb.append(" throws ");
209:                        for (int k = 0; k < exceptions.length; k++) {
210:                            sb.append(exceptions[k].getName());
211:                            if (k < (exceptions.length - 1))
212:                                sb.append(",");
213:                        }
214:                    }
215:                    return sb.toString();
216:                } catch (Exception e) {
217:                    return "<" + e + ">";
218:                }
219:            }
220:
221:            /** An internal class to be able to distinguish between an
222:              IllegalArgumentException because of incorrectly-typed objects in
223:              the argument array to Method.invoke() and one thrown by the
224:              invoked method. NOTE: do not change the name of this class as it
225:              is referenced by name in reflect.c, utils.c and elsewhere. */
226:            private static class ArgumentException extends Exception {
227:            }
228:
229:            /** An internal class to be able to distinguish between an
230:              IllegalAccessException because of an invalid attempt to invoke a
231:              protected or private method in Method.invoke() and one thrown by
232:              the invoked method. NOTE: do not change the name of this class
233:              as it is referenced by name in reflect.c, utils.c and
234:              elsewhere. */
235:            private static class AccessException extends Exception {
236:            }
237:
238:            /**
239:             * Invokes the underlying method represented by this <code>Method</code> 
240:             * object, on the specified object with the specified parameters.
241:             * Individual parameters are automatically unwrapped to match
242:             * primitive formal parameters, and both primitive and reference
243:             * parameters are subject to method invocation conversions as
244:             * necessary.
245:             *
246:             * <p>If the underlying method is static, then the specified <code>obj</code> 
247:             * argument is ignored. It may be null.
248:             *
249:             * <p>If the number of formal parameters required by the underlying method is
250:             * 0, the supplied <code>args</code> array may be of length 0 or null.
251:             *
252:             * <p>If the underlying method is an instance method, it is invoked
253:             * using dynamic method lookup as documented in The Java Language
254:             * Specification, Second Edition, section 15.12.4.4; in particular,
255:             * overriding based on the runtime type of the target object will occur.
256:             *
257:             * <p>If the underlying method is static, the class that declared
258:             * the method is initialized if it has not already been initialized.
259:             *
260:             * <p>If the method completes normally, the value it returns is
261:             * returned to the caller of invoke; if the value has a primitive
262:             * type, it is first appropriately wrapped in an object. If the
263:             * underlying method return type is void, the invocation returns
264:             * null.
265:             *
266:             * @param obj  the object the underlying method is invoked from
267:             * @param args the arguments used for the method call
268:             * @return the result of dispatching the method represented by
269:             * this object on <code>obj</code> with parameters
270:             * <code>args</code>
271:             *
272:             * @exception IllegalAccessException    if this <code>Method</code> object
273:             *              enforces Java language access control and the underlying
274:             *              method is inaccessible.
275:             * @exception IllegalArgumentException  if the method is an
276:             *              instance method and the specified object argument
277:             *              is not an instance of the class or interface
278:             *              declaring the underlying method (or of a subclass
279:             *              or implementor thereof); if the number of actual
280:             *              and formal parameters differ; if an unwrapping
281:             *              conversion for primitive arguments fails; or if,
282:             *              after possible unwrapping, a parameter value
283:             *              cannot be converted to the corresponding formal
284:             *              parameter type by a method invocation conversion.
285:             * @exception InvocationTargetException if the underlying method
286:             *              throws an exception.
287:             * @exception NullPointerException      if the specified object is null
288:             *              and the method is an instance method.
289:             * @exception ExceptionInInitializerError if the initialization
290:             * provoked by this method fails.
291:             */
292:            public Object invoke(Object obj, Object[] args)
293:                    throws IllegalAccessException, IllegalArgumentException,
294:                    InvocationTargetException {
295:                Object retval = null;
296:
297:                if ((obj == null) && ((getModifiers() & Modifier.STATIC) == 0)) {
298:                    throw new NullPointerException("Method.invoke()");
299:                }
300:
301:                /* Null pointer is acceptable for args if no arguments to method */
302:                if (parameterTypes.length == 0) {
303:                    if ((args != null) && (args.length != 0))
304:                        throw new IllegalArgumentException(
305:                                "wrong number of arguments");
306:                } else {
307:                    if ((args == null)
308:                            || (args.length != parameterTypes.length))
309:                        throw new IllegalArgumentException(
310:                                "wrong number of arguments");
311:                }
312:
313:                CVM.setContextArtificial();
314:
315:                /* NOTE:  Consider reordering for more efficient
316:                   testing for common cases. */
317:                try {
318:                    if (returnType == Void.TYPE) {
319:                        invokeV(obj, args);
320:                    } else if (returnType == Boolean.TYPE) {
321:                        retval = new Boolean(invokeZ(obj, args));
322:                    } else if (returnType == Character.TYPE) {
323:                        retval = new Character(invokeC(obj, args));
324:                    } else if (returnType == Float.TYPE) {
325:                        retval = new Float(invokeF(obj, args));
326:                    } else if (returnType == Double.TYPE) {
327:                        retval = new Double(invokeD(obj, args));
328:                    } else if (returnType == Byte.TYPE) {
329:                        retval = new Byte(invokeB(obj, args));
330:                    } else if (returnType == Short.TYPE) {
331:                        retval = new Short(invokeS(obj, args));
332:                    } else if (returnType == Integer.TYPE) {
333:                        retval = new Integer(invokeI(obj, args));
334:                    } else if (returnType == Long.TYPE) {
335:                        retval = new Long(invokeL(obj, args));
336:                    } else {
337:                        /* Object return type */
338:                        retval = invokeA(obj, args);
339:                    }
340:                } catch (ArgumentException e) {
341:                    throw new IllegalArgumentException(
342:                            "wrong object type, or unwrapping conversion failed: "
343:                                    + e.getMessage());
344:                } catch (AccessException e) {
345:                    throw new IllegalAccessException(name);
346:                } catch (Throwable e) {
347:                    throw new InvocationTargetException(e);
348:                }
349:                return retval;
350:            }
351:
352:            private native void invokeV(Object obj, Object[] args)
353:                    throws ArgumentException, AccessException, Exception;
354:
355:            private native boolean invokeZ(Object obj, Object[] args)
356:                    throws ArgumentException, AccessException, Exception;
357:
358:            private native char invokeC(Object obj, Object[] args)
359:                    throws ArgumentException, AccessException, Exception;
360:
361:            private native float invokeF(Object obj, Object[] args)
362:                    throws ArgumentException, AccessException, Exception;
363:
364:            private native double invokeD(Object obj, Object[] args)
365:                    throws ArgumentException, AccessException, Exception;
366:
367:            private native byte invokeB(Object obj, Object[] args)
368:                    throws ArgumentException, AccessException, Exception;
369:
370:            private native short invokeS(Object obj, Object[] args)
371:                    throws ArgumentException, AccessException, Exception;
372:
373:            private native int invokeI(Object obj, Object[] args)
374:                    throws ArgumentException, AccessException, Exception;
375:
376:            private native long invokeL(Object obj, Object[] args)
377:                    throws ArgumentException, AccessException, Exception;
378:
379:            private native Object invokeA(Object obj, Object[] args)
380:                    throws ArgumentException, AccessException, Exception;
381:
382:            /*
383:             * Avoid clone()
384:             */
385:            static Class[] copy(Class[] in) {
386:                int l = in.length;
387:                if (l == 0)
388:                    return in;
389:                Class[] out = new Class[l];
390:                for (int i = 0; i < l; i++)
391:                    out[i] = in[i];
392:                return out;
393:            }
394:        }
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