001: /*
002: * Licensed to the Apache Software Foundation (ASF) under one or more
003: * contributor license agreements. See the NOTICE file distributed with
004: * this work for additional information regarding copyright ownership.
005: * The ASF licenses this file to You under the Apache License, Version 2.0
006: * (the "License"); you may not use this file except in compliance with
007: * the License. You may obtain a copy of the License at
008: *
009: * http://www.apache.org/licenses/LICENSE-2.0
010: *
011: * Unless required by applicable law or agreed to in writing, software
012: * distributed under the License is distributed on an "AS IS" BASIS,
013: * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014: * See the License for the specific language governing permissions and
015: * limitations under the License.
016: *
017: */
018: package org.apache.tools.ant.util;
019:
020: import java.lang.reflect.InvocationTargetException;
021: import java.lang.reflect.Method;
022: import org.apache.tools.ant.BuildException;
023: import java.lang.reflect.Field;
024:
025: /**
026: * Utility class to handle reflection on java objects.
027: * The class contains static methods to call reflection
028: * methods, catch any exceptions, converting them
029: * to BuildExceptions.
030: */
031:
032: public class ReflectUtil {
033:
034: /** private constructor */
035: private ReflectUtil() {
036: }
037:
038: /**
039: * Call a method on the object with no parameters.
040: * @param obj the object to invoke the method on.
041: * @param methodName the name of the method to call
042: * @return the object returned by the method
043: */
044: public static Object invoke(Object obj, String methodName) {
045: try {
046: Method method;
047: method = obj.getClass().getMethod(methodName,
048: (Class[]) null);
049: return method.invoke(obj, (Object[]) null);
050: } catch (Exception t) {
051: throwBuildException(t);
052: return null; // NotReached
053: }
054: }
055:
056: /**
057: * Call a method on the object with one argument.
058: * @param obj the object to invoke the method on.
059: * @param methodName the name of the method to call
060: * @param argType the type of argument.
061: * @param arg the value of the argument.
062: * @return the object returned by the method
063: */
064: public static Object invoke(Object obj, String methodName,
065: Class argType, Object arg) {
066: try {
067: Method method;
068: method = obj.getClass().getMethod(methodName,
069: new Class[] { argType });
070: return method.invoke(obj, new Object[] { arg });
071: } catch (Exception t) {
072: throwBuildException(t);
073: return null; // NotReached
074: }
075: }
076:
077: /**
078: * Call a method on the object with two argument.
079: * @param obj the object to invoke the method on.
080: * @param methodName the name of the method to call
081: * @param argType1 the type of the first argument.
082: * @param arg1 the value of the first argument.
083: * @param argType2 the type of the second argument.
084: * @param arg2 the value of the second argument.
085: * @return the object returned by the method
086: */
087: public static Object invoke(Object obj, String methodName,
088: Class argType1, Object arg1, Class argType2, Object arg2) {
089: try {
090: Method method;
091: method = obj.getClass().getMethod(methodName,
092: new Class[] { argType1, argType2 });
093: return method.invoke(obj, new Object[] { arg1, arg2 });
094: } catch (Exception t) {
095: throwBuildException(t);
096: return null; // NotReached
097: }
098: }
099:
100: /**
101: * Get the value of a field in an object.
102: * @param obj the object to look at.
103: * @param fieldName the name of the field in the object.
104: * @return the value of the field.
105: * @throws BuildException if there is an error.
106: */
107: public static Object getField(Object obj, String fieldName)
108: throws BuildException {
109: try {
110: Field field = obj.getClass().getDeclaredField(fieldName);
111: field.setAccessible(true);
112: return field.get(obj);
113: } catch (Exception t) {
114: throwBuildException(t);
115: return null; // NotReached
116: }
117: }
118:
119: /**
120: * A method to convert an invocationTargetException to
121: * a buildexception and throw it.
122: * @param t the invocation target exception.
123: * @throws BuildException the converted exception.
124: */
125: public static void throwBuildException(Exception t)
126: throws BuildException {
127: if (t instanceof InvocationTargetException) {
128: Throwable t2 = ((InvocationTargetException) t)
129: .getTargetException();
130: if (t2 instanceof BuildException) {
131: throw (BuildException) t2;
132: }
133: throw new BuildException(t2);
134: } else {
135: throw new BuildException(t);
136: }
137: }
138: }
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