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 package org.apache.commons.collections.functors; 018 019 import java.io.Serializable; 020 import java.lang.reflect.InvocationTargetException; 021 import java.lang.reflect.Method; 022 023 import org.apache.commons.collections.FunctorException; 024 import org.apache.commons.collections.Transformer; 025 026 /** 027 * Transformer implementation that creates a new object instance by reflection. 028 * 029 * @since Commons Collections 3.0 030 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $ 031 * 032 * @author Stephen Colebourne 033 */ 034 public class InvokerTransformer implements Transformer, Serializable { 035 036 /** The serial version */ 037 private static final long serialVersionUID = -8653385846894047688L; 038 039 /** The method name to call */ 040 private final String iMethodName; 041 /** The array of reflection parameter types */ 042 private final Class[] iParamTypes; 043 /** The array of reflection arguments */ 044 private final Object[] iArgs; 045 046 /** 047 * Gets an instance of this transformer calling a specific method with no arguments. 048 * 049 * @param methodName the method name to call 050 * @return an invoker transformer 051 * @since Commons Collections 3.1 052 */ 053 public static Transformer getInstance(String methodName) { 054 if (methodName == null) { 055 throw new IllegalArgumentException("The method to invoke must not be null"); 056 } 057 return new InvokerTransformer(methodName); 058 } 059 060 /** 061 * Gets an instance of this transformer calling a specific method with specific values. 062 * 063 * @param methodName the method name to call 064 * @param paramTypes the parameter types of the method 065 * @param args the arguments to pass to the method 066 * @return an invoker transformer 067 */ 068 public static Transformer getInstance(String methodName, Class[] paramTypes, Object[] args) { 069 if (methodName == null) { 070 throw new IllegalArgumentException("The method to invoke must not be null"); 071 } 072 if (((paramTypes == null) && (args != null)) 073 || ((paramTypes != null) && (args == null)) 074 || ((paramTypes != null) && (args != null) && (paramTypes.length != args.length))) { 075 throw new IllegalArgumentException("The parameter types must match the arguments"); 076 } 077 if (paramTypes == null || paramTypes.length == 0) { 078 return new InvokerTransformer(methodName); 079 } else { 080 paramTypes = (Class[]) paramTypes.clone(); 081 args = (Object[]) args.clone(); 082 return new InvokerTransformer(methodName, paramTypes, args); 083 } 084 } 085 086 /** 087 * Constructor for no arg instance. 088 * 089 * @param methodName the method to call 090 */ 091 private InvokerTransformer(String methodName) { 092 super(); 093 iMethodName = methodName; 094 iParamTypes = null; 095 iArgs = null; 096 } 097 098 /** 099 * Constructor that performs no validation. 100 * Use <code>getInstance</code> if you want that. 101 * 102 * @param methodName the method to call 103 * @param paramTypes the constructor parameter types, not cloned 104 * @param args the constructor arguments, not cloned 105 */ 106 public InvokerTransformer(String methodName, Class[] paramTypes, Object[] args) { 107 super(); 108 iMethodName = methodName; 109 iParamTypes = paramTypes; 110 iArgs = args; 111 } 112 113 /** 114 * Transforms the input to result by invoking a method on the input. 115 * 116 * @param input the input object to transform 117 * @return the transformed result, null if null input 118 */ 119 public Object transform(Object input) { 120 if (input == null) { 121 return null; 122 } 123 try { 124 Class cls = input.getClass(); 125 Method method = cls.getMethod(iMethodName, iParamTypes); 126 return method.invoke(input, iArgs); 127 128 } catch (NoSuchMethodException ex) { 129 throw new FunctorException("InvokerTransformer: The method '" + iMethodName + "' on '" + input.getClass() + "' does not exist"); 130 } catch (IllegalAccessException ex) { 131 throw new FunctorException("InvokerTransformer: The method '" + iMethodName + "' on '" + input.getClass() + "' cannot be accessed"); 132 } catch (InvocationTargetException ex) { 133 throw new FunctorException("InvokerTransformer: The method '" + iMethodName + "' on '" + input.getClass() + "' threw an exception", ex); 134 } 135 } 136 137 }