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.Constructor; 021 import java.lang.reflect.InvocationTargetException; 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 InstantiateTransformer implements Transformer, Serializable { 035 036 /** The serial version */ 037 private static final long serialVersionUID = 3786388740793356347L; 038 039 /** Singleton instance that uses the no arg constructor */ 040 public static final Transformer NO_ARG_INSTANCE = new InstantiateTransformer(); 041 042 /** The constructor parameter types */ 043 private final Class[] iParamTypes; 044 /** The constructor arguments */ 045 private final Object[] iArgs; 046 047 /** 048 * Transformer method that performs validation. 049 * 050 * @param paramTypes the constructor parameter types 051 * @param args the constructor arguments 052 * @return an instantiate transformer 053 */ 054 public static Transformer getInstance(Class[] paramTypes, Object[] args) { 055 if (((paramTypes == null) && (args != null)) 056 || ((paramTypes != null) && (args == null)) 057 || ((paramTypes != null) && (args != null) && (paramTypes.length != args.length))) { 058 throw new IllegalArgumentException("Parameter types must match the arguments"); 059 } 060 061 if (paramTypes == null || paramTypes.length == 0) { 062 return NO_ARG_INSTANCE; 063 } else { 064 paramTypes = (Class[]) paramTypes.clone(); 065 args = (Object[]) args.clone(); 066 } 067 return new InstantiateTransformer(paramTypes, args); 068 } 069 070 /** 071 * Constructor for no arg instance. 072 */ 073 private InstantiateTransformer() { 074 super(); 075 iParamTypes = null; 076 iArgs = null; 077 } 078 079 /** 080 * Constructor that performs no validation. 081 * Use <code>getInstance</code> if you want that. 082 * 083 * @param paramTypes the constructor parameter types, not cloned 084 * @param args the constructor arguments, not cloned 085 */ 086 public InstantiateTransformer(Class[] paramTypes, Object[] args) { 087 super(); 088 iParamTypes = paramTypes; 089 iArgs = args; 090 } 091 092 /** 093 * Transforms the input Class object to a result by instantiation. 094 * 095 * @param input the input object to transform 096 * @return the transformed result 097 */ 098 public Object transform(Object input) { 099 try { 100 if (input instanceof Class == false) { 101 throw new FunctorException( 102 "InstantiateTransformer: Input object was not an instanceof Class, it was a " 103 + (input == null ? "null object" : input.getClass().getName())); 104 } 105 Constructor con = ((Class) input).getConstructor(iParamTypes); 106 return con.newInstance(iArgs); 107 108 } catch (NoSuchMethodException ex) { 109 throw new FunctorException("InstantiateTransformer: The constructor must exist and be public "); 110 } catch (InstantiationException ex) { 111 throw new FunctorException("InstantiateTransformer: InstantiationException", ex); 112 } catch (IllegalAccessException ex) { 113 throw new FunctorException("InstantiateTransformer: Constructor must be public", ex); 114 } catch (InvocationTargetException ex) { 115 throw new FunctorException("InstantiateTransformer: Constructor threw an exception", ex); 116 } 117 } 118 119 }