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.Factory; 024 import org.apache.commons.collections.FunctorException; 025 026 /** 027 * Factory 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 InstantiateFactory implements Factory, Serializable { 035 036 /** The serial version */ 037 private static final long serialVersionUID = -7732226881069447957L; 038 039 /** The class to create */ 040 private final Class iClassToInstantiate; 041 /** The constructor parameter types */ 042 private final Class[] iParamTypes; 043 /** The constructor arguments */ 044 private final Object[] iArgs; 045 /** The constructor */ 046 private transient Constructor iConstructor = null; 047 048 /** 049 * Factory method that performs validation. 050 * 051 * @param classToInstantiate the class to instantiate, not null 052 * @param paramTypes the constructor parameter types 053 * @param args the constructor arguments 054 * @return a new instantiate factory 055 */ 056 public static Factory getInstance(Class classToInstantiate, Class[] paramTypes, Object[] args) { 057 if (classToInstantiate == null) { 058 throw new IllegalArgumentException("Class to instantiate must not be null"); 059 } 060 if (((paramTypes == null) && (args != null)) 061 || ((paramTypes != null) && (args == null)) 062 || ((paramTypes != null) && (args != null) && (paramTypes.length != args.length))) { 063 throw new IllegalArgumentException("Parameter types must match the arguments"); 064 } 065 066 if (paramTypes == null || paramTypes.length == 0) { 067 return new InstantiateFactory(classToInstantiate); 068 } else { 069 paramTypes = (Class[]) paramTypes.clone(); 070 args = (Object[]) args.clone(); 071 return new InstantiateFactory(classToInstantiate, paramTypes, args); 072 } 073 } 074 075 /** 076 * Constructor that performs no validation. 077 * Use <code>getInstance</code> if you want that. 078 * 079 * @param classToInstantiate the class to instantiate 080 */ 081 public InstantiateFactory(Class classToInstantiate) { 082 super(); 083 iClassToInstantiate = classToInstantiate; 084 iParamTypes = null; 085 iArgs = null; 086 findConstructor(); 087 } 088 089 /** 090 * Constructor that performs no validation. 091 * Use <code>getInstance</code> if you want that. 092 * 093 * @param classToInstantiate the class to instantiate 094 * @param paramTypes the constructor parameter types, not cloned 095 * @param args the constructor arguments, not cloned 096 */ 097 public InstantiateFactory(Class classToInstantiate, Class[] paramTypes, Object[] args) { 098 super(); 099 iClassToInstantiate = classToInstantiate; 100 iParamTypes = paramTypes; 101 iArgs = args; 102 findConstructor(); 103 } 104 105 /** 106 * Find the Constructor for the class specified. 107 */ 108 private void findConstructor() { 109 try { 110 iConstructor = iClassToInstantiate.getConstructor(iParamTypes); 111 112 } catch (NoSuchMethodException ex) { 113 throw new IllegalArgumentException("InstantiateFactory: The constructor must exist and be public "); 114 } 115 } 116 117 /** 118 * Creates an object using the stored constructor. 119 * 120 * @return the new object 121 */ 122 public Object create() { 123 // needed for post-serialization 124 if (iConstructor == null) { 125 findConstructor(); 126 } 127 128 try { 129 return iConstructor.newInstance(iArgs); 130 131 } catch (InstantiationException ex) { 132 throw new FunctorException("InstantiateFactory: InstantiationException", ex); 133 } catch (IllegalAccessException ex) { 134 throw new FunctorException("InstantiateFactory: Constructor must be public", ex); 135 } catch (InvocationTargetException ex) { 136 throw new FunctorException("InstantiateFactory: Constructor threw an exception", ex); 137 } 138 } 139 140 }