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 018package org.apache.commons.beanutils; 019 020import org.apache.commons.collections.Transformer; 021import org.apache.commons.logging.Log; 022import org.apache.commons.logging.LogFactory; 023 024import java.lang.reflect.InvocationTargetException; 025 026 027/** 028 * <p><code>Transformer</code> that outputs a property value.</p> 029 * 030 * <p>An implementation of <code>org.apache.commons.collections.Transformer</code> that transforms 031 * the object provided by returning the value of a specified property of the object. The 032 * constructor for <code>BeanToPropertyValueTransformer</code> requires the name of the property 033 * that will be used in the transformation. The property can be a simple, nested, indexed, or 034 * mapped property as defined by <code>org.apache.commons.beanutils.PropertyUtils</code>. If any 035 * object in the property path specified by <code>propertyName</code> is <code>null</code> then the 036 * outcome is based on the value of the <code>ignoreNull</code> attribute. 037 * </p> 038 * 039 * <p> 040 * A typical usage might look like: 041 * </p> 042 * <pre><code> 043 * // create the transformer 044 * BeanToPropertyValueTransformer transformer = new BeanToPropertyValueTransformer( "person.address.city" ); 045 * 046 * // transform the Collection 047 * Collection peoplesCities = CollectionUtils.collect( peopleCollection, transformer ); 048 * </code></pre> 049 * 050 * <p> 051 * This would take a <code>Collection</code> of person objects and return a <code>Collection</code> 052 * of objects which represents the cities in which each person lived. Assuming... 053 * <ul> 054 * <li> 055 * The top level object in the <code>peeopleCollection</code> is an object which represents a 056 * person. 057 * </li> 058 * <li> 059 * The person object has a <code>getAddress()</code> method which returns an object which 060 * represents a person's address. 061 * </li> 062 * <li> 063 * The address object has a <code>getCity()</code> method which returns an object which 064 * represents the city in which a person lives. 065 * </li> 066 * </ul> 067 * 068 * @version $Id$ 069 * @see org.apache.commons.beanutils.PropertyUtils 070 * @see org.apache.commons.collections.Transformer 071 */ 072public class BeanToPropertyValueTransformer implements Transformer { 073 074 /** For logging. */ 075 private final Log log = LogFactory.getLog(this.getClass()); 076 077 /** The name of the property that will be used in the transformation of the object. */ 078 private String propertyName; 079 080 /** 081 * <p>Should null objects on the property path throw an <code>IllegalArgumentException</code>?</p> 082 * <p> 083 * Determines whether <code>null</code> objects in the property path will genenerate an 084 * <code>IllegalArgumentException</code> or not. If set to <code>true</code> then if any objects 085 * in the property path evaluate to <code>null</code> then the 086 * <code>IllegalArgumentException</code> throw by <code>PropertyUtils</code> will be logged but 087 * not rethrown and <code>null</code> will be returned. If set to <code>false</code> then if any 088 * objects in the property path evaluate to <code>null</code> then the 089 * <code>IllegalArgumentException</code> throw by <code>PropertyUtils</code> will be logged and 090 * rethrown. 091 * </p> 092 */ 093 private boolean ignoreNull; 094 095 /** 096 * Constructs a Transformer which does not ignore nulls. 097 * Constructor which takes the name of the property that will be used in the transformation and 098 * assumes <code>ignoreNull</code> to be <code>false</code>. 099 * 100 * @param propertyName The name of the property that will be used in the transformation. 101 * @throws IllegalArgumentException If the <code>propertyName</code> is <code>null</code> or 102 * empty. 103 */ 104 public BeanToPropertyValueTransformer(final String propertyName) { 105 this(propertyName, false); 106 } 107 108 /** 109 * Constructs a Transformer and sets ignoreNull. 110 * Constructor which takes the name of the property that will be used in the transformation and 111 * a boolean which determines whether <code>null</code> objects in the property path will 112 * genenerate an <code>IllegalArgumentException</code> or not. 113 * 114 * @param propertyName The name of the property that will be used in the transformation. 115 * @param ignoreNull Determines whether <code>null</code> objects in the property path will 116 * genenerate an <code>IllegalArgumentException</code> or not. 117 * @throws IllegalArgumentException If the <code>propertyName</code> is <code>null</code> or 118 * empty. 119 */ 120 public BeanToPropertyValueTransformer(final String propertyName, final boolean ignoreNull) { 121 super(); 122 123 if ((propertyName != null) && (propertyName.length() > 0)) { 124 this.propertyName = propertyName; 125 this.ignoreNull = ignoreNull; 126 } else { 127 throw new IllegalArgumentException( 128 "propertyName cannot be null or empty"); 129 } 130 } 131 132 /** 133 * Returns the value of the property named in the transformer's constructor for 134 * the object provided. If any object in the property path leading up to the target property is 135 * <code>null</code> then the outcome will be based on the value of the <code>ignoreNull</code> 136 * attribute. By default, <code>ignoreNull</code> is <code>false</code> and would result in an 137 * <code>IllegalArgumentException</code> if an object in the property path leading up to the 138 * target property is <code>null</code>. 139 * 140 * @param object The object to be transformed. 141 * @return The value of the property named in the transformer's constructor for the object 142 * provided. 143 * @throws IllegalArgumentException If an IllegalAccessException, InvocationTargetException, or 144 * NoSuchMethodException is thrown when trying to access the property specified on the object 145 * provided. Or if an object in the property path provided is <code>null</code> and 146 * <code>ignoreNull</code> is set to <code>false</code>. 147 */ 148 public Object transform(final Object object) { 149 150 Object propertyValue = null; 151 152 try { 153 propertyValue = PropertyUtils.getProperty(object, propertyName); 154 } catch (final IllegalArgumentException e) { 155 final String errorMsg = "Problem during transformation. Null value encountered in property path..."; 156 157 if (ignoreNull) { 158 log.warn("WARNING: " + errorMsg + e); 159 } else { 160 final IllegalArgumentException iae = new IllegalArgumentException(errorMsg); 161 if (!BeanUtils.initCause(iae, e)) { 162 log.error(errorMsg, e); 163 } 164 throw iae; 165 } 166 } catch (final IllegalAccessException e) { 167 final String errorMsg = "Unable to access the property provided."; 168 final IllegalArgumentException iae = new IllegalArgumentException(errorMsg); 169 if (!BeanUtils.initCause(iae, e)) { 170 log.error(errorMsg, e); 171 } 172 throw iae; 173 } catch (final InvocationTargetException e) { 174 final String errorMsg = "Exception occurred in property's getter"; 175 final IllegalArgumentException iae = new IllegalArgumentException(errorMsg); 176 if (!BeanUtils.initCause(iae, e)) { 177 log.error(errorMsg, e); 178 } 179 throw iae; 180 } catch (final NoSuchMethodException e) { 181 final String errorMsg = "No property found for name [" + 182 propertyName + "]"; 183 final IllegalArgumentException iae = new IllegalArgumentException(errorMsg); 184 if (!BeanUtils.initCause(iae, e)) { 185 log.error(errorMsg, e); 186 } 187 throw iae; 188 } 189 190 return propertyValue; 191 } 192 193 /** 194 * Returns the name of the property that will be used in the transformation of the bean. 195 * 196 * @return The name of the property that will be used in the transformation of the bean. 197 */ 198 public String getPropertyName() { 199 return propertyName; 200 } 201 202 /** 203 * Returns the flag which determines whether <code>null</code> objects in the property path will 204 * genenerate an <code>IllegalArgumentException</code> or not. If set to <code>true</code> then 205 * if any objects in the property path evaluate to <code>null</code> then the 206 * <code>IllegalArgumentException</code> throw by <code>PropertyUtils</code> will be logged but 207 * not rethrown and <code>null</code> will be returned. If set to <code>false</code> then if any 208 * objects in the property path evaluate to <code>null</code> then the 209 * <code>IllegalArgumentException</code> throw by <code>PropertyUtils</code> will be logged and 210 * rethrown. 211 * 212 * @return The flag which determines whether <code>null</code> objects in the property path will 213 * genenerate an <code>IllegalArgumentException</code> or not. 214 */ 215 public boolean isIgnoreNull() { 216 return ignoreNull; 217 } 218}