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.commons.beanutils;
019
020 import org.apache.commons.collections.Transformer;
021 import org.apache.commons.logging.Log;
022 import org.apache.commons.logging.LogFactory;
023
024 import 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 * <code><pre>
042 * // create the transformer
043 * BeanToPropertyValueTransformer transformer = new BeanToPropertyValueTransformer( "person.address.city" );
044 *
045 * // transform the Collection
046 * Collection peoplesCities = CollectionUtils.collect( peopleCollection, transformer );
047 * </pre></code>
048 * </p>
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 * @author Norm Deane
069 * @see org.apache.commons.beanutils.PropertyUtils
070 * @see org.apache.commons.collections.Transformer
071 */
072 public 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(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(String propertyName, 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(Object object) {
149
150 Object propertyValue = null;
151
152 try {
153 propertyValue = PropertyUtils.getProperty(object, propertyName);
154 } catch (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 IllegalArgumentException iae = new IllegalArgumentException(errorMsg);
161 if (!BeanUtils.initCause(iae, e)) {
162 log.error(errorMsg, e);
163 }
164 throw iae;
165 }
166 } catch (IllegalAccessException e) {
167 final String errorMsg = "Unable to access the property provided.";
168 IllegalArgumentException iae = new IllegalArgumentException(errorMsg);
169 if (!BeanUtils.initCause(iae, e)) {
170 log.error(errorMsg, e);
171 }
172 throw iae;
173 } catch (InvocationTargetException e) {
174 final String errorMsg = "Exception occurred in property's getter";
175 IllegalArgumentException iae = new IllegalArgumentException(errorMsg);
176 if (!BeanUtils.initCause(iae, e)) {
177 log.error(errorMsg, e);
178 }
179 throw iae;
180 } catch (NoSuchMethodException e) {
181 final String errorMsg = "No property found for name [" +
182 propertyName + "]";
183 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 }