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