    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 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}