    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.beanutils2;
    019
    020import java.lang.reflect.InvocationTargetException;
    021import java.util.function.Function;
    022
    023import org.apache.commons.logging.Log;
    024import org.apache.commons.logging.LogFactory;
    025
    026/**
    027 * <p>
    028 * {@code Transformer} that outputs a property value.
    029 * </p>
    030 *
    031 * <p>
    032 * An implementation of {@link java.util.function.Function} that transforms the object provided by returning the value of a specified property of the object.
    033 * The constructor for {@code BeanToPropertyValueTransformer} requires the name of the property that will be used in the transformation. The property can be a
    034 * simple, nested, indexed, or mapped property as defined by {@code org.apache.commons.beanutils2.PropertyUtils}. If any object in the property path specified
    035 * by {@code propertyName</code> is <code>null} then the
    036 * outcome is based on the value of the {@code ignoreNull} 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 * }</pre>
    049 *
    050 * <p>
    051 * This would take a {@code Collection</code> of person objects and return a <code>Collection} of objects which represents the cities in which each person
    052 * lived. Assuming...
    053 * <ul>
    054 * <li>The top level object in the {@code peopleCollection} is an object which represents a person.</li>
    055 * <li>The person object has a {@code getAddress()} method which returns an object which represents a person's address.</li>
    056 * <li>The address object has a {@code getCity()} method which returns an object which represents the city in which a person lives.</li>
    057 * </ul>
    058 *
    059 * @param <T> the type of the input to the function
    060 * @param <R> the type of the result of the function
    061 * @see org.apache.commons.beanutils2.PropertyUtils
    062 * @see java.util.function.Function
    063 */
    064public class BeanToPropertyValueTransformer<T, R> implements Function<T, R> {
    065
    066    /** For logging. Each subclass gets its own log instance. */
    067    private final Log log = LogFactory.getLog(this.getClass());
    068
    069    /** The name of the property that will be used in the transformation of the object. */
    070    private final String propertyName;
    071
    072    /**
    073     * <p>
    074     * Should null objects on the property path throw an {@code IllegalArgumentException}?
    075     * </p>
    076     * <p>
    077     * Determines whether {@code null} objects in the property path will generate an
    078     * {@code IllegalArgumentException</code> or not. If set to <code>true} then if any objects
    079     * in the property path evaluate to {@code null} then the
    080     * {@code IllegalArgumentException</code> throw by <code>PropertyUtils} will be logged but
    081     * not re-thrown and {@code null</code> will be returned.  If set to <code>false} then if any
    082     * objects in the property path evaluate to {@code null} then the
    083     * {@code IllegalArgumentException</code> throw by <code>PropertyUtils} will be logged and re-thrown.
    084     * </p>
    085     */
    086    private final boolean ignoreNull;
    087
    088    /**
    089     * Constructs a Transformer which does not ignore nulls. Constructor which takes the name of the property that will be used in the transformation and
    090     * assumes {@code ignoreNull</code> to be <code>false}.
    091     *
    092     * @param propertyName The name of the property that will be used in the transformation.
    093     * @throws IllegalArgumentException If the {@code propertyName</code> is <code>null} or empty.
    094     */
    095    public BeanToPropertyValueTransformer(final String propertyName) {
    096        this(propertyName, false);
    097    }
    098
    099    /**
    100     * Constructs a Transformer and sets ignoreNull. Constructor which takes the name of the property that will be used in the transformation and a boolean
    101     * which determines whether {@code null} objects in the property path will generate an {@code IllegalArgumentException} or not.
    102     *
    103     * @param propertyName The name of the property that will be used in the transformation.
    104     * @param ignoreNull   Determines whether {@code null} objects in the property path will generate an {@code IllegalArgumentException} or not.
    105     * @throws IllegalArgumentException If the {@code propertyName</code> is <code>null} or empty.
    106     */
    107    public BeanToPropertyValueTransformer(final String propertyName, final boolean ignoreNull) {
    108        if (propertyName == null || propertyName.isEmpty()) {
    109            throw new IllegalArgumentException("propertyName cannot be null or empty");
    110        }
    111        this.propertyName = propertyName;
    112        this.ignoreNull = ignoreNull;
    113    }
    114
    115    /**
    116     * Returns the value of the property named in the transformer's constructor for the object provided. If any object in the property path leading up to the
    117     * target property is {@code null</code> then the outcome will be based on the value of the <code>ignoreNull}
    118     * attribute. By default, {@code ignoreNull</code> is <code>false} and would result in an
    119     * {@code IllegalArgumentException} if an object in the property path leading up to the
    120     * target property is {@code null}.
    121     *
    122     * &#64;param object The object to be transformed.
    123     * &#64;return The value of the property named in the transformer's constructor for the object
    124     * provided.
    125     * @throws IllegalArgumentException If an IllegalAccessException, InvocationTargetException, or
    126     * NoSuchMethodException is thrown when trying to access the property specified on the object
    127     * provided. Or if an object in the property path provided is {@code null} and
    128     * {@code ignoreNull</code> is set to <code>false}.
    129     */
    130    @Override
    131    public R apply(final T object) {
    132        R propertyValue = null;
    133        try {
    134            propertyValue = (R) PropertyUtils.getProperty(object, propertyName);
    135        } catch (final IllegalArgumentException e) {
    136            final String errorMsg = "Problem during transformation. Null value encountered in property path...";
    137            if (!ignoreNull) {
    138                throw new IllegalArgumentException(errorMsg, e);
    139            }
    140            log.warn(errorMsg, e);
    141        } catch (final IllegalAccessException e) {
    142            final String errorMsg = "Unable to access the property provided.";
    143            throw new IllegalArgumentException(errorMsg, e);
    144        } catch (final InvocationTargetException e) {
    145            final String errorMsg = "Exception occurred in property's getter";
    146            throw new IllegalArgumentException(errorMsg, e);
    147        } catch (final NoSuchMethodException e) {
    148            final String errorMsg = "No property found for name [" + propertyName + "]";
    149            throw new IllegalArgumentException(errorMsg, e);
    150        }
    151
    152        return propertyValue;
    153    }
    154
    155    /**
    156     * Returns the name of the property that will be used in the transformation of the bean.
    157     *
    158     * @return The name of the property that will be used in the transformation of the bean.
    159     */
    160    public String getPropertyName() {
    161        return propertyName;
    162    }
    163
    164    /**
    165     * Returns the flag which determines whether {@code null} objects in the property path will generate an
    166     * {@code IllegalArgumentException</code> or not. If set to <code>true} then
    167     * if any objects in the property path evaluate to {@code null} then the
    168     * {@code IllegalArgumentException</code> throw by <code>PropertyUtils} will be logged but
    169     * not re-thrown and {@code null</code> will be returned.  If set to <code>false} then if any
    170     * objects in the property path evaluate to {@code null} then the
    171     * {@code IllegalArgumentException</code> throw by <code>PropertyUtils} will be logged and re-thrown.
    172     *
    173     * @return The flag which determines whether {@code null} objects in the property path will generate an {@code IllegalArgumentException} or not.
    174     */
    175    public boolean isIgnoreNull() {
    176        return ignoreNull;
    177    }
    178}