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 */
017package org.apache.commons.beanutils.converters;
018
019/**
020 * {@link org.apache.commons.beanutils.Converter} implementaion that handles conversion
021 * to and from <b>java.lang.Class</b> objects.
022 * <p>
023 * The class will be loaded from the thread context class
024 * loader (if it exists); otherwise the class loader that loaded this class
025 * will be used.
026 * <p>
027 * Can be configured to either return a <i>default value</i> or throw a
028 * <code>ConversionException</code> if a conversion error occurs.
029 *
030 * @author Tomas Viberg
031 * @version $Revision: 690380 $ $Date: 2008-08-29 21:04:38 +0100 (Fri, 29 Aug 2008) $
032 * @since 1.4
033 */
034public final class ClassConverter extends AbstractConverter {
035
036    /**
037     * Construct a <b>java.lang.Class</b> <i>Converter</i> that throws
038     * a <code>ConversionException</code> if an error occurs.
039     */
040    public ClassConverter() {
041        super();
042    }
043
044    /**
045     * Construct a <b>java.lang.Class</b> <i>Converter</i> that returns
046     * a default value if an error occurs.
047     *
048     * @param defaultValue The default value to be returned
049     * if the value to be converted is missing or an error
050     * occurs converting the value.
051     */
052    public ClassConverter(Object defaultValue) {
053        super(defaultValue);
054    }
055
056    /**
057     * Return the default type this <code>Converter</code> handles.
058     *
059     * @return The default type this <code>Converter</code> handles.
060     * @since 1.8.0
061     */
062    protected Class getDefaultType() {
063        return Class.class;
064    }
065
066    /**
067     * <p>Convert a java.lang.Class or object into a String.</p>
068     *
069     * @param value The input value to be converted
070     * @return the converted String value.
071     * @since 1.8.0
072     */
073    protected String convertToString(Object value) {
074        return (value instanceof Class) ? ((Class)value).getName() : value.toString();
075    }
076
077    /**
078     * <p>Convert the input object into a java.lang.Class.</p>
079     *
080     * @param type Data type to which this value should be converted.
081     * @param value The input value to be converted.
082     * @return The converted value.
083     * @throws Throwable if an error occurs converting to the specified type
084     * @since 1.8.0
085     */
086    protected Object convertToType(Class type, Object value) throws Throwable {
087        ClassLoader classLoader =
088            Thread.currentThread().getContextClassLoader();
089        if (classLoader != null) {
090            try {
091                return (classLoader.loadClass(value.toString()));
092            } catch (ClassNotFoundException ex) {
093                // Don't fail, carry on and try this class's class loader
094                // (see issue# BEANUTILS-263)
095            }
096        }
097
098        // Try this class's class loader
099        classLoader = ClassConverter.class.getClassLoader();
100        return (classLoader.loadClass(value.toString()));
101    }
102
103}