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    package 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: 640131 $ $Date: 2008-03-23 02:10:31 +0000 (Sun, 23 Mar 2008) $
032     * @since 1.4
033     */
034    public 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         */
061        protected Class getDefaultType() {
062            return Class.class;
063        }
064    
065        /**
066         * <p>Convert a java.lang.Class or object into a String.</p>
067         *
068         * @param value The input value to be converted
069         * @return the converted String value.
070         */
071        protected String convertToString(Object value) {
072            return (value instanceof Class) ? ((Class)value).getName() : value.toString();
073        }
074    
075        /**
076         * <p>Convert the input object into a java.lang.Class.</p>
077         *
078         * @param type Data type to which this value should be converted.
079         * @param value The input value to be converted.
080         * @return The converted value.
081         * @throws Throwable if an error occurs converting to the specified type
082         */
083        protected Object convertToType(Class type, Object value) throws Throwable {
084            ClassLoader classLoader =
085                Thread.currentThread().getContextClassLoader();
086            if (classLoader != null) {
087                try {
088                    return (classLoader.loadClass(value.toString()));
089                } catch (ClassNotFoundException ex) {
090                    // Don't fail, carry on and try this class's class loader
091                    // (see issue# BEANUTILS-263)
092                }
093            }
094    
095            // Try this class's class loader
096            classLoader = ClassConverter.class.getClassLoader();
097            return (classLoader.loadClass(value.toString()));
098        }
099    
100    }