    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} implementation that handles conversion
    021 * to and from <strong>java.lang.Class</strong> 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 <em>default value</em> or throw a
    028 * <code>ConversionException</code> if a conversion error occurs.
    029 *
    030 * @since 1.4
    031 */
    032public final class ClassConverter extends AbstractConverter {
    033
    034    /**
    035     * Construct a <strong>java.lang.Class</strong> <em>Converter</em> that throws
    036     * a <code>ConversionException</code> if an error occurs.
    037     */
    038    public ClassConverter() {
    039    }
    040
    041    /**
    042     * Construct a <strong>java.lang.Class</strong> <em>Converter</em> that returns
    043     * a default value if an error occurs.
    044     *
    045     * @param defaultValue The default value to be returned
    046     * if the value to be converted is missing or an error
    047     * occurs converting the value.
    048     */
    049    public ClassConverter(final Object defaultValue) {
    050        super(defaultValue);
    051    }
    052
    053    /**
    054     * <p>Convert a java.lang.Class or object into a String.</p>
    055     *
    056     * @param value The input value to be converted
    057     * @return the converted String value.
    058     * @since 1.8.0
    059     */
    060    @Override
    061    protected String convertToString(final Object value) {
    062        return value instanceof Class ? ((Class<?>)value).getName() : value.toString();
    063    }
    064
    065    /**
    066     * <p>Convert the input object into a java.lang.Class.</p>
    067     *
    068     * @param <T> Target type of the conversion.
    069     * @param type Data type to which this value should be converted.
    070     * @param value The input value to be converted.
    071     * @return The converted value.
    072     * @throws Throwable if an error occurs converting to the specified type
    073     * @since 1.8.0
    074     */
    075    @Override
    076    protected <T> T convertToType(final Class<T> type, final Object value) throws Throwable {
    077        if (Class.class.equals(type)) {
    078            ClassLoader classLoader = Thread.currentThread()
    079                    .getContextClassLoader();
    080            if (classLoader != null) {
    081                try {
    082                    return type.cast(classLoader.loadClass(value.toString()));
    083                } catch (final ClassNotFoundException ex) {
    084                    // Don't fail, carry on and try this class's class loader
    085                    // (see issue# BEANUTILS-263)
    086                }
    087            }
    088
    089            // Try this class's class loader
    090            classLoader = ClassConverter.class.getClassLoader();
    091            return type.cast(classLoader.loadClass(value.toString()));
    092        }
    093
    094        throw conversionException(type, value);
    095    }
    096
    097    /**
    098     * Return the default type this <code>Converter</code> handles.
    099     *
    100     * @return The default type this <code>Converter</code> handles.
    101     * @since 1.8.0
    102     */
    103    @Override
    104    protected Class<?> getDefaultType() {
    105        return Class.class;
    106    }
    107
    108}