    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}
    021 * implementation that converts an incoming
    022 * object into a <code>java.lang.String</code> object.
    023 * <p>
    024 * Note that ConvertUtils really is designed to do string->object conversions,
    025 * and offers very little support for object->string conversions. The
    026 * ConvertUtils/ConvertUtilsBean methods only select a converter to apply
    027 * based upon the target type being converted to, and generally assume that
    028 * the input is a string (by calling its toString method if needed).
    029 * <p>
    030 * This class is therefore just a dummy converter that converts its input
    031 * into a string by calling the input object's toString method and returning
    032 * that value.
    033 * <p>
    034 * It is possible to replace this converter with something that has a big
    035 * if/else statement that selects behaviour based on the real type of the
    036 * object being converted (or possibly has a map of converters, and looks
    037 * them up based on the class of the input object). However this is not part
    038 * of the existing ConvertUtils framework.
    039 *
    040 *
    041 * @version $Id$
    042 * @since 1.3
    043 */
    044public final class StringConverter extends AbstractConverter {
    045
    046
    047    /**
    048     * Construct a <b>java.lang.String</b> <i>Converter</i> that throws
    049     * a <code>ConversionException</code> if an error occurs.
    050     */
    051    public StringConverter() {
    052        super();
    053    }
    054
    055    /**
    056     * Construct a <b>java.lang.String</b> <i>Converter</i> that returns
    057     * a default value if an error occurs.
    058     *
    059     * @param defaultValue The default value to be returned
    060     * if the value to be converted is missing or an error
    061     * occurs converting the value.
    062     */
    063    public StringConverter(final Object defaultValue) {
    064        super(defaultValue);
    065    }
    066
    067    /**
    068     * Return the default type this <code>Converter</code> handles.
    069     *
    070     * @return The default type this <code>Converter</code> handles.
    071     * @since 1.8.0
    072     */
    073    @Override
    074    protected Class<?> getDefaultType() {
    075        return String.class;
    076    }
    077
    078    /**
    079     * Convert the specified input object into an output object of the
    080     * specified type.
    081     *
    082     * @param <T> Target type of the conversion.
    083     * @param type Data type to which this value should be converted.
    084     * @param value The input value to be converted.
    085     * @return The converted value.
    086     * @throws Throwable if an error occurs converting to the specified type
    087     * @since 1.8.0
    088     */
    089    @Override
    090    protected <T> T convertToType(final Class<T> type, final Object value) throws Throwable {
    091        // We have to support Object, too, because this class is sometimes
    092        // used for a standard to Object conversion
    093        if (String.class.equals(type) || Object.class.equals(type)) {
    094            return type.cast(value.toString());
    095        }
    096        throw conversionException(type, value);
    097    }
    098
    099
    100}