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.configuration2.convert;
018
019import java.util.ArrayList;
020import java.util.Collection;
021import java.util.List;
022
023/**
024 * <p>
025 * A specialized implementation of the {@code ListDelimiterHandler} interface
026 * which disables list splitting.
027 * </p>
028 * <p>
029 * This class does not recognize any list delimiters; passed in strings are
030 * returned unchanged. Also the {@code escape()} method is a dummy - there is no
031 * need for escaping delimiter characters as none are supported. Note that the
032 * method for escaping a list throws an {@code UnsupportedOperationException}.
033 * If list delimiters are not supported, there is no point in squashing multiple
034 * values into a single one.
035 * </p>
036 * <p>
037 * Implementation note: An instance of this class can be shared between multiple
038 * configuration objects. It is state-less and thread-safe.
039 * </p>
040 *
041 * @version $Id: DisabledListDelimiterHandler.java 1842194 2018-09-27 22:24:23Z ggregory $
042 * @since 2.0
043 */
044public class DisabledListDelimiterHandler extends AbstractListDelimiterHandler
045{
046    /**
047     * A default instance of this class. Because it is safe to share
048     * {@code DisabledListDelimiterHandler} objects this instance can be used
049     * whenever such an object is needed.
050     */
051    public static final ListDelimiterHandler INSTANCE =
052            new DisabledListDelimiterHandler();
053
054    /**
055     * {@inheritDoc} This implementation always throws an
056     * {@code UnsupportedOperationException} exception.
057     */
058    @Override
059    public Object escapeList(final List<?> values, final ValueTransformer transformer)
060    {
061        throw new UnsupportedOperationException(
062                "Escaping lists is not supported!");
063    }
064
065    /**
066     * {@inheritDoc} This implementation always returns a collection containing
067     * the passed in string as its single element. The string is not changed,
068     * the {@code trim} flag is ignored. (The {@code trim} flag refers to the
069     * components extracted from the string. Because no components are extracted
070     * nothing is trimmed.)
071     */
072    @Override
073    protected Collection<String> splitString(final String s, final boolean trim)
074    {
075        final Collection<String> result = new ArrayList<>(1);
076        result.add(s);
077        return result;
078    }
079
080    /**
081     * {@inheritDoc} This implementation returns the passed in string without
082     * any changes.
083     */
084    @Override
085    protected String escapeString(final String s)
086    {
087        return s;
088    }
089}