    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 * @since 2.0
    042 */
    043public class DisabledListDelimiterHandler extends AbstractListDelimiterHandler
    044{
    045    /**
    046     * A default instance of this class. Because it is safe to share
    047     * {@code DisabledListDelimiterHandler} objects this instance can be used
    048     * whenever such an object is needed.
    049     */
    050    public static final ListDelimiterHandler INSTANCE =
    051            new DisabledListDelimiterHandler();
    052
    053    /**
    054     * {@inheritDoc} This implementation always throws an
    055     * {@code UnsupportedOperationException} exception.
    056     */
    057    @Override
    058    public Object escapeList(final List<?> values, final ValueTransformer transformer)
    059    {
    060        throw new UnsupportedOperationException(
    061                "Escaping lists is not supported!");
    062    }
    063
    064    /**
    065     * {@inheritDoc} This implementation always returns a collection containing
    066     * the passed in string as its single element. The string is not changed,
    067     * the {@code trim} flag is ignored. (The {@code trim} flag refers to the
    068     * components extracted from the string. Because no components are extracted
    069     * nothing is trimmed.)
    070     */
    071    @Override
    072    protected Collection<String> splitString(final String s, final boolean trim)
    073    {
    074        final Collection<String> result = new ArrayList<>(1);
    075        result.add(s);
    076        return result;
    077    }
    078
    079    /**
    080     * {@inheritDoc} This implementation returns the passed in string without
    081     * any changes.
    082     */
    083    @Override
    084    protected String escapeString(final String s)
    085    {
    086        return s;
    087    }
    088}