    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.Iterator;
    022
    023/**
    024 * <p>
    025 * An abstract base class for concrete {@code ListDelimiterHandler} implementations.
    026 * </p>
    027 * <p>
    028 * This base class provides a fully functional implementation for parsing a value object which can deal with different
    029 * cases like collections, arrays, iterators, etc. This logic is typically needed by every concrete subclass. Other
    030 * methods are partly implemented handling special corner cases like <b>null</b> values; concrete subclasses do not have
    031 * do implement the corresponding checks.
    032 * </p>
    033 *
    034 * @since 2.0
    035 */
    036public abstract class AbstractListDelimiterHandler implements ListDelimiterHandler {
    037
    038    /**
    039     * Flattens the given iterator. For each element in the iteration {@code flatten()} is called recursively.
    040     *
    041     * @param handler the working handler
    042     * @param target the target collection
    043     * @param iterator the iterator to process
    044     * @param limit a limit for the number of elements to extract
    045     */
    046    static void flattenIterator(final ListDelimiterHandler handler, final Collection<Object> target, final Iterator<?> iterator, final int limit) {
    047        int size = target.size();
    048        while (size < limit && iterator.hasNext()) {
    049            target.addAll(handler.flatten(iterator.next(), limit - size));
    050            size = target.size();
    051        }
    052    }
    053
    054    /**
    055     * {@inheritDoc} This implementation checks whether the object to be escaped is a string. If yes, it delegates to
    056     * {@link #escapeString(String)}, otherwise no escaping is performed. Eventually, the passed in transformer is invoked
    057     * so that additional encoding can be performed.
    058     */
    059    @Override
    060    public Object escape(final Object value, final ValueTransformer transformer) {
    061        return transformer.transformValue(value instanceof String ? escapeString((String) value) : value);
    062    }
    063
    064    /**
    065     * Escapes the specified string. This method is called by {@code escape()} if the passed in object is a string. Concrete
    066     * subclasses have to implement their specific escaping logic here, so that the list delimiters they support are
    067     * properly escaped.
    068     *
    069     * @param s the string to be escaped (not <b>null</b>)
    070     * @return the escaped string
    071     */
    072    protected abstract String escapeString(String s);
    073
    074    /**
    075     * Performs the actual work as advertised by the {@code parse()} method. This method delegates to
    076     * {@link #flatten(Object, int)} without specifying a limit.
    077     *
    078     * @param value the value to be processed
    079     * @return a &quot;flat&quot; collection containing all primitive values of the passed in object
    080     */
    081    private Collection<?> flatten(final Object value) {
    082        return flatten(value, Integer.MAX_VALUE);
    083    }
    084
    085    /**
    086     * {@inheritDoc} Depending on the type of the passed in object the following things happen:
    087     * <ul>
    088     * <li>Strings are checked for delimiter characters and split if necessary. This is done by calling the {@code split()}
    089     * method.</li>
    090     * <li>For objects implementing the {@code Iterable} interface, the corresponding {@code Iterator} is obtained, and
    091     * contained elements are added to the resulting iteration.</li>
    092     * <li>Arrays are treated as {@code Iterable} objects.</li>
    093     * <li>All other types are directly inserted.</li>
    094     * <li>Recursive combinations are supported, e.g. a collection containing an array that contains strings: The resulting
    095     * collection will only contain primitive objects.</li>
    096     * </ul>
    097     */
    098    @Override
    099    public Iterable<?> parse(final Object value) {
    100        return flatten(value);
    101    }
    102
    103    /**
    104     * {@inheritDoc} This implementation handles the case that the passed in string is <b>null</b>. In this case, an empty
    105     * collection is returned. Otherwise, this method delegates to {@link #splitString(String, boolean)}.
    106     */
    107    @Override
    108    public Collection<String> split(final String s, final boolean trim) {
    109        return s == null ? new ArrayList<>(0) : splitString(s, trim);
    110    }
    111
    112    /**
    113     * Actually splits the passed in string which is guaranteed to be not <b>null</b>. This method is called by the base
    114     * implementation of the {@code split()} method. Here the actual splitting logic has to be implemented.
    115     *
    116     * @param s the string to be split (not <b>null</b>)
    117     * @param trim a flag whether the single components have to be trimmed
    118     * @return a collection with the extracted components of the passed in string
    119     */
    120    protected abstract Collection<String> splitString(String s, boolean trim);
    121}