001/*
002 * Copyright 2006-2007 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.batch.item.file.transform;
018
019import java.util.Collection;
020
021
022/**
023 * An implementation of {@link LineAggregator} that concatenates a collection of
024 * items of a common type with the system line separator.
025 * 
026 * @author Dave Syer
027 * 
028 */
029public class RecursiveCollectionLineAggregator<T> implements LineAggregator<Collection<T>> {
030
031        private static final String LINE_SEPARATOR = System.getProperty("line.separator");
032
033        private LineAggregator<T> delegate = new PassThroughLineAggregator<>();
034
035        /**
036         * Public setter for the {@link LineAggregator} to use on single items, that
037         * are not Strings. This can be used to strategise the conversion of
038         * collection and array elements to a String.<br>
039         * 
040         * @param delegate the line aggregator to set. Defaults to a pass through.
041         */
042        public void setDelegate(LineAggregator<T> delegate) {
043                this.delegate = delegate;
044        }
045
046        /*
047         * (non-Javadoc)
048         * @see org.springframework.batch.item.file.transform.LineAggregator#aggregate(java.lang.Object)
049         */
050        @Override
051        public String aggregate(Collection<T> items) {
052                StringBuilder builder = new StringBuilder();
053                for (T value : items) {
054                        builder.append(delegate.aggregate(value)).append(LINE_SEPARATOR);
055                }
056                return builder.delete(builder.length() - LINE_SEPARATOR.length(), builder.length()).toString();
057        }
058
059}