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.support;
018
019import java.util.ArrayList;
020import java.util.LinkedHashMap;
021import java.util.List;
022import java.util.Map;
023
024import org.springframework.classify.Classifier;
025import org.springframework.classify.ClassifierSupport;
026import org.springframework.batch.item.ItemWriter;
027import org.springframework.util.Assert;
028
029/**
030 * Calls one of a collection of ItemWriters for each item, based on a router
031 * pattern implemented through the provided {@link Classifier}.
032 * 
033 * The implementation is thread-safe if all delegates are thread-safe.
034 * 
035 * @author Dave Syer
036 * @author Glenn Renfro
037 * @since 2.0
038 */
039public class ClassifierCompositeItemWriter<T> implements ItemWriter<T> {
040
041        private Classifier<T, ItemWriter<? super T>> classifier = new ClassifierSupport<T, ItemWriter<? super T>>(null);
042
043        /**
044         * @param classifier the classifier to set
045         */
046        public void setClassifier(Classifier<T, ItemWriter<? super T>> classifier) {
047                Assert.notNull(classifier, "A classifier is required.");
048                this.classifier = classifier;
049        }
050
051        /**
052         * Delegates to injected {@link ItemWriter} instances according to their
053         * classification by the {@link Classifier}.
054         */
055    @Override
056        public void write(List<? extends T> items) throws Exception {
057
058                Map<ItemWriter<? super T>, List<T>> map = new LinkedHashMap<ItemWriter<? super T>, List<T>>();
059
060                for (T item : items) {
061                        ItemWriter<? super T> key = classifier.classify(item);
062                        if (!map.containsKey(key)) {
063                                map.put(key, new ArrayList<T>());
064                        }
065                        map.get(key).add(item);
066                }
067
068                for (ItemWriter<? super T> writer : map.keySet()) {
069                        writer.write(map.get(writer));
070                }
071
072        }
073
074}