001/*
002 * Copyright 2014 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 org.springframework.batch.item.ItemProcessor;
020import org.springframework.classify.Classifier;
021import org.springframework.classify.ClassifierSupport;
022
023/**
024 * Calls one of a collection of ItemProcessors, based on a router
025 * pattern implemented through the provided {@link Classifier}.
026 * 
027 * Note the user is responsible for injecting a {@link Classifier}
028 * that returns an ItemProcessor that conforms to the declared input and output types.
029 * 
030 * @author Jimmy Praet
031 * @since 3.0
032 */
033public class ClassifierCompositeItemProcessor<I,O> implements ItemProcessor<I, O> {
034
035        private Classifier<? super I, ItemProcessor<?, ? extends O>> classifier = 
036                        new ClassifierSupport<I, ItemProcessor<?, ? extends O>> (null);
037
038        /**
039         * Establishes the classifier that will determine which {@link ItemProcessor} to use.
040         * @param classifier the {@link Classifier} to set
041         */
042        public void setClassifier(Classifier<? super I, ItemProcessor<?, ? extends O>> classifier) {
043                this.classifier = classifier;
044        }
045        
046        /**
047         * Delegates to injected {@link ItemProcessor} instances according to the
048         * classification by the {@link Classifier}.
049         */
050        @Override
051        public O process(I item) throws Exception {
052                return processItem(classifier.classify(item), item);
053        }
054        
055    /* 
056     * Helper method to work around wildcard capture compiler error: see https://docs.oracle.com/javase/tutorial/java/generics/capture.html
057     * The method process(capture#4-of ?) in the type ItemProcessor<capture#4-of ?,capture#5-of ? extends O> is not applicable for the arguments (I)
058     */
059    @SuppressWarnings("unchecked")
060        private <T> O processItem(ItemProcessor<T, ? extends O> processor, I input) throws Exception {
061        return processor.process((T) input);
062    }   
063
064}