/*
* Copyright 2006-2007 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.batch.item.support;
import org.springframework.batch.item.ItemProcessor;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.util.Assert;
import java.util.List;
/**
* Composite {@link ItemProcessor} that passes the item through a sequence of
* injected <code>ItemTransformer</code>s (return value of previous
* transformation is the entry value of the next).<br>
* <br>
*
* Note the user is responsible for injecting a chain of {@link ItemProcessor}s
* that conforms to declared input and output types.
*
* @author Robert Kasanicky
*/
public class CompositeItemProcessor<I, O> implements ItemProcessor<I, O>, InitializingBean {
private List<? extends ItemProcessor<?, ?>> delegates;
@Override
@SuppressWarnings("unchecked")
public O process(I item) throws Exception {
Object result = item;
for (ItemProcessor<?, ?> delegate : delegates) {
if (result == null) {
return null;
}
result = processItem(delegate, result);
}
return (O) result;
}
/*
* Helper method to work around wildcard capture compiler error: see http://docs.oracle.com/javase/tutorial/java/generics/capture.html
* The method process(capture#1-of ?) in the type ItemProcessor<capture#1-of ?,capture#2-of ?> is not applicable for the arguments (Object)
*/
@SuppressWarnings("unchecked")
private <T> Object processItem(ItemProcessor<T, ?> processor, Object input) throws Exception {
return processor.process((T) input);
}
@Override
public void afterPropertiesSet() throws Exception {
Assert.notNull(delegates, "The 'delegates' may not be null");
Assert.notEmpty(delegates, "The 'delegates' may not be empty");
}
public void setDelegates(List<? extends ItemProcessor<?, ?>> delegates) {
this.delegates = delegates;
}
}