/*
* 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.integration.async;
import java.util.concurrent.Callable;
import java.util.concurrent.Future;
import java.util.concurrent.FutureTask;
import org.springframework.batch.core.StepExecution;
import org.springframework.batch.core.scope.context.StepContext;
import org.springframework.batch.core.scope.context.StepSynchronizationManager;
import org.springframework.batch.item.ItemProcessor;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.core.task.SyncTaskExecutor;
import org.springframework.core.task.TaskExecutor;
import org.springframework.util.Assert;
/**
* An {@link ItemProcessor} that delegates to a nested processor and in the
* background. To allow for background processing the return value from the
* processor is a {@link Future} which needs to be unpacked before the item can
* be used by a client.
*
* @author Dave Syer
*
* @param <I> the input object type
* @param <O> the output object type (will be wrapped in a Future)
*/
public class AsyncItemProcessor<I, O> implements ItemProcessor<I, Future<O>>, InitializingBean {
private ItemProcessor<I, O> delegate;
private TaskExecutor taskExecutor = new SyncTaskExecutor();
/**
* Check mandatory properties (the {@link #setDelegate(ItemProcessor)}).
*
* @see InitializingBean#afterPropertiesSet()
*/
public void afterPropertiesSet() throws Exception {
Assert.notNull(delegate, "The delegate must be set.");
}
/**
* The {@link ItemProcessor} to use to delegate processing to in a
* background thread.
*
* @param delegate the {@link ItemProcessor} to use as a delegate
*/
public void setDelegate(ItemProcessor<I, O> delegate) {
this.delegate = delegate;
}
/**
* The {@link TaskExecutor} to use to allow the item processing to proceed
* in the background. Defaults to a {@link SyncTaskExecutor} so no threads
* are created unless this is overridden.
*
* @param taskExecutor a {@link TaskExecutor}
*/
public void setTaskExecutor(TaskExecutor taskExecutor) {
this.taskExecutor = taskExecutor;
}
/**
* Transform the input by delegating to the provided item processor. The
* return value is wrapped in a {@link Future} so that clients can unpack it
* later.
*
* @see ItemProcessor#process(Object)
*/
public Future<O> process(final I item) throws Exception {
final StepExecution stepExecution = getStepExecution();
FutureTask<O> task = new FutureTask<O>(new Callable<O>() {
public O call() throws Exception {
if (stepExecution != null) {
StepSynchronizationManager.register(stepExecution);
}
try {
return delegate.process(item);
}
finally {
if (stepExecution != null) {
StepSynchronizationManager.close();
}
}
}
});
taskExecutor.execute(task);
return task;
}
/**
* @return the current step execution if there is one
*/
private StepExecution getStepExecution() {
StepContext context = StepSynchronizationManager.getContext();
if (context==null) {
return null;
}
StepExecution stepExecution = context.getStepExecution();
return stepExecution;
}
}