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/*
* ============LICENSE_START=========================================================
* dcae-analytics
* ================================================================================
* Copyright © 2017 AT&T Intellectual Property. All rights reserved.
* ================================================================================
* 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.
* ============LICENSE_END=========================================================
*/
package org.openecomp.dcae.analytics.common.utils;
import org.openecomp.dcae.analytics.common.exception.MessageProcessingException;
import org.openecomp.dcae.analytics.common.service.processor.MessageProcessor;
import org.openecomp.dcae.analytics.common.service.processor.ProcessorContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.Iterator;
/**
* Contains utility methods for {@link MessageProcessor}
*
* @author Rajiv Singla. Creation Date: 11/8/2016.
*/
public abstract class MessageProcessorUtils {
private static final Logger LOG = LoggerFactory.getLogger(MessageProcessorUtils.class);
/**
* Provides an abstraction how to apply {@link ProcessorContext} to next {@link MessageProcessor}
* in the message processor chain
*
* @param <P> Sub classes of Processor Context
*/
public interface MessageProcessorFunction<P extends ProcessorContext> {
/**
* Method which provides accumulated {@link ProcessorContext} from previous processors and a reference
* to next processor in the chain
*
* @param p accumulated {@link ProcessorContext} from previous processors
* @param m current {@link MessageProcessor} in the chain
* @param <M> Message processor sub classes
*
* @return processing context after computing the current Message Processor
*/
<M extends MessageProcessor<P>> P apply(P p, M m);
}
/**
* Provides an abstraction to compute a chain of {@link MessageProcessor}
*
* @param messageProcessors An iterable containing one or more {@link MessageProcessor}s
* @param initialProcessorContext An initial processing Context
* @param messageProcessorFunction messageProcessor Function
* @param <P> Sub classes for Processor Context
*
* @return processing context which results after computing the whole chain
*/
public static <P extends ProcessorContext> P computeMessageProcessorChain(
final Iterable<? extends MessageProcessor<P>> messageProcessors,
final P initialProcessorContext,
final MessageProcessorFunction<P> messageProcessorFunction) {
// Get message processor iterator
final Iterator<? extends MessageProcessor<P>> processorIterator = messageProcessors.iterator();
// If no next message processor - return initial processor context
if (!processorIterator.hasNext()) {
return initialProcessorContext;
}
// An accumulator for processor Context
P processorContextAccumulator = initialProcessorContext;
while (processorIterator.hasNext()) {
final MessageProcessor<P> nextProcessor = processorIterator.next();
// If Initial Processor Context is null
if (processorContextAccumulator == null) {
final String errorMessage =
String.format("Processor Context must not be null for Message Process: %s",
nextProcessor.getProcessorInfo().getProcessorName());
throw new MessageProcessingException(errorMessage, LOG, new IllegalStateException(errorMessage));
}
if (!processorContextAccumulator.canProcessingContinue()) {
LOG.debug("Triggering Early Termination, before Message Processor: {}, Incoming Message: {}",
nextProcessor.getProcessorInfo().getProcessorName(), processorContextAccumulator.getMessage());
break;
}
processorContextAccumulator = messageProcessorFunction.apply(processorContextAccumulator, nextProcessor);
}
return processorContextAccumulator;
}
}
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