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The Core Camel Java DSL based router
/**
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.camel.processor;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import org.apache.camel.AsyncCallback;
import org.apache.camel.AsyncProcessor;
import org.apache.camel.CamelContext;
import org.apache.camel.Exchange;
import org.apache.camel.Processor;
import org.apache.camel.util.AsyncProcessorConverterHelper;
import org.apache.camel.util.AsyncProcessorHelper;
import org.apache.camel.util.ExchangeHelper;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import static org.apache.camel.processor.PipelineHelper.continueProcessing;
/**
* Creates a Pipeline pattern where the output of the previous step is sent as
* input to the next step, reusing the same message exchanges
*
* @version
*/
public class Pipeline extends MulticastProcessor {
private static final Logger LOG = LoggerFactory.getLogger(Pipeline.class);
private String id;
public Pipeline(CamelContext camelContext, Collection processors) {
super(camelContext, processors);
}
public static Processor newInstance(CamelContext camelContext, List processors) {
if (processors.isEmpty()) {
return null;
} else if (processors.size() == 1) {
return processors.get(0);
}
return new Pipeline(camelContext, processors);
}
public static Processor newInstance(final CamelContext camelContext, final Processor... processors) {
if (processors == null || processors.length == 0) {
return null;
} else if (processors.length == 1) {
return processors[0];
}
final List toBeProcessed = new ArrayList<>(processors.length);
for (Processor processor : processors) {
if (processor != null) {
toBeProcessed.add(processor);
}
}
return new Pipeline(camelContext, toBeProcessed);
}
@Override
public void process(Exchange exchange) throws Exception {
AsyncProcessorHelper.process(this, exchange);
}
@Override
public boolean process(Exchange exchange, AsyncCallback callback) {
Iterator processors = getProcessors().iterator();
Exchange nextExchange = exchange;
boolean first = true;
while (continueRouting(processors, nextExchange)) {
if (first) {
first = false;
} else {
// prepare for next run
nextExchange = createNextExchange(nextExchange);
}
// get the next processor
Processor processor = processors.next();
AsyncProcessor async = AsyncProcessorConverterHelper.convert(processor);
boolean sync = process(exchange, nextExchange, callback, processors, async);
// continue as long its being processed synchronously
if (!sync) {
LOG.trace("Processing exchangeId: {} is continued being processed asynchronously", exchange.getExchangeId());
// the remainder of the pipeline will be completed async
// so we break out now, then the callback will be invoked which then continue routing from where we left here
return false;
}
LOG.trace("Processing exchangeId: {} is continued being processed synchronously", exchange.getExchangeId());
// check for error if so we should break out
if (!continueProcessing(nextExchange, "so breaking out of pipeline", LOG)) {
break;
}
}
// logging nextExchange as it contains the exchange that might have altered the payload and since
// we are logging the completion if will be confusing if we log the original instead
// we could also consider logging the original and the nextExchange then we have *before* and *after* snapshots
LOG.trace("Processing complete for exchangeId: {} >>> {}", exchange.getExchangeId(), nextExchange);
// copy results back to the original exchange
ExchangeHelper.copyResults(exchange, nextExchange);
callback.done(true);
return true;
}
private boolean process(final Exchange original, final Exchange exchange, final AsyncCallback callback,
final Iterator processors, final AsyncProcessor asyncProcessor) {
// this does the actual processing so log at trace level
LOG.trace("Processing exchangeId: {} >>> {}", exchange.getExchangeId(), exchange);
// implement asynchronous routing logic in callback so we can have the callback being
// triggered and then continue routing where we left
boolean sync = asyncProcessor.process(exchange, new AsyncCallback() {
@Override
public void done(final boolean doneSync) {
// we only have to handle async completion of the pipeline
if (doneSync) {
return;
}
// continue processing the pipeline asynchronously
Exchange nextExchange = exchange;
while (continueRouting(processors, nextExchange)) {
AsyncProcessor processor = AsyncProcessorConverterHelper.convert(processors.next());
// check for error if so we should break out
if (!continueProcessing(nextExchange, "so breaking out of pipeline", LOG)) {
break;
}
nextExchange = createNextExchange(nextExchange);
boolean isDoneSync = process(original, nextExchange, callback, processors, processor);
if (!isDoneSync) {
LOG.trace("Processing exchangeId: {} is continued being processed asynchronously", exchange.getExchangeId());
return;
}
}
ExchangeHelper.copyResults(original, nextExchange);
LOG.trace("Processing complete for exchangeId: {} >>> {}", original.getExchangeId(), original);
callback.done(false);
}
});
return sync;
}
/**
* Strategy method to create the next exchange from the previous exchange.
*
* Remember to copy the original exchange id otherwise correlation of ids in the log is a problem
*
* @param previousExchange the previous exchange
* @return a new exchange
*/
protected Exchange createNextExchange(Exchange previousExchange) {
return PipelineHelper.createNextExchange(previousExchange);
}
protected boolean continueRouting(Iterator it, Exchange exchange) {
boolean answer = true;
Object stop = exchange.getProperty(Exchange.ROUTE_STOP);
if (stop != null) {
boolean doStop = exchange.getContext().getTypeConverter().convertTo(Boolean.class, stop);
if (doStop) {
LOG.debug("ExchangeId: {} is marked to stop routing: {}", exchange.getExchangeId(), exchange);
answer = false;
}
} else {
// continue if there are more processors to route
answer = it.hasNext();
}
LOG.trace("ExchangeId: {} should continue routing: {}", exchange.getExchangeId(), answer);
return answer;
}
@Override
public String toString() {
return "Pipeline[" + getProcessors() + "]";
}
@Override
public String getTraceLabel() {
return "pipeline";
}
@Override
public String getId() {
return id;
}
@Override
public void setId(String id) {
this.id = id;
}
}