MyEndAggregationStrategy.java

package camelinaction;

import org.apache.camel.Exchange;
import org.apache.camel.processor.aggregate.AggregationStrategy;

/**
 * This is the aggregation strategy which is java code for <i>aggregating</i>
 * incoming messages with the existing aggregated message. In other words
 * you use this strategy to <i>merge</i> the messages together.
 */
public class MyEndAggregationStrategy implements AggregationStrategy {

    /**
     * Aggregates the messages.
     *
     * @param oldExchange  the existing aggregated message. Is <tt>null</tt> the
     *                     very first time as there are no existing message.
     * @param newExchange  the incoming message. This is never <tt>null</tt>.
     * @return the aggregated message.
     */
    public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
        // the first time there are no existing message and therefore
        // the oldExchange is null. In these cases we just return
        // the newExchange
        if (oldExchange == null) {
            return newExchange;
        }

        // now we have both an existing message (oldExchange)
        // and a incoming message (newExchange)
        // we want to merge together.

        // in this example we add their bodies
        String oldBody = oldExchange.getIn().getBody(String.class);
        String newBody = newExchange.getIn().getBody(String.class);

        // if its the END message then do not aggregate
        if ("END".equals(newBody)) {
            return oldExchange;
        }

        // the body should be the two bodies added together
        String body = oldBody + newBody;

        // update the existing message with the added body
        oldExchange.getIn().setBody(body);
        // and return it
        return oldExchange;
    }

}