karavan-demo/aggregator/Aggregator.java

import org.apache.camel.BindToRegistry;
import org.apache.camel.Exchange;
import org.apache.camel.Processor;
import org.apache.camel.Exchange;
import org.apache.camel.AggregationStrategy;
import java.util.ArrayList;

@BindToRegistry("aggregator")
public class Aggregator implements AggregationStrategy {

    public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
        if (oldExchange == null) {
            return newExchange;
        }

        String oldBody = oldExchange.getIn().getBody(String.class);
        String newBody = newExchange.getIn().getBody(String.class);
        oldExchange.getIn().setBody(oldBody + "+" + newBody);
        return oldExchange;
    }
}