How to use Aggregator EIP using Spring and Apache Camel?

Jasvinder S Saggu

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Jul 9, 2021

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pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.4.7</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.jss</groupId>
    <artifactId>camel</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>camel</name>
    <description>Apache Camel with Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <junit.platform.version>1.6.0</junit.platform.version>
        <camel.version>3.7.3</camel.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.apache.camel.springboot</groupId>
            <artifactId>camel-spring-boot-starter</artifactId>
            <version>${camel.version}</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
     </dependencies>
  </project>

AggregatorRoute.java

package com.jss.camel.components.routes.aggregation;

import org.apache.camel.LoggingLevel;
import org.apache.camel.Message;
import org.apache.camel.builder.RouteBuilder;
import org.springframework.stereotype.Component;

import java.util.Date;
import java.util.Random;

@Component
public class AggregatorRoute extends RouteBuilder {
    final String CORRELATION_ID = "correlationId";

    @Override
    public void configure() throws Exception {

        Random random = new Random();

        from("timer:insurance?period=200")
                .process(exchange ->
                {
                    Message message = exchange.getMessage();
                    message.setHeader(CORRELATION_ID, random.nextInt(4));
                    message.setBody(new Date() + "");
                })
                .aggregate(header(CORRELATION_ID), new MyAggregationStrategy())
                .completionSize(5)
                .log(LoggingLevel.ERROR, "${header." + CORRELATION_ID + "} ${body}")
        ;
    }
}

MyAggregationStrategy.java

package com.jss.camel.components.routes.aggregation;

import org.apache.camel.Exchange;

import java.util.Objects;

public class MyAggregationStrategy implements org.apache.camel.AggregationStrategy {
    @Override
    public Exchange aggregate(Exchange oldExchange, Exchange newExchange) {
        if (Objects.isNull(oldExchange)) {
            return newExchange;
        }

        String oldBody = oldExchange.getIn().getBody(String.class);
        String newBody = newExchange.getIn().getBody(String.class);

        String aggBody = oldBody + "->" + newBody;

        oldExchange.getIn().setBody(aggBody);

        return oldExchange;
    }
}