Spring integration: Asynchronous gateways

By returning a Future or ListenableFuture from gateway method, we can make the gateway method asynchronous.

 

Step 1: Define gateway with ListenableFuture as return type.

@MessagingGateway
public interface CustomGateway {

	@Gateway(requestChannel = "printChannel")
	public ListenableFuture<String> sendToPrintChannel(String message);

}

 

Step 2: Use callback method to capture the asynchronous response.

ListenableFuture<String> reply = customGateway.sendToPrintChannel("Msg " + i);

reply.addCallback(new ListenableFutureCallback<String>() {

	@Override
	public void onSuccess(String result) {
		System.out.println(result);
	}

	@Override
	public void onFailure(Throwable ex) {
		ex.printStackTrace();
	}
});

 

Find the below working application.

 

Step 1: Create new maven project ‘asynchronous-gateway-demo’.

 

Step 2: Update pom.xml with maven dependencies.

 

pom.xml

 

<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>
	<groupId>com.sample.app</groupId>
	<artifactId>asynchronous-gateway-demo</artifactId>
	<version>1</version>

	<!-- https://mvnrepository.com/artifact/org.springframework.boot/spring-boot-starter-parent -->
	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.4.0</version>
	</parent>

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

	</dependencies>

</project>

Step 3: Define service activator.

 

PrintService.java

package com.sample.app.service;

import java.util.Random;
import java.util.concurrent.TimeUnit;

import org.springframework.integration.annotation.ServiceActivator;
import org.springframework.messaging.Message;
import org.springframework.stereotype.Component;

@Component
public class PrintService {

	@ServiceActivator(inputChannel = "printChannel")
	public String consumeStringMessage(Message<String> message) throws InterruptedException {
		
		Random random = new Random();
		int timeToSleep = random.nextInt(10);
		
		TimeUnit.SECONDS.sleep(timeToSleep);
		
		System.out.println("Received message from printChannel : " + message.getPayload());		
		return "Message " + message.getPayload() + " received";
	}
	

}

Step 4: Define gateway.

 

CustomGateway.java

package com.sample.app.gateway;

import org.springframework.integration.annotation.Gateway;
import org.springframework.integration.annotation.MessagingGateway;
import org.springframework.util.concurrent.ListenableFuture;

@MessagingGateway
public interface CustomGateway {

	@Gateway(requestChannel = "printChannel")
	public ListenableFuture<String> sendToPrintChannel(String message);

}

 

Step 5: Define main application class.

 

App.java

 

package com.sample.app;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.util.concurrent.ListenableFuture;
import org.springframework.util.concurrent.ListenableFutureCallback;

import com.sample.app.gateway.CustomGateway;

@SpringBootApplication
@Configuration
public class App {

	@Autowired
	private CustomGateway customGateway;

	public static void main(String[] args) {
		SpringApplication.run(App.class, args);
	}

	@Bean
	public CommandLineRunner demo() {
		return (args) -> {

			for (int i = 0; i < 5; i++) {
				ListenableFuture<String> reply = customGateway.sendToPrintChannel("Msg " + i);

				reply.addCallback(new ListenableFutureCallback<String>() {

					@Override
					public void onSuccess(String result) {
						System.out.println(result);
					}

					@Override
					public void onFailure(Throwable ex) {
						ex.printStackTrace();
					}
				});
			}

		};

	};

}

 

Total project structure looks like below.

 

 

Run App.java, you will see below kind of messages in console.

 

Received message from printChannel : Msg 1
Message Msg 1 received
Received message from printChannel : Msg 4
Message Msg 4 received
Received message from printChannel : Msg 0
Message Msg 0 received
Received message from printChannel : Msg 2
Message Msg 2 received
Received message from printChannel : Msg 3
Message Msg 3 received

 

You can download complete working application from below link.

https://github.com/harikrishna553/springboot/tree/master/spring-integration/asynchronous-gateway-demo

 

 

 

 

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