Microservices architecture has gained popularity in recent years due to its ability to build scalable and resilient applications. One of the key aspects of building microservices is enabling communication between services in an efficient and decoupled manner. In this blog post, we will explore how to build event-driven microservices using GlassFish and Eclipse MicroProfile Reactive Messaging in Java.

GlassFish: The Application Server for Microservices

GlassFish is an open-source Java EE application server that provides a robust and reliable platform for running microservices. It offers features such as containerization, scalability, and high availability, making it an ideal choice for building microservices applications.

Eclipse MicroProfile Reactive Messaging

MicroProfile Reactive Messaging is a specification that allows developers to build event-driven applications using microservices. It provides a set of APIs and annotations to simplify the development of reactive systems. With Reactive Messaging, you can easily connect and communicate between microservices using messaging patterns such as publish/subscribe, request/reply, and streaming.

Setting up GlassFish with Eclipse MicroProfile Reactive Messaging

To get started, make sure you have GlassFish installed on your machine. You can download the latest version from the official GlassFish website. Once installed, follow these steps:

1. Create a new Maven project in your preferred IDE.
2. Add the necessary dependencies to your project’s pom.xml file:

<dependency>
    <groupId>org.eclipse.microprofile.reactive.messaging</groupId>
    <artifactId>microprofile-reactive-messaging-api</artifactId>
    <version>1.0</version>
</dependency>

1. Create a new class for your microservice and annotate it with the @ApplicationScoped annotation:

import org.eclipse.microprofile.reactive.messaging.Incoming;
import org.eclipse.microprofile.reactive.messaging.Outgoing;

import javax.enterprise.context.ApplicationScoped;

@ApplicationScoped
public class MyMicroservice {

    @Incoming("input")
    @Outgoing("output")
    public String processMessage(String message) {
        // Process the message and return the result
        return "Processed: " + message;
    }
}

1. Configure the messaging channels in your GlassFish configuration file. For example, in glassfish-web.xml:

<glassfish-web-app>
    <resource-ref>
        <res-ref-name>jms/ConnectionFactory</res-ref-name>
        <jndi-name>java:comp/DefaultJMSConnectionFactory</jndi-name>
    </resource-ref>
</glassfish-web-app>

1. Deploy your microservice to GlassFish and start the server.

Communicating Between Microservices

With GlassFish and Reactive Messaging set up, you can now easily communicate between microservices using messaging channels. Here’s an example of sending a message from one microservice to another:

import org.eclipse.microprofile.reactive.messaging.Channel;
import org.eclipse.microprofile.reactive.messaging.Emitter;

import javax.inject.Inject;

public class MessageSender {

    @Inject
    @Channel("input")
    private Emitter<String> inputChannel;

    public void sendMessage(String message) {
        inputChannel.send(message);
    }
}

In the above example, we inject the Emitter for the desired messaging channel using the @Inject annotation. We can then use the send method to send a message to that channel.

Conclusion

Building event-driven microservices with GlassFish and Eclipse MicroProfile Reactive Messaging provides an efficient and decoupled way of communication between services. By leveraging the power of messaging patterns, developers can build scalable and resilient microservices applications. Give it a try and explore the possibilities of event-driven architectures in your Java applications.

#microservices #eventdriven #Java