# What is Moleculer Java?

Moleculer Java (or Moleculer for Java) is the implementation of the Moleculer Microservices Framework for the JVM. Moleculer Ecosystem is designed to facilitate the development of non-blocking distributed applications. Moleculer is useful for a large range of applications: micro-services, REST backends for modern JavaScript front-ends, high volume message processing, common platform for modules written in different languages.

# Features

  • Polyglot (implemented in multiple languages)
  • High-performance, non-blocking messaging and event APIs
  • Asynchronous REST Services for high-load React, Angular or VueJS applications
  • Runs as a standard J2EE application or with a built-in Netty server
  • Fault Tolerance and high availability (circuit breaker, request timeout, retry, etc.)
  • Load balanced requests & events (round-robin, random, cpu-usage, network latency, sharding)
  • Pluggable transporters (P2P TCP, NATS, MQTT, Redis, AMQP, Kafka, JMS, Ably.io)
  • Pluggable serializers (JSON, MessagePack, BSON, CBOR, Ion, Smile)
  • Built-in caching solution (memory cache, Redis cache, off-heap cache, JCache)
  • Send and receive streamed data (for transferring large files, media content)
  • Built-in service registry & dynamic service discovery
  • Supports WebSockets, SSL, Middlewares (for using cache, encryption or logging modules)
  • Supports template engines for generating server-side HTMLs (FreeMarker, Jade, Thymeleaf, etc.)
  • Interactive developer console (local or telnet) with custom commands
  • Open source - Moleculer is 100% open source and free of charge

# Prerequisites

Moleculer Java requires Java 8.

# REST service example

Here's how to create a REST service using Moleculer:

import services.moleculer.ServiceBroker;
import services.moleculer.service.Action;
import services.moleculer.service.Service;
import services.moleculer.web.ApiGateway;
import services.moleculer.web.netty.NettyServer;

public class Sample {
  public static void main(String[] args) throws Exception {
    new ServiceBroker()
      .createService(new NettyServer(8080))
      .createService(new ApiGateway("**"))
      .createService(new Service("math") {
        Action add = ctx -> {
          return ctx.params.get("a", 0) +
                 ctx.params.get("b", 0);

After starting the program, enter the following URL into your browser:

The response will be "9" (because 3 and 6 are the values of the "a" and "b" parameters). The above service can also be invoked using a POST method. To do this, submit the {"a":3,"b":5} JSON (as POST body) to this URL:

# Dependencies of the example

The Moleculer packages can be downloaded from the central Maven repository.


dependencies {
    implementation group: 'org.slf4j',          name: 'slf4j-jdk14',        version: '1.7.30'
    implementation group: 'com.github.berkesa', name: 'moleculer-java',     version: '1.2.17'
    implementation group: 'com.github.berkesa', name: 'moleculer-java-web', version: '1.3.2' 



# Detailed Example

This demo project demonstrating the basic capabilities of a Moleculer-based web application. The project can be imported into the Eclipse IDE or IntelliJ IDEA. The brief examples illustrate the following:

  • Integration of Moleculer API into the Spring Boot Framework
  • Configuring HTTP Routes and Middlewares
  • Creating non-blocking Moleculer Services
  • Publishing and invoking Moleculer Services as REST Services
  • Generating HTML pages in multiple languages using Template Engines
  • Using WebSockets (sending real-time server-side events to browsers)
  • Using file upload and download
  • Video streaming and server-side image generation
  • Creating a WAR from the finished project (Servlet-based runtime)
  • Run code without any changes in "standalone mode" (Netty-based runtime)

# Subprojects



Node.js-based Moleculer Services can be used in Java-based applications as well as local Services (in order for Node.js and Java Moleculer applications to communicate with each other, they must both configure a Transporter of the same type).

# License

Moleculer for Java is available under the MIT license, can be used in commercial products for free.