The Micronaut framework was introduced as an alternative to Spring Boot for building microservice applications. At first glance, it is very similar to Spring. It also implements patterns like dependency injection and inversion of control based on annotations, however, it uses JSR-330 (java.inject) to do it. It has been designed specifically for building serverless functions, Android applications, and low memory-footprint microservices. This means that it should have a faster startup time, lower memory usage, and be easier to unit test than competing frameworks. However, today I don't want to focus on those characteristics of Micronaut. I'm going to show you how to build a simple microservices-based system using this framework. You can easily compare it with Spring Boot and Spring Cloud by reading my previous article about the same subject Quick Guide to Microservices with Spring Boot 2.0, Eureka and Spring Cloud. Does Micronaut have a chance to gain the same popularity as Spring Boot? Let's find out.
Our sample system consists of three independent microservices that communicate with each other. All of them integrate with Consul in order to fetch shared configurations. After startup, every single service will register itself in Consul. The applications organization-service and department-service call endpoints exposed by other microservices using the Micronaut declarative HTTP client. The traces from communication are sent to Zipkin. The source code of the sample applications is available on GitHub in the sample-micronaut-microservices repository.