Carefully examining the preceding RESTful service will reveal whether this really constitutes a microservice. At first glance, the preceding RESTful service is a fully qualified interoperable REST/JSON service. However, it is not fully autonomous in nature. This is primarily because the service relies on an underlying application server or web container. In the preceding example, a war was explicitly created and deployed on a Tomcat server.
This is a traditional approach to developing RESTful services as a web application. However, from the microservices point of view, one needs a mechanism to develop services as executables, self-contained JAR files with an embedded HTTP listener.
Spring Boot is a tool that allows easy development of such kinds of services. Dropwizard and WildFly Swarm are alternate server-less RESTful stacks.