Spring Boot tutorial
Spring Boot is an open source Java-based framework for developing sites, web applications and micro services.
You can use java or some jvm languages like Kotlin, Groovy or Scala.
It is increases productivity and avoids writing lots boilerplate code. Because most tasks already solved by Spring Boot itself or by libraries of the Spring Boot ecosystem. As example, it has emeded tomcat http server, generate crud repository in couple lines. It has default configurations for some databases, template engines and etc.
It provides lots of plugins to develop and test applications.