Ratpack is a set of Java libraries that facilitate fast, efficient, evolvable and well tested HTTP applications.
It is built on the highly performant and efficient Netty event-driven networking engine.
Ratpack focuses on allowing HTTP applications to be efficient, modular, adaptive to new requirements and technologies, and well-tested over time.
The core of Ratpack is made up of only Java 8, Netty, Google Guava and Reactive Streams.
You can write Ratpack applications in Java 8 or any alternative JVM language that plays well with Java. Specific support for the Groovy language is provided, utilizing the latest static compilation and typing features.
Ratpack does not take a heavily opinionated approach as to what libraries and tools you should use to compose your application. As the developer of the application, you are in control. Direct integration of tools and libraries is favored over generic abstractions.
Ratpack is for nontrivial, high performance, low resource usage, HTTP applications.