Undertow is a flexible performant web server written in java, providing both blocking and non-blocking API’s based on NIO.
Undertow has a composition based architecture that allows you to build a web server by combining small single purpose handlers. The gives you the flexibility to choose between a full Java EE servlet 3.1 container, or a low level non-blocking handler, to anything in between.
Undertow is designed to be fully embeddable, with easy to use fluent builder APIs.Undertow’s lifecycle is completely controlled by the embedding application.
Undertow is sponsored by JBoss and is the default web server in the Wildfly Application Server.