Apache AsyncWeb (built on top of the Apache MINA network framework) employs non-blocking selector driven IO at the transport level, and is asynchronous thoughout - from the initial parsing of requests, right through to and including the services implemented by users.
Apache AsyncWeb breaks away from the blocking request / response architecture found in todays popular HTTP engines. This allows it to be highly scalable and capable of supporting very high throughput - even in high processing latency scenarios.
A simple API allows new asynchronous services to be created easily - and out-of-the-box Spring integration allows them to be configured simply and with great flexibility. In addition to "endpoint" HTTP services, AsyncWeb also allows configurable "chains" of behaviour - enabling "filter" like behaviour to be applied to all requests. Pluggable "resolvers" map incoming requests to their target HTTP service - and are given access to the entire incoming request - allowing the routing possibilities to be very flexible.