Square’s meticulous HTTP client for Java and Kotlin.
Type-safe HTTP client for Android and Java by Square, Inc.
Feign makes writing java http clients easier
Java HTTP Request Library
Eclipse Jetty - Web Container & Clients - supports HTTP/2, HTTP/1.1, HTTP/1.0, websocket, servlets, and more
http-kit is a minimalist, event-driven, high-performance Clojure HTTP server/client library with WebSocket and asynchronous support
Unirest in Java: Simplified, lightweight HTTP client library.
Asynchronous Java made easier
Fast Parallel Async HTTP client as a Service to monitor and manage 10,000 web servers. (Java+Akka)