Javalin

Create asynchronous client and server applications. Anything from microservices to multiplatform HTTP client apps in a simple way. Open Source, free, and fun! Ktor is built from the ground up using Kotlin and Coroutines. You get to use a concise, multiplatform language, as well as the power of asynchronous programming with an intuitive imperative flow. Ktor allows you to use only what you need, and to structure your application the way you need it. In addition, you can also extend Ktor with your own plugin very easily. Brought to you by JetBrains, creators of IntelliJ IDEA, Kotlin, and more. Ktor is not only used by our customers but also internally at JetBrains. In addition, you have top-notch tooling support!

Jetty provides a web server and servlet container, additionally providing support for HTTP/2, WebSocket, OSGi, JMX, JNDI, JAAS and many other integrations. These components are open source and are freely available for commercial use and distribution. Jetty is used in a wide variety of projects and products, both in development and production. Jetty has long been loved by developers due to its long history of being easily embedded in devices, tools, frameworks, application servers, and modern cloud services. Full-featured and standards-based. Open source and commercially usable, flexible and extensible, small footprint, embeddable, asynchronous, enterprise scalable, and dual-licensed under Apache and Eclipse. Large clusters, such as Facebook Presto. Cloud computing, such as Google AppEngine. With the direction of Java and the JakartaEE project (formerly JavaEE) in 2020, the current recommended version of Jetty for use depends upon the servlet API version, desired licensing, etc.