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ring-jetty9-adapter (rj9a)

Ring adapter for Jetty 9 with HTTP2 and WebSocket support.

This is a simple and plain wrapper on Jetty 9. It doesn't introduce additional thread model or anything else (no unofficial ring variance, no core.async). You are free to add those on top of our base API.

As of Ring 1.6, the official Jetty adapter has been updated to Jetty 9.2. However, rj9a tracks most recent Jetty release and offers additional features like http/2 and websocket.

From 0.12, we ship conscrypt TLS implementation by default, which offers better performance and compatibility. If conscrypt is not available in your platform, you can still fallback to JDK implementation by excluding conscrypt dependencies and including OpenJDK8 or JDK9 dependencies. See example profiles in project.clj for detail.



latest version on clojars


In the REPL:

(require '[ring.adapter.jetty9 :refer [run-jetty]])
(run-jetty app {:port 50505}) ;; same as the 'official' adapter

In ns declaration:

(ns my.server
  (:require [ring.adapter.jetty9 :refer [run-jetty]]))

Ring 1.6 async handler

(require '[ring.adapter.jetty9 :refer [run-jetty]])

(defn app [request send-response raise-error]
  (send-response {:body "It works!"}))
(run-jetty app {:port 50505 :async? true})

Use HTTP 1.1 Only

If you use plain socket http 1.1 only, for example, behind an nginx with ssl off-loading, you can exclude HTTPs dependencies to reduce the uberjar size:

:exclusions [org.eclipse.jetty/jetty-alpn-conscrypt-server


To enable HTTP/2 on cleartext and secure transport, you can simply add options to run-jetty like:

(jetty/run-jetty dummy-app {:port 5000
                            :h2c? true  ;; enable cleartext http/2
                            :h2? true   ;; enable http/2
                            :ssl? true  ;; ssl is required for http/2
                            :ssl-port 5443
                            :keystore "dev-resources/keystore.jks"
                            :key-password "111111"
                            :keystore-type "jks"})


You can define following handlers for websocket events.

(def ws-handler {:on-connect (fn [ws])
                 :on-error (fn [ws e])
                 :on-close (fn [ws status-code reason])
                 :on-text (fn [ws text-message])
                 :on-bytes (fn [ws bytes offset len])})

WebSocketProtocol allows you to read and write data on the ws value:

  • (send! ws msg)
  • (send! ws msg callback)
  • (close! ws)
  • (remote-addr ws)
  • (idle-timeout! ws timeout)

Notice that we support different type of msg:

  • byte[] and ByteBuffer: send binary websocket message
  • String and other Object: send text websocket message
  • (fn [ws]) (clojure function): Custom function you can operate on Jetty's RemoteEndpoint

A callback can also be specified for send!:

(send! ws msg {:write-failed (fn [throwable]) :write-success (fn [])})

A callback is a map where keys :write-failed and :write-success are optional.

There is a new option :websockets available. Accepting a map of context path and listener class:

(use 'ring.adapter.jetty9)
(run-jetty app {:websockets {"/loc" ws-handler}})

In the javascript:

// remember to add the trailing slash.
// Otherwise, jetty will return a 302 on websocket upgrade request,
// which is not supported by most browsers.
var ws = new WebSocket("ws://somehost/loc/");
ws.onopen = ....

If you want to omit the trailing slash from your URLs (and not receive a redirect from Jetty), you can start the server like:

(run-jetty app {:websockets {"/loc" ws-handler}
                :allow-null-path-info true})

Websocket Handshake

Sometimes you may have a negotiation with the websocket client on the handshake (upgrade request) phase. You can define a ring like function that returns the websocket handler, or raises an error. You may also select a subprotocol from (:subprotocol request) and configure available (:extensions request). See websocket example for detail.


You can find examples in examples folder. To run example:

  • http: lein with-profile default,example-http run a very basic example of ring handler
  • async: lein with-profile default,example-async run ring 1.6 async handler example
  • http2: lein with-profile default,example-http2 run (NOTE that your will need OpenJDK to run this example)
  • websocket: lein with-profile default,example-websocket run



Copyright © 2013-2017 Sun Ning

Distributed under the Eclipse Public License, the same as Clojure.

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Ning Sun, Sun Ning, Thomas Crowley, Joe Littlejohn, Dmitri Sotnikov & Michael Klishin
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