(require '[cognitect.transit :as transit])
(import [java.io ByteArrayInputStream ByteArrayOutputStream])

;; Write data to a stream
(def out (ByteArrayOutputStream. 4096))
(def writer (transit/writer out :json))
(transit/write writer "foo")
(transit/write writer {:a [1 2]})

;; Take a peek at the JSON
(.toString out)
;; => "{\"~#'\":\"foo\"} [\"^ \",\"~:a\",[1,2]]"

;; Read data from a stream
(def in (ByteArrayInputStream. (.toByteArray out)))
(def reader (transit/reader in :json))
(prn (transit/read reader))  ;; => "foo"
(prn (transit/read reader))  ;; => {:a [1 2]}