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deserializer.clj
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deserializer.clj
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(ns gregor.details.deserializer
(:require [cheshire.core :as json]
[clojure.edn :as edn])
(:import (org.apache.kafka.common.serialization Deserializer
StringDeserializer)))
(defn reify-deserializer
"Creates an implementation of the `Deserializer` protocol provided by Kafka, only implementing `deserialize`"
[deserialization-fn]
(reify
Deserializer
(close [_])
(configure [_ config is-key?])
(deserialize [_ topic payload]
(deserialization-fn topic payload))))
(defn edn-deserializer
"Create EDN deserializer"
[]
(reify-deserializer (fn [_ #^"[B" payload]
(when payload
(edn/read-string (String. payload "UTF-8"))))))
(defn json-deserializer
"Create JSON deserializer"
[]
(reify-deserializer (fn [_ #^"[B" payload]
(when payload
(json/parse-string (String. payload "UTF-8") true)))))
(defn keyword-deserializer
"Creates a String deserializer which turns the result into a keyword"
[]
(reify-deserializer (fn [_ #^"[B" payload]
(when payload
(keyword (String. payload "UTF-8"))))))
(defn string-deserializer
"Create an instance of Kafka's own StringDeserializer object"
[]
(StringDeserializer.))
(def deserializers {:edn edn-deserializer
:json json-deserializer
:keyword keyword-deserializer
:string string-deserializer})
(defn ^Deserializer ->deserializer
"Map symbolic keyword to an actual deserializer"
[deserializer-id]
(if-let [deserializer-creator (deserializers deserializer-id)]
(deserializer-creator)
(throw (ex-info "unknown deserializer" {:deserializer deserializer-id}))))