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jsonissa / jsonista / jsoniin, jsonilla / jsonilta / jsonille
Clojure library for fast JSON encoding and decoding.
- Explicit configuration
- Uses jackson-databind
- Mostly written in Java for speed
- API docs
- FAQ
Faster than data.json or Cheshire while still having the necessary features for web development. Designed for use with Muuntaja.
Blogged:
Hi! We are Metosin, a consulting company. These libraries have evolved out of the work we do for our clients. We maintain & develop this project, for you, for free. Issues and pull requests welcome! However, if you want more help using the libraries, or want us to build something as cool for you, consider our commercial support.
Requires Java1.8+
(require '[jsonista.core :as j]) (j/write-value-as-string {"hello" 1}) ;; => "{\"hello\":1}" (j/read-value *1) ;; => {"hello" 1}
Using explicit ObjectMapper:
(-> {:dog {:name "Teppo"}} (j/write-value-as-bytes j/default-object-mapper) (j/read-value j/default-object-mapper)) ;; => {"dog" {"name" "Teppo"}}
Using keyword keys:
(-> {:dog {:name "Teppo"}} (j/write-value-as-bytes j/keyword-keys-object-mapper) (j/read-value j/keyword-keys-object-mapper)) ;; => {:dog {:name "Teppo"}}
Changing how map keys are encoded & decoded:
(defn reverse-string [s] (apply str (reverse s))) (def mapper (j/object-mapper {:encode-key-fn (comp reverse-string name) :decode-key-fn (comp keyword reverse-string)})) (-> {:kikka "kukka"} (doto prn) (j/write-value-as-string mapper) (doto prn) (j/read-value mapper) (prn)) ; {:kikka "kukka"} ; "{\"akkik\":\"kukka\"}" ; {:kikka "kukka"}
Reading & writing directly into a file:
(def file (java.io.File. "hello.json")) (j/write-value file {"hello" "world"}) (slurp file) ;; => "{\"hello\":\"world\"}" (j/read-value file) ;; => {"hello" "world"}
Adding support for joda-time Classes, used by clj-time.
;; [com.fasterxml.jackson.datatype/jackson-datatype-joda "2.9.5"] (import '[com.fasterxml.jackson.datatype.joda JodaModule]) (import '[org.joda.time LocalDate]) (def mapper (j/object-mapper {:modules [(JodaModule.)]})) (j/write-value-as-string (LocalDate. 0) mapper) ; "\"1970-01-01\""
Adding support for lossless encoding data using tagged values. This includes both reading and writing support.
(def mapper (j/object-mapper {:encode-key-fn true :decode-key-fn true :modules [(jt/module {:handlers {Keyword {:tag "!kw" :encode jt/encode-keyword :decode keyword} PersistentHashSet {:tag "!set" :encode jt/encode-collection :decode set}}})]})) (-> {:system/status #{:status/good}} (j/write-value-as-string mapper) (doto prn) (j/read-value mapper)) ; prints "{\"system/status\":[\"!set\",[[\"!kw\",\"status/good\"]]]}" ; => {:system/status #{:status/good}}
In simple perf tests, tagged JSON is much faster than EDN or Transit.
See docs/streaming.md.
- All standard encoders and decoders are written in Java
- Protocol dispatch with
read-value&write-value - Jackson
ObjectMapperis used directly - Small functions to support JVM Inlining
Measured using lein-jmh, see perf-tests for details.
➜ jsonista git:(master) ✗ lein jmh '{:file "benchmarks.edn", :type :quick, :format :table}' {:% 100.0 :eta "00:00:00"} :benchmark :name :mode :samples :score :score-error :params ----------------------------- ------- ----------- -------- ------------------ ------------ -------------- jsonista.jmh/encode-data-json :encode :throughput 5 2011809.137 ops/s 12600.809 {:size "10b"} jsonista.jmh/encode-data-json :encode :throughput 5 382677.707 ops/s 2861.142 {:size "100b"} jsonista.jmh/encode-data-json :encode :throughput 5 66403.631 ops/s 597.436 {:size "1k"} jsonista.jmh/encode-data-json :encode :throughput 5 5480.185 ops/s 58.379 {:size "10k"} jsonista.jmh/encode-data-json :encode :throughput 5 576.691 ops/s 15.682 {:size "100k"} jsonista.jmh/encode-cheshire :encode :throughput 5 996875.314 ops/s 5688.227 {:size "10b"} jsonista.jmh/encode-cheshire :encode :throughput 5 482130.613 ops/s 2685.181 {:size "100b"} jsonista.jmh/encode-cheshire :encode :throughput 5 128936.005 ops/s 879.709 {:size "1k"} jsonista.jmh/encode-cheshire :encode :throughput 5 12209.066 ops/s 94.285 {:size "10k"} jsonista.jmh/encode-cheshire :encode :throughput 5 1258.157 ops/s 12.340 {:size "100k"} jsonista.jmh/encode-jsonista :encode :throughput 5 6356105.348 ops/s 85360.100 {:size "10b"} jsonista.jmh/encode-jsonista :encode :throughput 5 2010379.039 ops/s 67648.165 {:size "100b"} jsonista.jmh/encode-jsonista :encode :throughput 5 409264.663 ops/s 3704.992 {:size "1k"} jsonista.jmh/encode-jsonista :encode :throughput 5 34527.245 ops/s 251.065 {:size "10k"} jsonista.jmh/encode-jsonista :encode :throughput 5 2934.595 ops/s 15.858 {:size "100k"} jsonista.jmh/encode-jackson :encode :throughput 5 6275467.563 ops/s 123578.482 {:size "10b"} jsonista.jmh/encode-jackson :encode :throughput 5 2092035.098 ops/s 11417.613 {:size "100b"} jsonista.jmh/encode-jackson :encode :throughput 5 408380.251 ops/s 10912.350 {:size "1k"} jsonista.jmh/encode-jackson :encode :throughput 5 31992.554 ops/s 230.781 {:size "10k"} jsonista.jmh/encode-jackson :encode :throughput 5 2887.485 ops/s 12.491 {:size "100k"} jsonista.jmh/decode-data-json :decode :throughput 5 2257552.949 ops/s 23890.443 {:size "10b"} jsonista.jmh/decode-data-json :decode :throughput 5 498261.935 ops/s 2348.572 {:size "100b"} jsonista.jmh/decode-data-json :decode :throughput 5 85191.855 ops/s 321.961 {:size "1k"} jsonista.jmh/decode-data-json :decode :throughput 5 7763.264 ops/s 250.502 {:size "10k"} jsonista.jmh/decode-data-json :decode :throughput 5 771.691 ops/s 6.559 {:size "100k"} jsonista.jmh/decode-cheshire :decode :throughput 5 1099821.870 ops/s 14796.659 {:size "10b"} jsonista.jmh/decode-cheshire :decode :throughput 5 544013.773 ops/s 4122.539 {:size "100b"} jsonista.jmh/decode-cheshire :decode :throughput 5 109517.975 ops/s 911.623 {:size "1k"} jsonista.jmh/decode-cheshire :decode :throughput 5 10017.553 ops/s 50.871 {:size "10k"} jsonista.jmh/decode-cheshire :decode :throughput 5 1014.003 ops/s 18.609 {:size "100k"} jsonista.jmh/decode-jsonista :decode :throughput 5 3476196.425 ops/s 21535.641 {:size "10b"} jsonista.jmh/decode-jsonista :decode :throughput 5 792773.466 ops/s 8209.591 {:size "100b"} jsonista.jmh/decode-jsonista :decode :throughput 5 160180.797 ops/s 554.940 {:size "1k"} jsonista.jmh/decode-jsonista :decode :throughput 5 14151.302 ops/s 107.906 {:size "10k"} jsonista.jmh/decode-jsonista :decode :throughput 5 1508.829 ops/s 5.855 {:size "100k"} jsonista.jmh/decode-jackson :decode :throughput 5 5145394.434 ops/s 84237.662 {:size "10b"} jsonista.jmh/decode-jackson :decode :throughput 5 1339393.911 ops/s 6660.176 {:size "100b"} jsonista.jmh/decode-jackson :decode :throughput 5 274465.912 ops/s 1589.614 {:size "1k"} jsonista.jmh/decode-jackson :decode :throughput 5 29607.044 ops/s 183.068 {:size "10k"} jsonista.jmh/decode-jackson :decode :throughput 5 2539.491 ops/s 17.753 {:size "100k"}
As Miikka Koskinen, @miikka, tells it on his blog:
At that time, I was working at Metosin, a Clojure agency. Tommi Reiman (@ikitommi), one of the founders and a prolific open source developer, had an idea for how to make a fast JSON library. I thought Tommi’s idea was stupid and to show him that it won’t work, I started to implement a toy version.
The idea wasn’t easy to implement and I figured I’d make something simpler first to have a baseline. The baseline was faster than Cheshire, the number one JSON library for Clojure, and we decided to ship it. Kalle Lehikoinen (@kalekale) packaged it into jsonista. Tommi’s original idea never got implemented and I don’t even remember what it was anymore!
- Update
CHANGELOG.mdand increment the version number inproject.clj - Commit and push to Github
- Create a Github release here
- Use the version number of the release for the tag name
- The Github Actions release workflow should fire and deploy a release to clojars
Copyright © 2016-2026 Metosin Oy.
Distributed under the Eclipse Public License 2.0.