How to pretty print JSON to a file in Clojure?

Question

I would like to store JSON content in files but using the pretty version.

Just to be clear, this is the normal JSON:

{"b":2, "a":1}

This is the pretty version of it:

{
    "b": 2,
    "a": 1
}

Is there a way in Clojure to achieve this?

Librate

The pprint function in clojure.data.json looks like what you want. I suppose you can do the write on another thread if diverting *out* is a problem. – Daunt

Answer 1

Use the cheshire library found here and use the generate-string function with the pretty flag set to true

Example

;; generate some JSON with pretty formatting
(generate-string {:foo "bar" :baz {:eggplant [1 2 3]}} {:pretty true})
;; {
;;   "foo" : "bar",
;;   "baz" : {
;;     "eggplant" : [ 1, 2, 3 ]
;;   }
;; }

Skeie

Should also consider my solution below if you don't want or need an external library. – Bahr

Answer 2

You can use the built-in with-out-str function to capture anything written to the output buffer and store it as a string.

(with-out-str (clojure.data.json/pprint your-map-or-whatever))

Bahr

Is there a way to avoid capturing to an internal string buffer and writing (or spit'ting) straight to a file? – Circumcise