write-value closes the object

[helins]

Writing to an object in a streaming fashion is a typical use case and since Jsonista aims for performance, supporting that is rather expected. As opposed to using write-value-as-string or write-value-as-bytes and then copying the result to an object like a writer.

Currently, this is not possible since write-value closes the given object, hence an exception is thrown. Or maybe is it Jackson itself?

I realized this while trying to write a line-delimited JSON file.

(with-open [out (clojure.java.io/writer "/tmp/foo.json")]
    (json/write-value out [:a])
    (.write out (int \newline))
    (json/write-value out [:b]))

[FiV0]

Workaround for now (credit @jarohen)

(do
  (let [obj-mapper (doto (jsonista.core/object-mapper)
                     (.disable (into-array com.fasterxml.jackson.core.JsonGenerator$Feature [com.fasterxml.jackson.core.JsonGenerator$Feature/AUTO_CLOSE_TARGET])))]
    (with-open [out (io/output-stream "/tmp/foo.json")
                wrt (io/writer out)]
      (jsonista.core/write-value wrt {"foo" 1} obj-mapper)
      (.write wrt "\n")
      (jsonista.core/write-value wrt {"bar" 1} obj-mapper)))
  (slurp "/tmp/foo.json"))

[jarohen]

Could add it into the cond-> when you build up the mapper in j/object-mapper?

(:close-targets? options) (doto (-> .getFactory (.disable JsonGenerator$Feature/AUTO_CLOSE_TARGET)))

(Happy to raise a PR or have you guys add it in, whatever's easier for you 🙂)

[opqdonut]

There is now a :close option. See docstrings and docs/streaming.md.