Writing JSON custom types in responses

[wm.ma...@gmail.com]

Hi,

I have a web-service implemented with Liberator that returns various data from a postgres database via JDBC.

I see that Liberator very helpfully automatically serialises my maps of data from the database result-sets to JSON.

This works just fine in most cases without me having to do anything.

However, I have some complex types like java.sql.Timestamp or java.util.Date that fail to get serialised.

java.lang.Exception: Don't know how to write JSON of class java.util.Date

            json.clj:367 clojure.data.json/write-generic

That's fair enough, it needs to be told how I want those classes serialised...

So with clojue.data.json, I believe there is a mechanism using :value-fn to serialise such types, but how do I plug in to Liberator to do that? Or is there something else I should be looking at?

Thanks!

Regards,

-M.

[Philipp Meier]

Hi,

Am Sonntag, 15. Dezember 2013 13:42:54 UTC+1 schrieb wm.ma...@gmail.com:

However, I have some complex types like java.sql.Timestamp or java.util.Date that fail to get serialised.

java.lang.Exception: Don't know how to write JSON of class java.util.Date

            json.clj:367 clojure.data.json/write-generic

That's fair enough, it needs to be told how I want those classes serialised...

So with clojue.data.json, I believe there is a mechanism using :value-fn to serialise such types, but how do I plug in to Liberator to do that? Or is there something else I should be looking at?

At the moment there is no way when you depend on liberator's automatic response generation. But you can do the following:

(defresource foo

  :handle-ok (fn [{{mt :media-type} :representation}]

                (if (= "application/json" mt)

                    (core.data.json/write-str my-data :value-fm my-value-fm)

                    (as-response my-data)))

;; my-data is the data structure you return from the handler right

;; my-value-fm is the function that serializes Date to a string

-billy.

 

[Paolo Piersanti]

this works too
(defmethod render-map-generic "application/json"
  [data context]
  (json/write-str data :value-fn (fn [key value] (if (instance? java.sql.Timestamp value) (str value)))))

Paolo