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74 lines
2.1 KiB
Markdown
74 lines
2.1 KiB
Markdown
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# Format Negotiation
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`reitit` uses [muuntaja](https://github.com/metosin/muuntaja) as a library to handle format negotiation, encoding and decoding.
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In order to have access to the options below, you need the following namespaces:
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```clj
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(require '[muuntaja.core :as m])
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```
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Then, a `muuntaja` instance must be installed in the router to your coercion benefit from the customizations.
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```clj
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(ring/ring-handler
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(ring/router
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;; your route definitions
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;; ....
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:data {:coercion reitit.coercion.spec/coercion
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:muuntaja m/instance}})
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```
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## Changing default parameters
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The current JSON formatter used by `reitit` already have the option to parse keys as `keyword` which is a sane default in Clojure. However, if you would like to parse all the `double` as `bigdecimal` you'd need to change an option of the [JSON formatter](https://github.com/metosin/jsonista)
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```clj
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(def new-muuntaja-instance
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(m/create
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(assoc-in
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m/default-options
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[:formats "application/json" :decoder-opts :bigdecimals]
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true)))
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```
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Now you should change the `m/instance` installed in the router with the `new-muuntaja-instance`.
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You can find more options for [JSON](https://cljdoc.org/d/metosin/jsonista/0.2.5/api/jsonista.core#object-mapper) and [EDN].
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## Adding custom encoder
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The example below is from `muuntaja` explaining how to add a custom encoder to parse a `java.util.Date` instance.
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```clj
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(def muuntaja-instance
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(m/create
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(assoc-in
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m/default-options
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[:formats "application/json" :encoder-opts]
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{:date-format "yyyy-MM-dd"})))
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(->> {:value (java.util.Date.)}
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(m/encode m "application/json")
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slurp)
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; => "{\"value\":\"2019-10-15\"}"
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```
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## Adding all together
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If you inspect `m/default-options` it's only a map, therefore you can compose your new muuntaja instance with as many options as you need it.
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```clj
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(def new-muuntaja
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(m/create
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(-> m/default-options
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(assoc-in [:formats "application/json" :decoder-opts :bigdecimals] true)
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(assoc-in [:formats "application/json" :encoder-opts :data-format] "yyyy-MM-dd"))))
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```
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