From the specification itself:
If you’ve ever argued with your team about the way your JSON responses should be formatted, JSON API can be your anti-bikeshedding tool.
By following shared conventions, you can increase productivity, take advantage of generalized tooling, and focus on what matters: your application.
Clients built around JSON API are able to take advantage of its features around efficiently caching responses, sometimes eliminating network requests entirely.
All in all, API discoverability and other HATEOAS principles make JSON-API an attractive resource serialization option.
Find the specification here
Let's start with an example User record:
data User = User
{ userId :: Int
, userFirstName :: String
, userLastName :: String
} deriving (Eq, Show)
$(deriveJSON defaultOptions ''User)
From this, we can use the json-api
package to produce a payload conformant
to the JSON-API specification like so:
-- Builds the Document which will be serialized as our
-- web server's response payload
mkDocument :: User -> Links -> Document User Text Int
mkDocument usr links =
Document
(Singleton $ toResource usr)
(Just links)
Nothing
-- Helper function to convert a User into a resource object
-- This could be our canonical serialization function for a User in any
-- response payload
toResource :: User -> Resource User Text
toResource user =
Resource resourceId resourceType user resourceLinks resourceMetaData
where
resourceId = ResourceId . pack . show . userId $ user
resourceType = ResourceType "User"
resourceLinks = Just $ userLinks user
resourceMetaData = Nothing
-- helper function to build links for a User resource
userLinks :: User -> Links
userLinks user = toLinks [ ("self", selfLink) ]
where
selfLink = toURL selfPath
selfPath = "/users/" <> (show $ userId user)
When delivered as a response from a web server, for example, we get a payload that looks like this:
{
"data":{
"attributes":{
"userFirstName":"Isaac",
"userLastName":"Newton",
"userId":1
},
"id":"1",
"meta":null,
"type":"User",
"links":{
"self":"/users/1"
}
},
"meta":null,
"links":{
"self":"/users/1"
}
}
Neat! We can see that if we would like the full User data for the User with
ID=1, we can query /users/1
. Discoverability!
We can also see from the top-level links
data that this particular payload originated
from /users/1
.
This is a very simple example to provide an introduction to the basic idea behind JSON-API and how to use this library. Check out these examples for more robust representations of resourceful payloads. Here, you'll start to see the more comprehensive benefits of a discoverable API.
There is an example project illustrating how the library can be used in the context of a web server.
Module documentation can be found on Hackage