Add fromJson to all API response models

[cammace]

Now that we are using AutoValue, the response objects which get created during the serialization of JSON require a type adapter factory which can often be confusing in times when you want to deserialize a JSON string into a DirectionsResponse for example. Doing so without adding the type adapter factory will result in:

Failed to invoke public com.mapbox.directions.v5.models.DirectionsRoute() with no args

To make this easier, I'm proposing we add a static factory method to all API model classes which would looks something like:

public static DirectionsResponse fromJson(String json) {
  return GsonBuilder().registerTypeAdapterFactory(DirectionsAdapterFactory.create()).create()
      .fromJson(directionsRoute, DirectionsResponse.class);
}

cc: @zugaldia

[zugaldia]

I like it. If I understand it correctly, this would bring functionality consistent with what we already provide for other types like GeoJSON (https://github.com/mapbox/mapbox-java/blob/master/mapbox/libjava-geojson/src/main/java/com/mapbox/services/commons/geojson/Feature.java#L130-L142). Correct?

[cammace]

Exactly, this is inspired by the trouble I ran into when debugging this. AutoValue Gson type adapter factory documentation for reference.

[lilykaiser]

Is this still in progress?

[jethromayuk]

This would be great.

[zugaldia]

This landed for directions models with #854.

@jethro-2018 could you share a bit more about your use case (service, serialization needed, ...)? Thanks!

[stale]

This issue has been automatically detected as stale because it has not had recent activity and will be archived. Thank you for your contributions.