Spray.io REST service - Json Serialization, De-serialization - Lesson 3

View the lessons list at https://github.com/karthik20522/SprayLearning

For a REST based interface, JSON request and response is the norm. There are two ways to set the response format in Spray.

1) using respondWithMediaType

get {
  respondWithMediaType(`application/json`) {
    complete {
      //Some object response
    }
  }
}

In this method, each route/action would have to be explicitly set with media type of json. More info at https://github.com/spray/spray/wiki/Misc-Directives

2) Globally overriding the default format.

For all Json related operations, I am using Json4s as the json library. In the build.scala add the following json4s dependency. Note: you would need to reload the project in sbt and regenerate Eclipse. Eclipse does not refresh itself when new dependencies are added

In the CustomerServiceActor we will need to set the default Format to json4sFormats by adding the implicit formatter


    import spray.httpx.Json4sSupport
    import org.json4s.Formats
    import org.json4s.DefaultFormats
    import com.example.model.Customer

    class CustomerServiceActor extends Actor with CustomerService with AjaxService {
    implicit def json4sFormats: Formats = DefaultFormats
    . . . .

For example purpose, lets update the getCutomer action to return a mocked customer. The expected response should be a json formatted customer object.

path("getCustomer" / Segment) { customerId =>
  get {
    complete {
      val customer = Customer(
        id = Some(customerId),
        firstName = "Karthik",
        lastName = "Srinivasan"
      )
      customer //return customer obj
    }
  }
}

/*
[GET] http://localhost:8080/getCustomer/123
[Response] {"firstName":"Karthik","lastName":"S","id":"123", "city":"New York","country":"USA"}
*/

    //The customer case class is as follows:
    package com.example.model

case class Customer(
    firstName: String,
    lastName: String,
    id: Option[String] = None,
    phoneNumber: Option[String] = None,
    address: Option[String] = None,
    city: Option[String] = Some("New York"),
    country: Option[String] = Some("USA"),
    zipcode: Option[String] = None
) {}

To post a customer object and deserialize it to customer type, we can use spray entity [http://spray.io/documentation/1.1-M8/spray-httpx/unmarshalling/] and cast the post value to a JObject

import org.json4s.JsonAST.JObject

path("addCustomer") {
  post {
    entity(as[JObject]) { customerObj =>
      complete {
        val customer = customerObj.extract[Customer]
        //insert customer information into a DB and return back customer obj
        customer
      }
    }
  }
}

/*
[POST] http://localhost:8080/addCustomer { "firstName" : "karthik", "lastName" : "srinivasan", "zipcode" : "01010" }
[Should return] {"firstName":"karthik","lastName":"srinivasan","city":"New York","country":"USA","zipcode":"01010"}
*/

Further reading on json4s at https://github.com/json4s/json4s