Circe Unmarshall HttpResponse

Question

I'm trying to ask consul for healthy services.The response is:

HttpResponse(200 OK,List(X-Consul-Index: 3471242, X-Consul-Knownleader: true, X-Consul-Lastcontact: 0, Date: Fri, 02 Mar 2018 16:06:08 GMT),HttpEntity.Strict(application/json,[{"Node":{"Node":"ci-content-1","Address":"10.45.200.14","TaggedAddresses":{"wan":"10.45.200.14"},"CreateIndex":2708577,"ModifyIndex":3470978},"Service":{"ID":"de62bdcb8e37:varnish_2:6085","Service":"shop-varnish-6085","Tags":null,"Address":"10.45.200.14","Port":33889,"EnableTagOverride":false,"CreateIndex":3313055,"ModifyIndex":3313055},"Checks":[{"Node":"ci-content-1","CheckID":"serfHealth","Name":"Serf Health Status","Status":"passing","Notes":"","Output":"Agent alive and reachable","ServiceID":"","ServiceName":"","CreateIndex":2708577,"ModifyIndex":3451134}]},{"Node":{"Node":"ci-content-2","Address":"10.45.200.18","TaggedAddresses":{"wan":"10.45.200.18"},"CreateIndex":2158463,"ModifyIndex":3471241},"Service":{"ID":"f89a94600d4c:varnish_1:6085","Service":"shop-varnish-6085","Tags":null,"Address":"10.45.200.18","Port":33622,"EnableTagOverride":false,"CreateIndex":3313064,"ModifyIndex":3313064},"Checks":[{"Node":"toom-ci-content-2","CheckID":"serfHealth","Name":"Serf Health Status","Status":"passing","Notes":"","Output":"Agent alive and reachable","ServiceID":"","ServiceName":"","CreateIndex":2158464,"ModifyIndex":3297480}]}]

The class definitions are:

final case class TaggedAddresses (
  wan: String)

final case class Node (
  node: String,
  address: String,
  taggedAddresses: TaggedAddresses,
  createIndex: Int,
  modifyIndex: Int
)

final case class Service (
  id: String,
  service: String,
  tags: String,
  addresses: String,
  port: Int,
  enableTagOverride: String,
  createIndex: Int,
  modifyIndex: Int
)

final case class Check (
  node: String,
  checkId:String,
  name: String,
  status: String,
  notes: String,
  output: String,
  serviceId: String,
  serviceName:String,
  createIndex: Int,
  modifyIndex: Int
)

final case class NodeInfo(
  node: Node,
  service: Service,
  checkList: List[Check]
)

package object VarnishInformation {}

Then I try to unmarshall:

val request = HttpRequest(method = HttpMethods.GET, uri = consulUrl)

val response = Await.result(Http().singleRequest(request), 10.seconds)

log.info("Entity: " + response.httpMessage)

val entries = Unmarshal(response).to[List[NodeInfo]]

and get the following error:

Error during processing of request: 'Attempt to decode value on failed cursor: DownField(node),DownArray'. Completing with 500 Internal Server Error response. To change default exception handling behavior, provide a custom ExceptionHandler.

Ican't see the failure, anybody else can do?

Answer 1

The short answer: Assuming you have all the required decoders and encoders in place, you should simply fix your case class as follows:

case class Node (
  Node: String,
  Address: String,
  TaggedAddresses: TaggedAddresses,
  CreateIndex: Int,
  ModifyIndex: Int
)

I.e., you have to use the tag names exactly as they appear in your JSON.

The long answer: if I'm taking out the relevant JSON from your object as follows:

val jsonString = 
"""
{
   "Node":{
     "Node":"ci-content-1",
     "Address":"10.45.200.14",
     "TaggedAddresses":{
       "wan":"10.45.200.14"
     },
   "CreateIndex":2708577,
   "ModifyIndex":3470978
 },
 ...
"""

Then the following code will yield Right(Node(ci-content-1,10.45.200.14,TaggedAddresses(10.45.200.14),2708577,3470978)), when the above, corrected version of the case class is used:

def myParse(jsonString: String) = {
  val res = parse(jsonString) match {
    case Right(json) => {
      val cursor = json.hcursor
      cursor.get[Node]("Node")
    }
    case _ => Left("Wrong JSON!") 
  }

  println(res)
}

Otherwise, I also get the same error you described.