Mapping JSON with nested object to GSON

Question

I have a JSON schema class that is auto generate using AVRO. I would like to create a GSON object using this JSON. I try to do so using this code

    @Test
    public void parseJson() {

        JSONParser jsonParser = new JSONParser();
        try {
            JSONObject jsonObject = (JSONObject) jsonParser.parse(new FileReader("/pathto/test.json"));
            ThinEvent thinEvent = new Gson().fromJson(jsonObject.toString(), ThinEvent.class);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ParseException e) {
            e.printStackTrace();
        }
    }

but this results in the following error... It looks like GSON is looking for a string but the json actually contains a nested object? The ThinEvent object has refService declared as a list.

com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected a string but was BEGIN_OBJECT at line 1 column 74 path $.references[0].refService

private java.util.List<com.lm.gde.eventing.avro.Reference> references;

Here is my JSON, I have replaced some values with XXXX.

{
  "eventType": "policy.PolicyPremiumChangedEvent",
  "correlationId": "XXXX",
  "references": [
    {
      "ref": "XXX",
      "refType": "policy_id",
      "refService": {
        "com.lm.gde.eventing.avro.RefService": "policy_service"
      },
      "links": {
        "array": [
          {
            "refUri": ""
          }
        ]
      }
    },
    {
      "ref": "XXXXXX",
      "refType": "policy_number",
      "refService": {
        "com.lm.gde.eventing.avro.RefService": "policy_service"
      },
      "links": {
        "array": [
          {
            "refUri": "XXXXXX"
          }
        ]
      }
    },
    {
      "ref": "2019-09-28",
      "refType": "policy_tx_effective_date",
      "refService": {
        "com.lm.gde.eventing.avro.RefService": "policy_service"
      },
      "links": {
        "array": [
          {
            "refUri": "XXXXX"
          }
        ]
      }
    }
  ],
  "eventContext": null,
  "Timestamp": 1569574003295,
  "Version": "1"
}

Answer 1

GSON supports nested objects check this article . Just create model that matches the Json (but in Java/Kotlin) and toss it to GSON. Same with collections . You can even use List instead of arrays.

You could just get the json file as a complete string and deserialize that as well.