Mapping a trimmed response using ObjectMapper Or wrapping the response obtained

Question

Details ---

One of my POJO SomeResponseObject for an api response has attribute

@JsonProperty("s_summary")
private Map<String, SummaryObject> summary 

which further has few more attributes. These are summed in json as follows :

{  
 "s_summary": {
    "rewardSubscription": {
      "accountId": "XYZ",
      "startDate": "2015-12-29T19:00:00+05:30",
      "endDate": "2017-06-21T00:00:00+05:30",
      "isActive": true,
      "entityId": "ID123",
      "status": "ACTIVE"
    }
  }
}

This POJO(json) is further modified by our service to return a RESPONSE as :

{  
  "rewardSubscription": {
    "accountId": "XYZ",
    "startDate": "2015-12-29T19:00:00+05:30",
    "endDate": "2017-06-21T00:00:00+05:30",
    "isActive": true,
    "entityId": "ID123",
    "status": "ACTIVE"
  }
}

Narrowing Down ---

Now when we are writing tests against this API call. We end up being unable to map the response to any specific POJOs(java response class). Test code -

JSONObject responseObject = new JSONObject(responseFromService.getResponseBody())
      .getJSONObject("RESPONSE");
ObjectMapper objectMapper = new ObjectMapper();
SomeResponseObject summaryResponse = objectMapper.getObjectMapper()
      .readValue(responseObject.toString(), SomeResponseObject.class); // And this wouldn't work.

Question --

Is there any way we can cast the current API response or wrap it somehow to be mapped to the actual POJO(SomeResponseObject.class)?

Thanks in advance.

Answer 1

Problem

You receive an object with a rewardSubscription field, or, in your case, a map, with a rewardSubscription key. You can't convert a map to an object of SomeResponseObject type directly.

Solution

Option 1

Convert json to a map manually and set it to the SomeResponseObject instance:

JSONObject responseObject = new JSONObject(responseFromService.getResponseBody())
      .getJSONObject("RESPONSE");

ObjectMapper objectMapper = new ObjectMapper();
Map<String, SummaryObject> summaryMap = objectMapper.readValue(responseObject.toString(), new TypeReference<Map<String, SummaryObject>>() {});
SomeResponseObject response = new SomeResponseObject();
response.setSummaryMap(summaryMap);

Option 2

So as not to manually convert map each time, write a custom deserializer that will handle both cases. The deserialize method should be similar to this:

@Override
public SomeResponseObject deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException {
    ObjectMapper objectMapper = new ObjectMapper();
    JsonNode rootNode = jp.readValueAsTree();

    JsonNode sSummaryNode = rootNode.get("s_summary");
    if (sSummaryNode != null) {
        // Usual case.
        return objectMapper.treeToValue(sSummaryNode, SomeResponseObject.class);
    } else {
        // Special case - when received a map.
        Map<String, SummaryObject> summaryMap = objectMapper.readValue(rootNode.toString(), new TypeReference<Map<String, SummaryObject>>() {});
        SomeResponseObject response = new SomeResponseObject();
        response.setSummaryMap(summaryMap);
        return response;
    }
}

And then in the code you don't care:

ObjectMapper objectMapper = new ObjectMapper();
SomeResponseObject response = objectMapper.readValue(json, SomeResponseObject.class);