How to handle Dynamic JSON in Retrofit?

Question

I am using the retrofit efficient networking library, but I am unable to handle Dynamic JSON which contains single prefix responseMessage which changes to object randomly, the same prefix ( responseMessage) changes to String in some cases (dynamically).

Json format Object of responseMessage:

{    "applicationType":"1",    "responseMessage":{       "surname":"Jhon",       "forename":" taylor",       "dob":"17081990",       "refNo":"3394909238490F",       "result":"Received"    }  } 

responseMessage Json format dynamically changes to type string:

 {        "applicationType":"4",        "responseMessage":"Success"            } 

My problem is since retrofit has built-in JSON parsing, I have to assign single POJO per request! but the REST-API unfortunately, is built on dynamic JSON responses. The prefix will change from string to object randomly in both success(...) and failure(...) methods!

void doTrackRef(Map<String, String> paramsref2) {     RestAdapter restAdapter = new RestAdapter.Builder().setEndpoint("http://192.168.100.44/RestDemo").build();        TrackerRefRequest userref = restAdapter.create(TrackerRefRequest.class);     userref.login(paramsref2,             new Callback<TrackerRefResponse>() {                 @Override                 public void success(                         TrackerRefResponse trackdetailresponse,                         Response response) {                      Toast.makeText(TrackerActivity.this, "Success",                     Toast.LENGTH_SHORT).show();                  }                  @Override                 public void failure(RetrofitError retrofitError) {                       Toast.makeText(TrackerActivity.this, "No internet",                         Toast.LENGTH_SHORT).show();                 }               }); } 

Pojo:

public class TrackerRefResponse {   private String applicationType;      private String responseMessage;          //String type  //private ResponseMessage responseMessage;  //Object of type ResponseMessage  //Setters and Getters   } 

In above code POJO TrackerRefResponse.java prefix responseMessage is set to string or object of type responseMessage , so we can create the POJO with ref variable with same name (java basics :) ) so I'm looking for same solution for dynamic JSON in Retrofit. I know this is very easy job in normal http clients with async task, but it's not the best practice in the REST-Api JSON parsing! looking at the performance Benchmarks always Volley or Retrofit is the best choice, but I'm failed handle dynamic JSON!

Possible solution I Know

1. Use old asyc task with http client parsing. :(

2. Try to convince the RESTapi backend developer.

3. Create custom Retrofit client :)

Answer 1

Late to the party, but you can use a converter.

RestAdapter restAdapter = new RestAdapter.Builder()     .setEndpoint("https://graph.facebook.com")     .setConverter(new DynamicJsonConverter()) // set your static class as converter here     .build();  api = restAdapter.create(FacebookApi.class); 

Then you use a static class which implements retrofit's Converter:

static class DynamicJsonConverter implements Converter {      @Override public Object fromBody(TypedInput typedInput, Type type) throws ConversionException {         try {             InputStream in = typedInput.in(); // convert the typedInput to String             String string = fromStream(in);             in.close(); // we are responsible to close the InputStream after use              if (String.class.equals(type)) {                 return string;             } else {                 return new Gson().fromJson(string, type); // convert to the supplied type, typically Object, JsonObject or Map<String, Object>             }         } catch (Exception e) { // a lot may happen here, whatever happens             throw new ConversionException(e); // wrap it into ConversionException so retrofit can process it         }     }      @Override public TypedOutput toBody(Object object) { // not required         return null;     }      private static String fromStream(InputStream in) throws IOException {         BufferedReader reader = new BufferedReader(new InputStreamReader(in));         StringBuilder out = new StringBuilder();         String line;         while ((line = reader.readLine()) != null) {             out.append(line);             out.append("\r\n");         }         return out.toString();     } } 

I have written this sample converter so it returns the Json response either as String, Object, JsonObject or Map< String, Object >. Obviously not all return types will work for every Json, and there is sure room for improvement. But it demonstrates how to use a Converter to convert almost any response to dynamic Json.

Answer 2

RestClient.java

import retrofit.client.Response; public interface RestClient {   @GET("/api/foo") Response getYourJson(); } 

YourClass.java

RestClient restClient;  // create your restClient  Response response = restClient.getYourJson();  Gson gson = new Gson(); String json = response.getBody().toString(); if (checkResponseMessage(json)) {   Pojo1 pojo1 = gson.fromJson(json, Pojo1.class); } else {   Pojo2 pojo2 = gson.fromJson(json, Pojo2.class); } 

You must implement "checkResponseMessage" method.