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

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

I know I am late, but I just want to share my thought. I was working on a project where I am writing a method. The method uses retrofit to get data from server. Since other developers in my company will use this method, I could not use a POJO class (in your example, the TrackerRefResponse class). So I used JsonObject / Object like this:

interface APIService.java

public class APIService{
    @FormUrlEncoded
    @POST
    Call<JsonObject> myPostMethod(@Url String url, @Field("input") String input);
}

Then in my method, I wrote this:

Call<JsonObject> call = RetrofitClient.getAPIService().establishUserSession(post_request_url, someParameter);

call.enqueue(new Callback<JsonObject>() {
            @Override
            public void onResponse(Call<JsonObject> call, Response<JsonObject> response) {
                JsonObject jsonObject = response.body();
                String jsonString = response.body().toString();
                // then do your stuff. maybe cast to object using a factory pattern  
    }
// rest of the code
}

You can also use Object instead of 'JsonObject`. Later, when you will know which kind of response it is, maybe you can cast this into desired object.

Answer 3

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.

Answer 4

Any of your possible solutions will work. What you can also do is send the Retrofit api interface return type to response. With that response you get a body Inputstream which you can convert to a JSON Object and read as you see fit.

Look at: http://square.github.io/retrofit/#api-declaration - under RESPONSE OBJECT TYPE

Updated

Retrofit 2 is out now and with it some changes to the documentation and library.

Look at http://square.github.io/retrofit/#restadapter-configuration there are request and response body object that can be used.