How to I deserialize different json response for the same request to different bean object

for example, for the same request, the server may return:

{
  "code":200,
  "data":{
    "xxx":"xxx"
  }
}

or:

{
  "code":666,
  "error":"error detail"
}

And I’m using Android and Retrofit, so how should I handle this desrialization task?

the above question could be summarized as: how could hanndle deserialization on different condition(the json struction of response may differ)?

Or maybe should I adjust the response structure? But many 3rdparty api return stuff just like above so It’s impossible to adjust the response structure.

[Marcono1234]

You can solve this by implementing a custom JsonDeserializer or TypeAdapterFactory. JsonDeserializer parses the JSON data into an in-memory representation of JsonElement (and subtypes). TypeAdapterFactory creates TypeAdapter instances which read the JSON data from the stream and are therefore more efficient. However, TypeAdapterFactory can only be used if code is always the first member in the JSON data because its value is needed to determine how to parse the JSON data.

The following uses JsonDeserializer:

public class GsonTypeSelectingTest {
    static class DataBody {
        public String xxx;
        
        @Override
        public String toString() {
            return "{xxx=" + xxx + "}";
        }
    }
    
    static abstract class Response {
        // Use a constant to make sure field name here and in JsonDeserializer match
        public static final String CODE_NAME = "code";
        
        @SerializedName(CODE_NAME)
        public int code;
    }
    
    static class SuccessResponse extends Response {
        public DataBody data;
        
        @Override
        public String toString() {
            return "success{code=" + code + ",data=" + data + "}";
        }
    }
    
    static class ErrorResponse extends Response {
        public String error;
        
        @Override
        public String toString() {
            return "error{code=" + code + ",error=" + error + "}";
        }
    }
    
    static class ResponseDeserializer implements JsonDeserializer<Response> {
        public static final ResponseDeserializer INSTANCE = new ResponseDeserializer();
        
        private ResponseDeserializer() {
        }
        
        @Override
        public Response deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
            // Get `code` and depending on its value choose correct subclass
            int code = json.getAsJsonObject().get(Response.CODE_NAME).getAsInt();
            if (code == 200) {
                return context.deserialize(json, SuccessResponse.class);
            } else {
                return context.deserialize(json, ErrorResponse.class);
            }
        }
    }
    
    public static void main(String[] args) {
        // Should use `static final` field to reuse Gson
        Gson gson = new GsonBuilder()
            .registerTypeAdapter(Response.class, ResponseDeserializer.INSTANCE)
            .create();
        
        System.out.println(gson.fromJson("{\"code\":200,\"data\":{\"xxx\":\"test\"}}", Response.class));
        System.out.println(gson.fromJson("{\"code\":666,\"error\":\"error-detail\"}", Response.class));
    }
}

[Marcono1234]

I am closing this because I think this has been answered. Please let us know if you still have questions regarding this.