Deserialize nested object with GSON

Question

I'm trying to deserialize the following structure

{ meta: { keywords:  [a, b, c, d]}  ...  }

other valid structures are

{ meta: { keywords: "a,b,c,d"}  ... }

and

{ meta: {keywords: "a"}  ...}

I have this classes

public class Data {
   @PropertyName("meta")
   MetaData meta;
   ...
}


public class  MetaData {
    List<String> keywords;
    ...
}

and a custom deserializer

public static class CustomDeserilizer implements JsonDeserializer<MetaData>{
    @Override
    public MetaData deserialize(JsonElement json, Type typeOfT,  JsonDeserializationContext context) throws JsonParseException {
        List<String> keywords = null;
        Gson gson = new Gson();
        MetaData metaData = gson.fromJson(json, AppMetaData.class);
        JsonObject jsonObject = json.getAsJsonObject();

        if (jsonObject.has("keywords")) {
            JsonElement elem = jsonObject.get("keywords");
            if (elem != null && !elem.isJsonNull()) {

                if (jsonObject.get("keywords").isJsonArray()) {
                    keywords = gson.fromJson(jsonObject.get("keywords"),   new TypeToken<List<String>>() {
                    }.getType());
                } else {
                    String keywordString = gson.fromJson(jsonObject.get("keywords"), String.class);
                    keywords = new ArrayList<String>();
                    list.addAll(Arrays.asList(keywordString.split(",")));
                }
            }
        }
       metaData.setKeywords(keywords);
}

Then I try to apply the deserilizer:

Gson gson = new GsonBuilder()              
        .registerTypeAdapter(Data.class,new CustomDeserilizer())               
        .create();

But I get a parsing error , because is trying to deserialize Data instead of MetaData, how can I apply this deserializer to make it work right?

Answer 1

I solved it creating a deserializer for my class Data.

public static class DataDeserilizer implements JsonDeserializer {
    @Override
    public Data deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {

        Gson gson = new Gson();
        Data data = gson.fromJson(json, Data.class);
        JsonObject jsonObject = json.getAsJsonObject();
        if (jsonObject.has("meta")) {
            JsonElement elem = jsonObject.get("meta");
            if (elem != null && !elem.isJsonNull()) {

                Gson gsonDeserializer = new GsonBuilder()
                        .registerTypeAdapter(MetaData.class, new CustomDeserilizer())
                        .create();
                gsonDeserializer.fromJson(jsonObject.get("meta"), Data.class);
            }
        }

        return data;
    }



}

And

Gson gson = new GsonBuilder()              
    .registerTypeAdapter(Data.class,new DataDeserilizer())               
    .create();

Pretty obvious, but is there a more elegant solution?