如何使用带有Gson的retrofit2将空字符串视为null

import com.google.gson.*;

import java.lang.reflect.Type;

public class EmptyStringToNullDeserializer implements JsonDeserializer<String> {
    @Override
    public String deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
        String value = json.getAsString();
        if (value.isEmpty()) {
            return null;
        }
        return value;
    }
}

import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class RetrofitClient {
    private static Retrofit retrofit;

    public static Retrofit getClient(String baseUrl) {
        if (retrofit == null) {
            Gson gson = new GsonBuilder()
                    .registerTypeAdapter(String.class, new EmptyStringToNullDeserializer())
                    .create();

            retrofit = new Retrofit.Builder()
                    .baseUrl(baseUrl)
                    .addConverterFactory(GsonConverterFactory.create(gson))
                    .build();
        }
        return retrofit;
    }
}

import retrofit2.Call;
import retrofit2.http.GET;

public interface ApiService {
    @GET("example")
    Call<ApiResponse> getExample();
}

public class ApiResponse {
    private String data;

    public String getData() {
        return data;
    }
}

import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;

public class ExampleActivity {
    private ApiService apiService;

    public void fetchData() {
        Call<ApiResponse> call = apiService.getExample();
        call.enqueue(new Callback<ApiResponse>() {
            @Override
            public void onResponse(Call<ApiResponse> call, Response<ApiResponse> response) {
                if (response.isSuccessful()) {
                    ApiResponse apiResponse = response.body();
                    String data = apiResponse.getData();
                    // 处理数据
                }
            }

            @Override
            public void onFailure(Call<ApiResponse> call, Throwable t) {
                // 处理错误
            }
        });
    }
}