Retrofit结合RxJava时Json序列化异常，RouteSchedule模型为空求助

Hey there! Let's work through this empty RouteSchedule model issue you're facing. The root problem here is almost certainly Gson not correctly locating the nested route-schedule array in your API response to map it to your model. Here are a few practical solutions to get your data loading properly:

1. Define an Outer Response Wrapper Class (Simplest Approach) #

First, let's assume your API returns a structure like this (common for nested data):

{
  "meta": { /* some metadata */ },
  "route-schedule": [
    { "stop-id": "123", "arrival-time": "08:00", ... }
  ]
}

Your current Retrofit interface is probably trying to return Single<RouteSchedule> directly, but Gson can't skip the outer wrapper to reach the array. Instead, create a dedicated class to represent the full API response:

public class RouteScheduleApiResponse {
    // Use @SerializedName to match the exact key from the API (including hyphens)
    @SerializedName("route-schedule")
    private List<RouteSchedule> routeScheduleList;

    // Getter for the schedule list
    public List<RouteSchedule> getRouteScheduleList() {
        return routeScheduleList;
    }
}

Then update your Retrofit interface to return this wrapper class:

public interface TransitApi {
    @GET("your-endpoint")
    Single<RouteScheduleApiResponse> getRouteSchedule();
}

When you subscribe, you can extract the array directly from the wrapper:

transitApi.getRouteSchedule()
    .subscribeOn(Schedulers.io())
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe(response -> {
        List<RouteSchedule> schedules = response.getRouteScheduleList();
        // Use your schedule data here
    }, error -> {
        // Handle error
    });

2. Use a Custom Gson Deserializer (No Wrapper Class Needed) #

If you don't want to add a wrapper class, you can create a custom deserializer to tell Gson exactly where to find the route-schedule array:

public class RouteScheduleDeserializer implements JsonDeserializer<List<RouteSchedule>> {
    @Override
    public List<RouteSchedule> deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) throws JsonParseException {
        // Navigate to the nested "route-schedule" array in the response
        JsonObject rootObject = json.getAsJsonObject();
        JsonArray scheduleArray = rootObject.getAsJsonArray("route-schedule");
        
        // Let Gson handle mapping the array items to RouteSchedule objects
        return context.deserialize(scheduleArray, new TypeToken<List<RouteSchedule>>(){}.getType());
    }
}

Next, register this deserializer when building your Retrofit instance:

// Build Gson with the custom deserializer
Gson customGson = new GsonBuilder()
    .registerTypeAdapter(
        new TypeToken<List<RouteSchedule>>(){}.getType(),
        new RouteScheduleDeserializer()
    )
    .create();

// Create Retrofit with the custom Gson converter
Retrofit retrofit = new Retrofit.Builder()
    .baseUrl(YOUR_BASE_URL)
    .addConverterFactory(GsonConverterFactory.create(customGson))
    .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
    .build();

Now your Retrofit interface can return Single<List<RouteSchedule>> directly, and Gson will automatically extract the nested array:

public interface TransitApi {
    @GET("your-endpoint")
    Single<List<RouteSchedule>> getRouteSchedule();
}

3. Double-Check Your RouteSchedule Model Annotations #

Don't overlook the basics! Make sure every field in your RouteSchedule class uses @SerializedName to match the exact key names from the API (especially those with hyphens, like stop-name or departure-time). Gson won't automatically map hyphenated keys to camelCase variable names unless you explicitly configure it:

public class RouteSchedule {
    @SerializedName("stop-id")
    private String stopId;
    
    @SerializedName("arrival-time")
    private String arrivalTime;
    
    // Add other fields with matching @SerializedName annotations
    // Getters and setters
}

If you have a lot of hyphenated keys, you can also configure Gson to handle this automatically:

Gson gson = new GsonBuilder()
    .setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_DASHES)
    .create();

But using @SerializedName is more explicit and less error-prone if your API has mixed naming conventions.

Quick Debugging Tip #

Add the HttpLoggingInterceptor to your Retrofit setup to print the raw API response. This will let you confirm that the route-schedule array actually exists in the response and matches the structure you're expecting:

HttpLoggingInterceptor logging = new HttpLoggingInterceptor();
logging.setLevel(HttpLoggingInterceptor.Level.BODY);

OkHttpClient client = new OkHttpClient.Builder()
    .addInterceptor(logging)
    .build();

// Add this client to your Retrofit builder
Retrofit retrofit = new Retrofit.Builder()
    .client(client)
    // ... other configs
    .build();

Any of these approaches should fix the empty model issue. Start with the wrapper class if you want a straightforward solution, or use the custom deserializer if you prefer to keep your interface clean.

内容的提问来源于stack exchange，提问作者Beraki