android - Retrofit 2.0 处理 json 响应中的错误

Question

我正在研究 Retrofit 2.0(非常棒)来处理 API 响应。当 API 成功响应时一切正常，我从 json 响应返回转换后的对象

请求示例:

ServiceAPI.getUser(new Callback<User>() {
    @Override
    public void onResponse(Call<User> call, Response<User> response) {
       User user = response.body(); // user is my POJO
    }

    @Override
    public void onFailure(Call<User> call, final Throwable t) {
        Log.e(TAG, "Error: " + t.getMessage())
    }
});

响应完成后，我返回 POJO(这是我的主要目的)，而不是要解析的 json，以避免样板。

所以这里是我的代码来处理这个:

// the interface to handle calls
protected interface ServiceAPI {
    @GET("/user/{userId}")
    Call<User> getUser(@Path("userId") String userId);
}

// the GSON part for converting data
Gson gson = new GsonBuilder()
    .registerTypeAdapterFactory(new ItemTypeAdapterFactory())
    .setDateFormat("yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'SSS'Z'")
    .create();

// an interceptor to log requests responses
OkHttpClient okClient = new OkHttpClient.Builder()
    .addInterceptor(new LogJsonInterceptor())
    .build();

// the retrofit builder
retrofit = new Retrofit.Builder()
    .baseUrl(mBaseUrl)
    .client(okClient)
    .addConverterFactory(GsonConverterFactory.create(gson))
    .build();

// the interceptor to log requests
public static class LogJsonInterceptor implements Interceptor {
    @Override
    public okhttp3.Response intercept(Interceptor.Chain chain) throws IOException {
        Request request = chain.request();
        okhttp3.Response response = chain.proceed(request);
        String rawJson = response.body().string();
        Log.d(TAG, rawJson);
        // Re-create the response before returning it because body can be read only once
        return response.newBuilder().body(ResponseBody.create(response.body().contentType(), rawJson)).build();
    }
}

// here the magic to handle json response and get data from "data" json key
public static class ItemTypeAdapterFactory implements TypeAdapterFactory {

    public <T> TypeAdapter<T> create(Gson gson, final TypeToken<T> type) {

        final TypeAdapter<T> delegate = gson.getDelegateAdapter(this, type);
        final TypeAdapter<JsonElement> elementAdapter = gson.getAdapter(JsonElement.class);

        return new TypeAdapter<T>() {

            public void write(JsonWriter out, T value) throws IOException {
                delegate.write(out, value);
            }

            private RestError error;

            public T read(JsonReader in) throws IOException {

                JsonElement jsonElement = elementAdapter.read(in);
                if (jsonElement.isJsonObject()) {
                    JsonObject jsonObject = jsonElement.getAsJsonObject();
                    if (jsonObject.has("data")) {
                        jsonElement = jsonObject.get("data");
                    }
                }

                return delegate.fromJsonTree(jsonElement);
            }
        }.nullSafe();
    }
}

// here the method to call from an activity for example to get an User
public static void getUser(final String userId, final Callback<User> callback) {
    serviceAPI.getUser(userId).enqueue(new Callback<User>() {
        @Override
        public void onResponse(Call<User> call, Response<User> response) {
            callback.onResponse(call, response);
        }

        @Override
        public void onFailure(Call<User> call, Throwable t) {
            callback.onFailure(call, t);
        }
    });
}

// here the call from the Activity
ServiceAPI.getUser(new Callback<User>() {
    @Override
    public void onResponse(Call<User> call, Response<User> response) {
       User user = response.body();
    }

    @Override
    public void onFailure(Call<User> call, final Throwable t) {
        Log.e(TAG, "Error: " + t.getMessage())
    }
});

// when API answers with success (code 200 from headers)
{
"data":
    {
        "id":1,
        "name":"myname",
        "email":"myemail"
    }
}

所以这里一切正常，因为我从“数据”获得响应并将响应转换为我的 POJO

问题:但是当 API 回答错误时(还有来自 header 的代码 200)，我得到这个:

{
"error":
    {
        "code":200
        "type":"OAuth_exception",
        "message":"You need an access token to get an user",
    }
}

问题是 retrofit “响应”仍然成功并且 errorBody 为空

所以在这里，我会把它转换成一个 RestError POJO(下面)并在调用 getUser 方法时将它发送到调用中

public class RestError {
    private int code;
    private String message;
    private String type;

    public RestError(int code, String message, String type) {
        this.code = code;
        this.message = message;
        this.type = type;
    }
}

有解决办法吗？

更新:

我在 ItemTypeAdatperFactory 中添加了这个

public T read(JsonReader in) throws IOException {

                    JsonElement jsonElement = elementAdapter.read(in);
                    if (jsonElement.isJsonObject()) {
                        JsonObject jsonObject = jsonElement.getAsJsonObject();
                        if (jsonObject.has("data")) {
                            jsonElement = jsonObject.get("data");
                        } else if (jsonObject.has("error")) {
                            jsonElement = jsonObject.get("error");

                            TypeAdapter<RestError> restErrorTypeAdapter = gson.getAdapter(RestError.class);
                            RestError error = restErrorTypeAdapter.fromJsonTree(jsonElement);
                            return (T) error;
                        }
                    }

                    return delegate.fromJsonTree(jsonElement);
                }

然后我像这样创建了一个自定义回调:

public abstract static class CustomCallback<T> implements Callback<T> {

    public abstract void onError(RestError error);
    public abstract void onSuccess(T body);

    @Override
    public void onResponse(Call<T> call, Response<T> response) {
        if(response.body() instanceof RestError) {
            onError((RestError) response.body());
        } else {
            onSuccess(response.body());
        }
    }

    @Override
    public void onFailure(Call<T> call, Throwable t) {
        Log.e(TAG, t.toString());
    }
}

那么现在调用是怎样的:

ServiceAPI.getUser(new ServiceAPI.CustomCallback<User>() {
        @Override
        public void onError(RestError error) {
            Log.e(TAG, error.toString());
        }

        @Override
        public void onSuccess(User body) {
            Log.d(TAG, body.toString());  
            User user = body;  
        }

        @Override
        public void onFailure(Call<User> call, Throwable t) {
            Log.e(TAG, t.toString());
        }
    });

所以现在当发生错误时，我从 onError() 获取它，否则从 onSuccess() 获取它并且似乎完成了工作

你在想什么？

Answer 1

您可以从某个 Response 类扩展所有 POJO，该类将包含字段 RestError error。然后你可以制作一些 isSuccessful 方法，它会检查 error 字段是否为 null 并正确处理它。