Android Retrofit2：在没有 GSON 或 JSONObject 的情况下序列化 null

Question

我的 Android 应用程序中 API 调用的结果可以是一个带有配置的 JSON，它映射到 SupportConfigurationJson 类，或者只是纯 null。当我得到一个 JSON 时，应用程序可以正常工作，但是当我得到 null 时，我得到了这个异常：

kotlinx.serialization.json.internal.JsonDecodingException: Expected start of the object '{', but had 'EOF' instead
    JSON input: null

我应该避免在这个项目中使用GSON。我还找到了一个解决方案，API 接口将返回Response<JSONObject>，之后我的存储库应检查此JSONObject 是否为空，如果不是，则将其映射到SupportConfigurationJson。但是在项目中，我们总是使用自定义类的响应，所以我想知道，有没有其他解决方案可以使用 null 或自定义数据类获得响应？

GettSupportConfiguration 用例类：

class GetSupportConfiguration @Inject constructor(
    private val supportConfigurationRepository: SupportConfigurationRepository
) {
    suspend operator fun invoke(): Result<SupportConfiguration?> {
        return try {
            success(supportConfigurationRepository.getSupportConfiguration())
        } catch (e: Exception) {
            /*
            THIS SOLUTION WORKED, BUT I DON'T THINK IT IS THE BEST WAY TO SOLVE THE PROBLEM
            if (e.message?.contains("JSON input: null") == true) {
                success(null)
            } else {
                failure(e)
            }
            */ 
                //I WAS USING THROW HERE TO SEE WHY THE APP ISN'T WORKING PROPERLY
            //throw(e)
            failure(e)
        }
    }
}

SupportConfigurationJson 类：

@Serializable
data class SupportConfigurationJson(
    @SerialName("image_url")
    val imageUrl: String,
    @SerialName("description")
    val description: String,
    @SerialName("phone_number")
    val phoneNumber: String?,
    @SerialName("email")
    val email: String?
)

SupportConfigurationRepository 类：

@Singleton
class SupportConfigurationRepository @Inject constructor(
    private val api: SupportConfigurationApi,
    private val jsonMapper: SupportConfigurationJsonMapper
) {

    suspend fun getSupportConfiguration(): SupportConfiguration? =
        mapJsonToSupportConfiguration(api.getSupportConfiguration().extractOrThrow())


    private suspend fun mapJsonToSupportConfiguration(
        supportConfiguration: SupportConfigurationJson?
    ) = withContext(Dispatchers.Default) {
        jsonMapper.mapToSupportSettings(supportConfiguration)
    }
}

fun <T> Response<T?>.extractOrThrow(): T? {
    val body = body()
    return if (isSuccessful) body else throw error()
}

fun <T> Response<T>.error(): Throwable {
    val statusCode = HttpStatusCode.from(code())
    val errorBody = errorBody()?.string()
    val cause = RuntimeException(errorBody ?: "Unknown error.")

    return when {
        statusCode.isClientError -> ClientError(statusCode, errorBody, cause)
        statusCode.isServerError -> ServerError(statusCode, errorBody, cause)
        else -> ResponseError(statusCode, errorBody, cause)
    }
}

SupportConfigurationApi 类：

interface SupportConfigurationApi {

    @GET("/mobile_api/v1/support/configuration")
    suspend fun getSupportConfiguration(): Response<SupportConfigurationJson?>
}

SupportConfigurationJsonMapper 类：

class SupportConfigurationJsonMapper @Inject constructor() {

    fun mapToSupportSettings(json: SupportConfigurationJson?): SupportConfiguration? {
        return if (json != null) {
            SupportConfiguration(
                email = json.email,
                phoneNumber = json.phoneNumber,
                description = json.description,
                imageUrl = Uri.parse(json.imageUrl)
            )
        } else null
    }
}

我这样创建改造：

@Provides
    @AuthorizedRetrofit
    fun provideAuthorizedRetrofit(
        @AuthorizedClient client: OkHttpClient,
        @BaseUrl baseUrl: String,
        converterFactory: Converter.Factory
    ): Retrofit {
        return Retrofit.Builder()
            .client(client)
            .baseUrl(baseUrl)
            .addConverterFactory(converterFactory)
            .build()
    }

@Provides
    @ExperimentalSerializationApi
    fun provideConverterFactory(json: Json): Converter.Factory {
        val mediaType = "application/json".toMediaType()
        return json.asConverterFactory(mediaType)
    }

Answer 1

一切都解释了here（1分钟阅读） Api 应该为 null 返回 "{}"，如果您无法更改 API，请将此转换器添加到 Retrofit

Answer 2

您正在与您的存储库直接交互，我建议使用

用例

与数据层交互。 因为您没有在此处捕获此异常，所以您的应用正在崩溃

suspend fun getSupportConfiguration(): SupportConfiguration? =
        mapJsonToSupportConfiguration(api.getSupportConfiguration().extractOrThrow())

Usecase 通常会捕获这些错误并在 ui 中显示有用的错误消息。