android - 如何使用 Retrofit 处理多个 API 端点？

Question

在我的 Android 项目中，我使用以下 Retrofit ApiModule 用于一个 API 端点。请注意，我使用 Dagger用于注入(inject)依赖项。

@Module(
        complete = false,
        library = true
)
public final class ApiModule {

    public static final String PRODUCTS_BASE_URL = "https://products.com";

    @Provides
    @Singleton
    Endpoint provideEndpoint() {
        return Endpoints.newFixedEndpoint(PRODUCTS_BASE_URL);
    }

    @Provides
    @Singleton
    ObjectMapper provideObjectMapper() {
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.setPropertyNamingStrategy(
            PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);
        return objectMapper;
    }

    @Provides
    @Singleton
    RestAdapter provideRestAdapter(
        Endpoint endpoint, ObjectMapper objectMapper) {
        return new RestAdapter.Builder()
                .setLogLevel(RestAdapter.LogLevel.NONE)
                .setEndpoint(endpoint)
                .setConverter(new JacksonConverter(objectMapper))
                .build();
    }

    @Provides
    @Singleton
    ProductsService provideProductsService(RestAdapter restAdapter) {
        return restAdapter.create(ProductsService.class);
    }

}

现在，我想与之通信的另一个 API(例如 "http://subsidiaries.com")。是否可以在重用 ObjectMapper 和 RestAdapter 的同时扩展给定的 ApiModule？还是我不应该延长它？我已经尝试复制模块。但这涉及到我必须复制 Endpoint、ObjectMapper 和...RestAdapter 有一个private 构造函数- 所以我不能。

Answer 1

我猜你可以使用 Named 注释:

@Module(
        complete = false,
        library = true
)
public final class ApiModule {

    public static final String PRODUCTS_BASE_URL = "https://products.com";
    public static final String SUBSIDIARIES_BASE_URL = "https://subsidiaries.com";

    public static final String PRODUCTS = "products";
    public static final String SUBSIDIARIES = "subsidiaries";

    @Provides
    @Singleton
    @Named(PRODUCTS)
    Endpoint provideProductsEndpoint() {
        return Endpoints.newFixedEndpoint(PRODUCTS_BASE_URL);
    }

    @Provides
    @Singleton
    @Named(SUBSIDIARIES)
    Endpoint provideSubsidiariesEndpoint() {
        return Endpoints.newFixedEndpoint(SUBSIDIARIES_BASE_URL);
    }

    @Provides
    @Singleton
    ObjectMapper provideObjectMapper() {
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.setPropertyNamingStrategy(
            PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);
        return objectMapper;
    }

    @Provides
    @Singleton
    @Named(PRODUCTS)
    RestAdapter provideProductsRestAdapter(@Named(PRODUCTS) Endpoint endpoint, ObjectMapper objectMapper) {
        return newRestAdapterBuilder(objectMapper)
                .setEndpoint(endpoint)
                .build();
    }

    @Provides
    @Singleton
    @Named(SUBSIDIARIES)
    RestAdapter provideSubsidiariesRestAdapter(@Named(SUBSIDIARIES) Endpoint endpoint, ObjectMapper objectMapper) {
        return newRestAdapterBuilder(objectMapper)
                .setEndpoint(endpoint)
                .build();
    }

    @Provides
    @Singleton
    @Named(PRODUCTS)
    ProductsService provideProductsService(@Named(PRODUCTS) RestAdapter restAdapter) {
        return restAdapter.create(ProductsService.class);
    }

    @Provides
    @Singleton
    @Named(SUBSIDIARIES)
    ProductsService provideSubsidiariesService(@Named(SUBSIDIARIES) RestAdapter restAdapter) {
        return restAdapter.create(ProductsService.class);
    }

    private RestAdapter.Builder newRestAdapterBuilder(ObjectMapper objectMapper) {
        return new RestAdapter.Builder()
                       .setLogLevel(RestAdapter.LogLevel.NONE)
                       .setConverter(new JacksonConverter(objectMapper));
    }
}

现在，在注入(inject) ProductsService 的任何地方，您都需要使用 @Named(PRODUCTS) 或 @Named(SUBSIDIARIES) 注释依赖关系，取决于您需要哪种变体。当然，除了 @Named 注释之外，您还可以创建自己的自定义注释并使用它们。参见 here在“限定符”下。

要稍微扁平化您的模块，您可以将 RestAdapter 的创建移动到 provide*Service() 方法中，并摆脱 provide*RestAdapter() 方法.当然，除非您需要 RestAdapters 作为模块外部的依赖项。