Android Dagger2 + OkHttp + Retrofit 依赖循环错误

Question

嘿，我正在使用 Dagger2、Retrofit 和 OkHttp，我面临着依赖循环问题。

当提供 OkHttp 时:

@Provides
@ApplicationScope
OkHttpClient provideOkHttpClient(TokenAuthenticator auth,Dispatcher dispatcher){
    return new OkHttpClient.Builder()
            .connectTimeout(Constants.CONNECT_TIMEOUT, TimeUnit.SECONDS)
            .readTimeout(Constants.READ_TIMEOUT,TimeUnit.SECONDS)
            .writeTimeout(Constants.WRITE_TIMEOUT,TimeUnit.SECONDS)
            .authenticator(auth)
            .dispatcher(dispatcher)
            .build();
}

当提供Retrofit时:

@Provides
@ApplicationScope
Retrofit provideRetrofit(Resources resources,Gson gson, OkHttpClient okHttpClient){
    return new Retrofit.Builder()
            .baseUrl(resources.getString(R.string.base_api_url))
            .addConverterFactory(GsonConverterFactory.create(gson))
            .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
            .client(okHttpClient)
            .build();
}

提供APIService时:

@Provides
@ApplicationScope
APIService provideAPI(Retrofit retrofit) {
    return retrofit.create(APIService.class);
}

我的 APIService 接口(interface):

public interface  APIService {
@FormUrlEncoded
@POST("token")
Observable<Response<UserTokenResponse>> refreshUserToken();

--- other methods like login, register ---

}

我的 TokenAuthenticator 类:

@Inject
public TokenAuthenticator(APIService mApi,@NonNull ImmediateSchedulerProvider mSchedulerProvider) {
    this.mApi= mApi;
    this.mSchedulerProvider=mSchedulerProvider;
    mDisposables=new CompositeDisposable();
}

@Override
public  Request authenticate(Route route, Response response) throws IOException {

    request = null;

    mApi.refreshUserToken(...)
            .subscribeOn(mSchedulerProvider.io())
            .observeOn(mSchedulerProvider.ui())
            .doOnSubscribe(d -> mDisposables.add(d))
            .subscribe(tokenResponse -> {
                if(tokenResponse.isSuccessful()) {
                    saveUserToken(tokenResponse.body());
                    request = response.request().newBuilder()
                            .header("Authorization", getUserAccessToken())
                            .build();
                } else {
                    logoutUser();
                }
            },error -> {

            },() -> {});

    mDisposables.clear();
    stop();
    return request;

}

我的日志:

Error:(55, 16) error: Found a dependency cycle:
com.yasinkacmaz.myapp.service.APIService is injected at com.yasinkacmaz.myapp.darkvane.modules.NetworkModule.provideTokenAuthenticator(…, mApi, …)
com.yasinkacmaz.myapp.service.token.TokenAuthenticator is injected at
com.yasinkacmaz.myapp.darkvane.modules.NetworkModule.provideOkHttpClient(…, tokenAuthenticator, …)
okhttp3.OkHttpClient is injected at
com.yasinkacmaz.myapp.darkvane.modules.NetworkModule.provideRetrofit(…, okHttpClient)
retrofit2.Retrofit is injected at
com.yasinkacmaz.myapp.darkvane.modules.NetworkModule.provideAPI(retrofit)
com.yasinkacmaz.myapp.service.APIService is provided at
com.yasinkacmaz.myapp.darkvane.components.ApplicationComponent.exposeAPI()

所以我的问题是:我的 TokenAuthenticator 类依赖于 APIService 但我需要在创建 APIService 时提供 TokenAuthenticator >。这会导致依赖循环错误。我该如何解决这个问题，有人面临这个问题吗？提前致谢。

Answer 1

你的问题是:

1. 您的 OKHttpClient 取决于您的 Authenticator
2. 您的身份验证器依赖于 Retrofit 服务
3. Retrofit 依赖于 OKHttpClient(如第 1 点)

因此循环依赖。

一个可能的解决方案是让您的 TokenAuthenticator 依赖于 APIServiceHolder 而不是 APIService。然后你的 TokenAuthenticator 可以在配置 OKHttpClient 时作为依赖项提供，而不管 APIService (在对象图的下方)是否已经被实例化.

一个非常简单的 APIServiceHolder:

public class APIServiceHolder {

    private APIService apiService;

    @Nullable
    APIService apiService() {
        return apiService;
    }

    void setAPIService(APIService apiService) {
        this.apiService = apiService;
    }
}

然后重构您的 TokenAuthenticator:

@Inject
public TokenAuthenticator(@NonNull APIServiceHolder apiServiceHolder, @NonNull ImmediateSchedulerProvider schedulerProvider) {
    this.apiServiceHolder = apiServiceHolder;
    this.schedulerProvider = schedulerProvider;
    this.disposables = new CompositeDisposable();
}

@Override
public  Request authenticate(Route route, Response response) throws IOException {

    if (apiServiceHolder.get() == null) {
         //we cannot answer the challenge as no token service is available

         return null //as per contract of Retrofit Authenticator interface for when unable to contest a challenge
    }    

    request = null;            

    TokenResponse tokenResponse = apiServiceHolder.get().blockingGet()

    if (tokenResponse.isSuccessful()) {
        saveUserToken(tokenResponse.body());
        request = response.request().newBuilder()
                     .header("Authorization", getUserAccessToken())
                     .build();
    } else {
       logoutUser();
    }

    return request;
}

请注意，检索 token 的代码应该是同步的。这是 Authenticator 契约的一部分。 Authenticator 中的代码将关闭 主线程。

当然，您需要为此编写@Provides 方法:

@Provides
@ApplicationScope
apiServiceHolder() {
    return new APIServiceHolder();
}

并重构提供者方法:

@Provides
@ApplicationScope
APIService provideAPI(Retrofit retrofit, APIServiceHolder apiServiceHolder) {
    APIService apiService = retrofit.create(APIService.class);
    apiServiceHolder.setAPIService(apiService);
    return apiService;
}

请注意，可变全局状态通常不是一个好主意。但是，如果您的包组织得很好，您可以适本地使用访问修饰符来避免持有者的意外使用。