在使用Retrofit時，有時候需要設定Set-Cookie等請求頭，如果每一個url都需要，那麼直接來個攔截器就好了。

官方說明：

• OkHttp3下OkHttpClient的 List< Interceptor> interceptors()方法，返回的是一個不可編輯的列表，如果對其進行編輯會報出UnSupportedOperationException
• Interceptor的典型使用場景，就是對request和response的Headers進行編輯

如下圖所示：

注意Header頭，不要照抄，要靈活運用。

讓所有網路請求都附上你的 token：

Interceptor mTokenInterceptor = new Interceptor() {
    @Override public Response intercept(Chain chain) throws IOException {
        Request originalRequest = chain.request();
        if (Your.sToken == null || alreadyHasAuthorizationHeader(originalRequest)) {
            return chain.proceed(originalRequest);
        }
        Request authorised = originalRequest.newBuilder()
            .header("Authorization"
 
, Your.sToken)
            .build();
        return chain.proceed(authorised);
    }
};

為OkHttpClient 新增兩個以上的攔截器，如下程式碼所示：

public class RestDataSource implements Repository {

    private final MarvelService mMarvelService;

    @Inject
    public RestDataSource() {
        // Log資訊
        HttpLoggingInterceptor loggingInterceptor = new
 
 HttpLoggingInterceptor();
        loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BASIC);

        // 公私密匙
        MarvelSigningInterceptor signingInterceptor = new MarvelSigningInterceptor(
                BuildConfig.MARVEL_PUBLIC_KEY, BuildConfig.MARVEL_PRIVATE_KEY);

        // OkHttp3.0的使用方式
        OkHttpClient client = new OkHttpClient.Builder()
                .addInterceptor(signingInterceptor)
                .addInterceptor(loggingInterceptor)
                .build();

        // 選擇人物資訊
        Gson customGsonInstance = new GsonBuilder()
                .registerTypeAdapter(new TypeToken<List<AvengersCharacter>>() {
                        }.getType(),
                        new MarvelResultsDeserializer<AvengersCharacter>())
                .create();

        // 介面卡
        Retrofit marvelApiAdapter = new Retrofit.Builder()
                .baseUrl(MarvelService.END_POINT)
                .addConverterFactory(GsonConverterFactory.create(customGsonInstance))
                .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
                .client(client)
                .build();

        // 服務
        mMarvelService = marvelApiAdapter.create(MarvelService.class);
    }

    // 返回人物資訊
    @Override
    public Observable<List<AvengersCharacter>> getCharacters(int currentOffset) {
        return mMarvelService.getCharacters(currentOffset);
    }
}

下面來個完整的配置：

import okhttp3.Interceptor;
import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
import retrofit2.Retrofit;

public class RetrofitAPIManager {

    public static final String SERVER_URL = "url";

    public static ClientAPI provideClientApi() {
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(SERVER_URL)
                .client(genericClient())
                .build();
        return retrofit.create(ClientAPI.class);
    }


    public static OkHttpClient genericClient() {
        OkHttpClient httpClient = new OkHttpClient.Builder()
                .addInterceptor(new Interceptor() {
                    @Override
                    public Response intercept(Chain chain) throws IOException {
                        Request request = chain.request()
                                .newBuilder()
                                .addHeader("Content-Type", "application/x-www-form-urlencoded; charset=UTF-8")
                                .addHeader("Accept-Encoding", "gzip, deflate")
                                .addHeader("Connection", "keep-alive")
                                .addHeader("Accept", "*/*")
                                .addHeader("Cookie", "add cookies here")
                                .build();
                        return chain.proceed(request);
                    }

                })
                .build();

        return httpClient;
    }
}