Android Retrofit2.0 查看log和JSON字符串（HttpLoggingInterceptor）

Retrofit2.0 怎么打印请求到的json字符串和查看log呢？
关键类：HttpLoggingInterceptor
关键代码：

HttpLoggingInterceptor logging = new HttpLoggingInterceptor();
logging.setLevel(HttpLoggingInterceptor.Level.BODY);
httpClient = new OkHttpClient.Builder().addInterceptor(logging).build();

详细代码：

public static Retrofit initRetrofit(){
       OkHttpClient httpClient = new OkHttpClient();
       if (BuildConfig.DEBUG) {
            HttpLoggingInterceptor logging = new HttpLoggingInterceptor();
logging.setLevel(HttpLoggingInterceptor.Level.BODY);
httpClient = new OkHttpClient.Builder().addInterceptor(logging).build();
        }
        Gson gson = new GsonBuilder()
                .setDateFormat("yyyy-MM-dd'T'HH:mm:ssZ")
                .create();//使用 gson coverter，统一日期请求格式
        return new Retrofit.Builder()
                .baseUrl(BaseUtil.getGlivecApiUrl())
                .addConverterFactory(GsonConverterFactory.create(gson))
                .client(httpClient)
                .build();
     }

    /**
     * 创建 RetrofitManage 服务
     *
     * @return
    public static ApiService createApiService() {
        return

.client(httpClient)属性切莫忘记配置。

retrofit:2.0.0-beta4的依赖：

compile 'com.squareup.retrofit2:retrofit:2.0.0-beta4' // retrofit
compile 'com.google.code.gson:gson:2.5' // gson
compile 'com.squareup.retrofit2:converter-gson:2.0.0-beta4' 
compile 'com.squareup.retrofit2:adapter-rxjava:2.0.0-beta4' 
compile 'com.squareup.okhttp3:logging-interceptor:3.1.2'
compile 'com.squareup.okhttp3:okhttp:3.1.2'

也可以这么写：

public class RxService {
    private static final String BASETESTURL = "http://apis.baidu.com/showapi_open_bus/";
    private static OkHttpClient okHttpClient = new OkHttpClient.Builder().addInterceptor
            (new HttpLoggingInterceptor().setLevel(HttpLoggingInterceptor.Level.BODY)).build();
    private static Retrofit retrofit = new Retrofit.Builder()
            .baseUrl(BASETESTURL)
            .client(okHttpClient)
            .addCallAdapterFactory(RxJavaCallAdapterFactory.create())
            .addConverterFactory(GsonConverterFactory.create())
            .build();

    private RxService() {
        //construct

    }

    public static <T> T createApi(Class<T> clazz) {

        return