其实内部是封装了Okhttp和Gson解析

public class CourseFragmentAPI {
    public static void get(String userId, BaseCallBack<CourseFragmentResponseEntity> callBack){
        CourseFragmentService service = BaseRetrofit.getInstance().create(CourseFragmentService.class);
        Call<CourseFragmentResponseEntity> call = service.getData(userId);
        call.enqueue(callBack);
    }
}
public interface CourseFragmentService {
    @GET("courses/my_order_list")
    Call<CourseFragmentResponseEntity> getData(@Query("userId") String userId);

}
public class BaseRetrofit {
    private Retrofit retrofit;
    private static BaseRetrofit instance;

    private BaseRetrofit() {
        retrofit = new Retrofit.Builder().client(BaseOkHttpClient.getInstance()).baseUrl(Config.SERVER_URL).addConverterFactory(GsonConverterFactory.create()).build();
    }

    public static BaseRetrofit getInstance() {
        if (instance == null) {
            synchronized (BaseRetrofit.class) {
                if (instance == null) {
                    instance = new BaseRetrofit();
                }
            }
        }
        return instance;
    }

    public <T> T create(Class<T> service) {
        return retrofit.create(service);
    }
}
public class BaseOkHttpClient {
    public static OkHttpClient getInstance() {
        OkHttpClient.Builder httpClientBuilder = new OkHttpClient.Builder();
        httpClientBuilder.addInterceptor(new Interceptor() {
            @Override
            public Response intercept(Chain chain) throws IOException {
                Request originalRequest = chain.request();
                HttpUrl originalHttpUrl = originalRequest.url();
                HttpUrl.Builder builder = originalHttpUrl.newBuilder();

                EncodeParas(originalHttpUrl, builder);
                addCommonParas(builder);
                HttpUrl url = builder.build();
                Request.Builder requestBuilder = originalRequest.newBuilder()
                        .url(url)
                        .method(originalRequest.method(), originalRequest.body());

                Request request = requestBuilder.build();
                LogHelp.d("lyg", "request: " + request.method() + "  " + request.url());
                Response response = chain.proceed(request);

                MediaType contentType = null;
                String bodyString = null;
                if (response.body() != null) {
                    contentType = response.body().contentType();
                    bodyString = response.body().string();
                }
                LogHelp.d("lyg", "response: " + response.code() + "\n" + bodyString);
                if (response.body() != null) {// 深坑!打印body后原ResponseBody会被清空,需要重新设置body
                    ResponseBody body = ResponseBody.create(contentType, bodyString);
                    return response.newBuilder().body(body).build();
                } else {
                    return response;
                }
            }


        });
        return httpClientBuilder.build();
    }

    /**
     * 加密请求参数。debug模式不加密
     *
     * @param originalHttpUrl
     */
    private static void EncodeParas(HttpUrl originalHttpUrl, HttpUrl.Builder builder) {
        if (Config.isEncode) {
            String paras = generateXXTEAEncodedParas(getOriginURLEncodedParas(originalHttpUrl), generateUserSignature());
            String sign = generateAPPSignature(paras);
            clearAllParas(originalHttpUrl, builder);
            if (!TextUtils.isEmpty(paras)) {
                builder.addQueryParameter("paras", paras);
            }
            if (!TextUtils.isEmpty(sign)) {
                builder.addQueryParameter("sign", sign);
            }
        }
    }

    private static void addCommonParas(HttpUrl.Builder builder) {
        builder.addQueryParameter("appId", Constant.APPId)
                .addQueryParameter("ct", Constant.ClientType)
                .addQueryParameter("v", Constant.APIVersion)
                .addQueryParameter("ch", App.getAppChannel())
                .addQueryParameter("cv", App.getAppVsersion());
        LoginResponseEntity.Data data = UserData.getUser();
        if (!Config.isEncode && null != data && !TextUtils.isEmpty(data.getXuehuToken()) && data.getUserId() > 0) {
            builder.addQueryParameter("xuehuToken", data.getXuehuToken())
                    .addQueryParameter("userId", "" + data.getUserId());
        }
    }

    private static void clearAllParas(HttpUrl originalHttpUrl, HttpUrl.Builder builder) {
        Set<String> queryParameterNames = originalHttpUrl.queryParameterNames();
        for (String name : queryParameterNames) {
            builder.removeAllQueryParameters(name);
        }
    }

    private static String getOriginURLEncodedParas(HttpUrl originalHttpUrl) {
        StringBuilder builder = new StringBuilder();
        Set<String> queryParameterNames = originalHttpUrl.queryParameterNames();
        for (String name : queryParameterNames) {
            if (!TextUtils.isEmpty(builder.toString())) {
                builder.append("&");
            }
            builder.append(name + "=" + originalHttpUrl.queryParameter(name));
        }
        return builder.toString();

    }

    private static String generateUserSignature() {
        StringBuilder builder = new StringBuilder();
        String userSignLowerCase = ""; //Hmac签名
        String userSign = ""; //Hmac签名转大写,截取前32位
        String timeStamp = String.valueOf(System.currentTimeMillis());

        LoginResponseEntity.Data data = UserData.getUser();
        if (null != data && !TextUtils.isEmpty(data.getXuehuToken()) && data.getUserId() > 0 && !TextUtils.isEmpty(data.getUserKey())) {
            int stringAsciiSum = StringHelp.stringAsciiSum(data.getUserKey() + timeStamp);
            String content = data.getXuehuToken() + timeStamp + Constant.APIVersion;
            userSignLowerCase = Hmac.getSignature(content, data.getUserKey(), Constant.SignatureType[stringAsciiSum % 5]);
            LogHelp.d("lyg", "type: " + stringAsciiSum % 5);
        }
        if (!TextUtils.isEmpty(userSignLowerCase)) {
            if (userSignLowerCase.length() > 32) {
                userSign = userSignLowerCase.substring(0, 32).toUpperCase();
            } else {
                userSign = userSignLowerCase.toUpperCase();
            }
            builder.append("xuehuToken=" + data.getXuehuToken());
            builder.append("&userId=" + data.getUserId());
            builder.append("&timestamp=" + timeStamp);
            builder.append("&userSign=" + userSign);
        }
        return builder.toString();
    }

    private static String generateXXTEAEncodedParas(String urlEncodedOriginParas, String userSignature) {
        String content = "";
        if (!TextUtils.isEmpty(urlEncodedOriginParas)) {
            if (!TextUtils.isEmpty(userSignature)) {
                content = urlEncodedOriginParas + "&" + userSignature;
            } else {
                content = urlEncodedOriginParas;
            }
        } else if (!TextUtils.isEmpty(userSignature)) {
            content = userSignature;
        }
        if (!TextUtils.isEmpty(content)) {
            return XXTEA.encode(content, Constant.APPSecret).replace("\n", "");
        } else {
            return content;
        }
    }

    private static String generateAPPSignature(String xxteaEncodedOriginParas) {
        //appId+clientType+format+version+paras
        String signContent = Constant.APPId + Constant.ClientType + Constant.APIFormat + Constant.APIVersion + xxteaEncodedOriginParas;
        String sign = Hmac.getSignature(signContent, Constant.SignSecret, Constant.SignatureType[1]);
        if (!TextUtils.isEmpty(sign)) {
            return sign.toUpperCase();
        }

        return "";
    }
}