使用场景：

甲方粑粑不积德，找外包公司给他们开发的时候，运气不好分配到实习生给你写SDK。然后可怕的就来了，这个SDK流落到你手上，让你来开发应用。
这就非常尴尬了。
该sdk让你这样用

BasicSdk sdk = new BasicSdk();
sdk.login(username,psw);
sdk.setOnlogin(new logincallback(){
    onLogin(LoginResult result){
    }
});

我当时就惊呆了，都0202年了，还有这种sdk吗。

但其实我们还是可以反抗一下的。用OkHttp的Interceptor。
比如说,参考他们sdk内部的实现，来实现我们的Interceptor逻辑
请求体的Interceptor

public class UserInterceptor implements Interceptor {
    @NonNull
    @Override
    public Response intercept(@NonNull Chain chain) throws IOException{
       Request request = chain.request();
        Request.Builder builder = request.newBuilder();
        //增加header，没问题
         builder.addHeader("requestId", requestId)
                    .addHeader("token",token);
 RequestBody body = request.body();
        if (body instanceof FormBody) {
            // 将参数组装成json格式
            FormBody formBody = (FormBody) body;
            JsonObject json = new JsonObject();
            int size = formBody.size();
            String name;
            String value;
            for (int i = 0; i < size; i++) {
                // 有些服务器不识别转码之后的字符串
                name = formBody.name(i);
                value = formBody.value(i);
                json.addProperty(name, value);
            }
            RequestBody newBody = RequestBody.create(JSON, json.toString());
            builder.method("POST", newBody);
        }
        //把请求体，重新构建成自己想要的样子，并返回
        return chain.proceed(builder.build());
  }
}

返回体的Interceptor

public class ResponseInterceptor implements Interceptor {
 @NonNull
    @Override
    public Response intercept(@NonNull Chain chain) throws IOException {
        Request request = chain.request();
        Response response = chain.proceed(request);
        ResponseBody responseBody = response.body();
        if (responseBody != null) {
            String responseString = responseBody.string();
            ...实现自己的解析
            ResponseBody newBody;

          //也可以throw一个Exception让后面的处理
          throw new CustomException()
          ....
          //把解析后重新拼接的内容放newBody然后返回
          return response.newBuilder()
                        .body(newBody)
                        .build();
        }

结合retrofit使用

public class UserService extends BaseHttpsService{
   // 保证只初始化一次，避免资源浪费
    private static volatile UserService userService;
    private UserApi api; //retrofit注解的接口

    public UserApi getApi() {
        return api;
    }

    private void initApi() {

        Gson gson = new GsonBuilder()
                .create();

        HttpLoggingInterceptor loggingInterceptor = new HttpLoggingInterceptor();
        loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
        //添加了请求体和返回体的拦截器
        OkHttpClient httpClient =builder
                .addInterceptor(AccountInterceptor.newInstance())
                .addInterceptor(ResponseInterceptor.newInstance())
                .addInterceptor(loggingInterceptor)
                .build();
        //构建retrofit对象
        Retrofit retrofit = new Retrofit.Builder()
                .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
                .addConverterFactory(GsonConverterFactory.create(gson))
                .baseUrl(ServerConfig.URL) //也可以这样指定baseUrl
                .client(httpClient)
                .build();
        api = retrofit.create(UserApi .class);
    }
}

配置https的基类BaseHttpsService

public class BaseHttpsService {
protected OkHttpClient.Builder builder;

    protected BaseHttpsService(){
        X509TrustManager xtm = new X509TrustManager() {
            @Override
            public void checkClientTrusted(X509Certificate[] chain, String authType) {
            }

            @Override
            public void checkServerTrusted(X509Certificate[] chain, String authType) {
            }

            @Override
            public X509Certificate[] getAcceptedIssuers() {
                return new X509Certificate[0];
            }
        };
 SSLContext sslContext;
        try {
            sslContext = SSLContext.getInstance("SSL");

            sslContext.init(null, new TrustManager[]{xtm}, new SecureRandom());

        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        } catch (KeyManagementException e) {
            e.printStackTrace();
        }
        SSLSocketFactory sslSocketFactory = new SSLSocketFactoryCompat(xtm);
        HostnameVerifier DO_NOT_VERIFY = (hostname, session) -> true;
        builder = new OkHttpClient.Builder()
                .writeTimeout(10, TimeUnit.SECONDS)
                .readTimeout(10, TimeUnit.SECONDS)
                .sslSocketFactory(sslSocketFactory, xtm)
                .hostnameVerifier(DO_NOT_VERIFY);
    }
}