我们先定义一个打印报文的拦截器，继承Interceptor

public class LogInterceptor implements Interceptor {

    private static final String TAG = LogInterceptor.class.getSimpleName();

    @Override
    public Response intercept(Chain chain) throws IOException {
        Charset UTF8 = Charset.forName("UTF-8");

        // 打印请求报文
        Request request = chain.request();
        RequestBody requestBody = request.body();
        String reqBody = null;
        if(requestBody != null) {
            Buffer buffer = new Buffer();
            requestBody.writeTo(buffer);

            Charset charset = UTF8;
            MediaType contentType = requestBody.contentType();
            if (contentType != null) {
                charset = contentType.charset(UTF8);
            }
            reqBody = buffer.readString(charset);
        }
        Log.d(TAG, String.format("发送请求\nmethod：%s\nurl：%s\nheaders: %s\nbody：%s",
                request.method(), request.url(), request.headers(), reqBody));

        // 打印返回报文
        // 先执行请求，才能够获取报文
        Response response = chain.proceed(request);
        ResponseBody responseBody = response.body();
        String respBody = null;
        if(responseBody != null) {
            BufferedSource source = responseBody.source();
            source.request(Long.MAX_VALUE);
            Buffer buffer = source.buffer();

            Charset charset = UTF8;
            MediaType contentType = responseBody.contentType();
            if (contentType != null) {
                try {
                    charset = contentType.charset(UTF8);
                } catch (UnsupportedCharsetException e) {
                    e.printStackTrace();
                }
            }
            respBody = buffer.clone().readString(charset);
        }
        Log.d(TAG, String.format("收到响应\n%s %s\n请求url：%s\n请求body：%s\n响应body：%s",
                response.code(), response.message(), response.request().url(), reqBody, respBody));
        return response;
    }
}

然后通过OkHttp设置拦截器

private Retrofit getRetrofit() {
    OkHttpClient httpClient = new OkHttpClient.Builder()
            .addInterceptor(new LogInterceptor())
            .build();
    return new Retrofit.Builder()
            .client(httpClient)
            .addConverterFactory(GsonConverterFactory.create())
            .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
            .baseUrl(getBaseUrl())
            .build();
}

打印出来的报文如下所示

06-01 14:36:35.223 16547-16593/com.him.hisapp D/HttpServiceImpl: 发送请求
    method：POST
    url：http://www.yeyuanxinyi.com:6666/api/YeYuanXinYi
    headers: header1: headerValue1
    header2: headerValue2
    header3: headerValue3
    
    body：{"user_name":"yeyuanxinyi","age":"28","class":"3"}
06-01 14:36:39.003 16547-16593/com.him.hisapp D/HttpServiceImpl: 收到响应
    200 OK
    请求url：http://110.86.9.67:8401/api/VipSelfCashRegister/GetSysUser
    请求body：{"customerCode":"VIP","passWord":"666666","username":"00088"}
    响应body：{"success":true,"message":null,"code":null,"data":{"user_name":"yeyuanxinyi","age":"28","class":"3"}}