Http client调研以及封装

[Draymonders]

• http 规范 https://developer.mozilla.org/zh-CN/docs/Web/HTTP/Basics_of_HTTP/Identifying_resources_on_the_Web

[Draymonders]

• restTemplate
• okhttp
• apache httpClient

[Draymonders]

最终选用okhttp, 因为支持https和http2，方便后续更深入的学习