HttpClient教程

1. HttpClient教程
   参考：https://www.yiibai.com/httpclient

2. 相关http库
   参考：https://www.cnblogs.com/liyuanhong/p/14353092.html

3. RestTemplate学习
   参考：https://zhuanlan.zhihu.com/p/78261630
   参考：https://blog.csdn.net/zzhongcy/article/details/104674808
   文档：https://docs.spring.io/spring-framework/docs/current/reference/html/integration.html#rest-resttemplate

4. WebClient学习
   参考:https://docs.spring.io/spring-framework/docs/current/reference/html/web-reactive.html#webflux-client
   参考：https://blog.csdn.net/zzhongcy/article/details/105412842