https://www.youtube.com/watch?v=M3jNn3HMeWg
也就是说原来的请求基于Servlet,每个线程要单独请求 而WebFlux基于NIO和事件循环,使用request event response event 来做了封装
Mono 0-1个, Flux 多个 需要配合Reactive DB
when get data ,subscribe the publisher and push data to client
