Tomasz Nurkiewicz around Java and concurrency

In the first part we managed to connect to emojitracker.com and consume SSE stream that looks like this: data:{"1F60D":1} data:{"1F3A8":1,"1F48B":1,"1F499":1,"1F602":1,"2764":1} data:{"1F607":1,"2764":2} Each message represents the number of various emojis that appeared on Twitter since the previous message. After a few transformations, we got a stream of hexadecimal Unicode values for each emoji. E.g. for {"1F607":1,"2764":2} we produce three events: "1F607" , "2764" , "2764" . This is how we achieved it: import org.springframework.http.codec.ServerSentEvent; import org.springframework.web.reactive.function.client.WebClient; import reactor.core.publisher.Flux; import reactor.core.publisher.Mono; final Flux<String> stream = WebClient .create("http://emojitrack-gostreamer.herokuapp.com") .get().uri("/subscribe/e

In this article we will learn how to consume infinite SSE (server-sent events) stream with Spring's WebClient and Project Reactor . WebClient is a new HTTP client in Spring 5, entirely asynchronous and natively supporting Flux and Mono types. You can technically open thousands of concurrent HTTP connections with just a handful of threads. In standard RestTemplate one HTTP connection always needs at least one thread. As an example, let's connect to this cute little site called emojitracker.com . It shows emojis being used in real-time on Twitter. Looks quite cool! All credits go to Matthew Rothenberg , the creator of that site. It's very dynamic so there obviously has to be some push mechanism underneath. I wore my hacker glasses and after hours of penetration testing, I discovered the following URL in Chrome DevTools: http://emojitrack-gostreamer.herokuapp.com/subscribe/eps . If you connect to it, you'll get a fast stream of emoji counters: $ curl -v http://em