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/eps") …

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://emojitrack-gostr…