Java 21 Virtual Threads

Virtual threads v Java 21 umožňují miliony concurrent threads bez overhead platformních threadů.

Virtual threads¶

// Vytvoření virtual thread Thread.startVirtualThread(() -> { var result = fetchFromDB(); process(result); }); // ExecutorService s virtual threads try (var executor = Executors.newVirtualThreadPerTaskExecutor()) { List> futures = urls.stream() .map(url -> executor.submit(() -> fetch(url))) .toList(); for (var future : futures) { System.out.println(future.get()); } }

Spring Boot integrace¶

application.properties¶

spring.threads.virtual.enabled=true

Všechny request handlery běží na virtual threads!¶

Kdy použít¶

• I/O-bound operace (HTTP, DB, file)
• Vysoký počet concurrent requestů
• NE pro CPU-bound operace
• NE pro synchronized bloky (pinning)

Klíčový takeaway¶

Virtual threads = miliony concurrent threads. spring.threads.virtual.enabled=true a hotovo. Pozor na synchronized.