Concurrent HTTP with virtual threads

Code Comparison

ExecutorService pool =
    Executors.newFixedThreadPool(10);
List<Future<String>> futures =
    urls.stream()
    .map(u -> pool.submit(
        () -> fetchUrl(u)))
    .toList();
// manual shutdown, blocking get()

try (var exec = Executors
    .newVirtualThreadPerTaskExecutor()) {
    var results = urls.stream()
        .map(u -> exec.submit(
            () -> client.send(req(u),
                ofString()).body()))
        .toList().stream()
        .map(Future::join).toList();
}

Why the modern way wins

♾️

Thread per request

No pool sizing — one virtual thread per URL.

📖

Simple code

Write straightforward blocking code.

⚡

High throughput

Thousands of concurrent requests with minimal resources.

Old Approach

Thread Pool + URLConnection

Modern Approach

Virtual Threads + HttpClient

JDK Support

Concurrent HTTP with virtual threads

Available

Widely available since JDK 21 LTS (Sept 2023)

How it works

Virtual threads make it practical to create a thread per HTTP request. Combined with HttpClient, this replaces complex async callback patterns with simple blocking code that scales.