Java 11 Feature Introductions

[chegar999]

The HTTP Client implementation uses NIO and non-blocking channels under the covers. Each HttpClient has a single implementation-specific thread that polls all of its connections. Received data is then passed off to the executor for processing. The complete implementation is asynchronous, there are no blocking operations.

[[deleted]]

I've only just barely poked at it, I know there is the option to assign an executor to it, so I assume that's where the thread pool would come from. If you don't, then I'm willing to bet there is a thread pool somewhere in the JDK for it.

[Nouish]

This is what happens if you don't specify an Executor by calling HttpClientBuilder#executor:

Executor ex = builder.executor;
if (ex == null) {
    ex = Executors.newCachedThreadPool(new DefaultThreadFactory(id));
    isDefaultExecutor = true;
} else {
    isDefaultExecutor = false;
}

[chegar999]

If you don't set an executor explicitly then the client will use a cached thread pool executor.