Hands-On Reactive Programming in Spring 5

Asynchronous HTTP with Spring Web MVC

The introduced in Servlet 3.0 asynchronous support expands the ability to process an HTTP request in non-container threads. Such a feature is pretty useful for long-running tasks. With those changes, in Spring Web MVC we can return not only a value of type T in @Controller but also a Callable<T> or a DeferredResult<T>. The Callable<T> may be run inside a non-container thread, but still, it would be a blocking call. In contrast, DeferredResult<T> allows an asynchronous response generation on a non-container thread by calling the setResult(T result) method so it could be used within the event-loop.

Starting from version 4.2, Spring Web MVC makes it possible to return ResponseBodyEmitter, which behaves similarly ...