Java Magazine: Reactive Programming by Andrew Benstock

Author:Andrew Benstock [Benstock, Andrew]
Language: eng
Format: azw3
Publisher: UNKNOWN
Published: 2018-12-02T16:00:00+00:00

Reactive Spring

Proceeding from fundamentals, use the Spring Framework to quickly build a reactive application.

R

eactive programming is an approach to writing software that embraces asynchronous I/O. Asynchronous I/O is a small idea that portends big changes for software. The idea is simple: alleviate ineicient resource utilization by using resources that would otherwise sit idle as they waited for I/O activity. Asynchronous I/O inverts the normal design of I/O processing: clients are notiied of new data instead of asking for it. This approach frees the client to do other things while waiting for new notiications.

There is, of course, always the risk that too many notiications will overwhelm a client; so, a client must be able to push back, rejecting work it can’t handle. This is a fundamental aspect of low control in distributed systems. In reactive programming, the ability of the client to signal how much work it can manage is called back-pressure.

Many projects, such as Akka Streams, Vert.x, and RxJava, support reactive programming. [Vert.x and RxJava are examined in detail in the accompanying article, “Going Reactive with Eclipse Vert.x and RxJava,” on page 32. —Ed.] The Spring team has a project called Reactor, which provides reactive capabilities for the Spring Framework. There’s common ground across these diferent approaches, which has been summarized in the Reactive Streams initiative—an informal standard of sorts.

The Fundamental Data Types

The Reactive Streams initiative deines four data types.Publisher is a producer of values that might eventually arrive. A Publisher produces values of typeT, as shown in Listing 1.

Listing 1: The Reactive StreamsPublisher<T> package org.reactivestreams; public interface Publisher<T> {

void subscribe(Subscriber<? Super T> s);

}

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