Spring Webflux Interview Questions


What Is Reactive Programming?

Reactive programming is about non-blocking, event-driven applications that scale with a small number of threads, with backpressure being a key ingredient that aims to ascertain engenderers don't inundate consumers.
The primary benefits of reactive programming are:
  • Incremented utilization of computing resources on multicore and multi-CPU hardware
  • Incremented performance by truncating serialization


What is Spring Web flux?

Spring WebFlux is Spring's reactive-stack web framework, and it's an alternative to Spring MVC. Spring WebFlux is a web framework that’s built on top of Project Reactor, to give you asynchronous I/O, and sanction our application to perform better.
Reactive web programming is great for applications that have streaming data and clients that consume it and stream it to their users. It ain’t great for developing CRUD apps.

What are the advantages of Spring Webflux?

A non-blocking approach that makes it possible to handle concurrency with a small number of threads and to scale effectively,
Functional programming, which avails inscribe more declarative code with the utilization of fluent APIs.

What is the Publisher?

The publisher is the source that will send the data to one or more subscribers.
A Publisher (for example Publisher<Object>) can return zero or multiple, possibly infinite, results. To make it more clear how many results we can expect, Project Reactor  introduced two implementations of Publisher:
  • A Mono<T>, which can either return zero or one result afore consummating,
  • And a Flux<T>, which can return zero to many, possibly infinite, results afore consummating.


What is the Mono?

The first type of publisher is a Mono. The Mono API sanctions us to emit only a single value, after which it will immediately consummate. This denotes that the Mono is the reactive obverse of returning a simple object or an Optional.

What is the Flux?

Flux is used to handle zero to many results, possibly even infinite results.

What is the Subscriber?

A subscriber will subscribe itself to a publisher, will designate how much data the publisher may send, and will process the data.

What is the Subscription?

Defines a one-to-one relationship between a Publisher and a Subscriber. It can only be used once by a single Subscriber. It is utilized to both signal desire for data and sanctions resource cleanup.

What is the Processor?

Represents a processing stage consisting of both a Subscriber and a Publisher and obeys the contracts of both.

What Is the Use of WebClient and WebTestClient?

WebClient is a component that can act as a reactive client for performing non-blocking HTTP requests. Being a reactive client, it can handle reactive streams with backpressure, and it can thoroughly capitalize on Java lambdas. It can withal handle both sync and async scenarios.
WebTestClient class is used for testing. It can connect to any server over an HTTP connection. It can additionally bind directly to WebFlux applications utilizing mock request and replication objects, without the desideratum for an HTTP server.

What is the difference between Spring MVC Async and Spring Webflux?

  • Spring Async I/O model during its communication with the client is blocking. It may cause a performance quandary with slow clients. On the other hand, Spring WebFlux provides a non-blocking I/O model.
  • Reading the request body or request components is blocking in Spring Async, whiles it is non-blocking in Spring WebFlux.
  • In Spring Async, Filters and Servlets are working synchronously, but Spring WebFlux fortifies full asynchronous communication.
  • Spring WebFlux is compatible with wider ranges of Web/Application servers than Spring Async, like Netty, and Undertow.

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