Spring WebFlux is a part of the Spring Framework that provides reactive programming support for web applications. It introduces reactive types like Mono and Flux publishers which are fundamental to its programming model. Mono and Flux play crucial roles in reactive programming. The reactive programming introduces a lot of operators to handle the business logic like flatmap, onErrorResume, map, zip, just, and other reactor operators. In this article, we explain what flatmap and switchIfEmpty.

Prerequisites:

To understand this content, you should know the topics below are easy to understand.

• Spring Framework
• Spring Reactor Programming
• Publisher and Consumer Concepts
• Event flow in Reactive Streams
• Operators in Spring Reactor
• Concept of Subscription
  

flatMap

The flatmap is a operator is an operator in reactive programming particularly in Project Reactor and RxJava, that transforms each element emitted by a source publisher into new publisher then flattens these inner publisher instance into a single publisher and It allows asynchronous processing of each element and merges the result.

When to Use flatMap:

We use flatmap operator on publisher to handle the business means It can handle every event in the publisher. Below we provide the different situations to use flatmap operator in reactive programming.

• Asynchronous Processing: When you need to perform an asynchronous operation of each element like fetching data from a remote service for each item.
• Transforming Elements: When the transformation of elements involves producing multiple values or another reactive stream.
• Merging Results: When you need to merge the results of multiple asynchronous operations into single stream.

switchIfEmpty

The switchIfEmpty is a another operator in the reactive programming and It is used to provide an alternative sequence if the source like publisher completes without emitting any Items. It essentially “switches” to a fallback Publisher when the original Publisher is empty.

When to Use switchIfEmpty

• Default Values: When we need to provide a default value if the original publisher emits nothing.
• Fallback Mechanism: When you want to handle cases where no data is produced and ensure that the subscriber always receives some data.
• Graceful Degradation: When you want to gracefully degrade functionality by providing a fallback response when the primary data source is empty.

flatmap and switchifempty in Spring Reactive

Here, we provide examples for flatmap and switchIfEmpty operators with Mono and Flux publishers. Basically the switchIfEmpty is used when publisher emits nothing.

flatmap and switchIfEmpty with Mono publisher

In this example, we write a simple program to explain the flatmap and switchIfEmpty with Mono publisher. Below we provide the example for your reference.

package com.app;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import reactor.core.publisher.Mono;
@SpringBootApplication
public class PublishersApplication {
    public static void main(String[] args) {
        SpringApplication.run(PublishersApplication.class, args);
        Mono<String> msg = Mono.just("Hello Geeks");
        msg.flatMap(msgs -> {
            return Mono.just("Hello, " + msgs + "!");
        }).switchIfEmpty(Mono.just("No data available")).subscribe(System.out::println);
In the above program, first we create Mono publisher with String type and by using Mono.just(). 
We provide the data to the publisher after this we use flatmap on Mono object, and this flatmap return a publisher. 
Immediately on flatmap we use switchIfEmpty operator. If publisher is empty the switchIfEmpty returns the No data available message other wise It returns Hello, Hello Geeks!
Output:


flatmap and switchIfEmpty with Flux publisher
In this example, we write a simple program to explain the flatmap and switchIfEmpty with Flux publisher. Below we provide the example for your reference.
    
package com.app;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
@SpringBootApplication
public class PublishersApplication {
    public static void main(String[] args) {
        SpringApplication.run(PublishersApplication.class, args);
        Flux<String> names = Flux.just("John", "Marry", "Micky", "Hani");
        names.flatMap(name -> {
            return Mono.just("Hello, " + name + "!");
        }).switchIfEmpty(Mono.just("No names available")).subscribe(System.out::println);
In the above program, first we create Flux publisher with String type and by using Flux.just(). 
We provide the data to the publisher after this we use flatmap on Flux object, and this flatmap return a publisher. 
Immediately on flatmap we use switchIfEmpty operator. If publisher is empty the switchIfEmpty returns the No names available message and then prints each names to the console.
Output:


                
Spring Boot - Reactive Programming Using Spring Webflux Framework
                
In this article, we will explore React programming in Spring Boot, Reactive programming is an asynchronous, non-blocking programming paradigm for developing highly responsive applications that react to external stimuli. What is Reactive ProgrammingIn reactive programming, the flow of data is asynchronous through push-based publishers and subscriber
                
Spring Cloud Stream - Functional and Reactive
                
Spring Cloud Stream is a Spring framework that simplifies creating event-driven microservices. It uses functional programming constructs for message processing logic, often using annotated methods within a class and reactive programming tools like Reactor for asynchronous and reactive processing. Maven Dependencies&lt;dependency&gt; &lt;groupId&gt;
                
Testing Spring WebFlux Reactive CRUD Rest APIs Using WebTestClient
                
Spring Boot is one of the famous frameworks for Back-end development. The Spring Boot Community Developed the Spring Reactive Web Framework. This Reactive Framework is available from Spring Boot 5.0 and Above versions only. The Spring Reactive allows developers to build Asynchronous, Non-Blocking, and Event-Driven Web Applications. When compared wi
                
Spring WebFlux Reactive CRUD REST API Example
                
Spring WebFlux can be defined as the reactive programming framework provided by the Spring ecosystem for the building of asynchronous, non-blocking, and event-driven applications and it can be designed to handle a large number of concurrent connections while consuming less resources. Key Terminologies:Mono and Flux: Mono can represent the publisher
                
Router Functions in Spring Reactive
                
Spring Reactive programming is an asynchronous and non-blocking paradigm for developing highly responsive applications. It enables developers to build applications that handle high-load traffic without compromising performance. Spring WebFlux, a part of the Spring Framework, supports reactive programming with non-blocking, backpressure-enabled type
                
Building Reactive Microservices with Spring WebFlux
                
This article will teach us how to build reactive microservices with Spring WebFlux using a related example. Here, we create a student microservice to handle students and their data. For understanding purposes, we provide basic features and functionalities such as adding a student, searching for a student, deleting a student, and getting all student
                
Spring WebFlux Application Integration with Reactive Messaging System Kafka
                
Spring WebFlux is the framework for building reactive applications on the JVM. It is useful for reactive programming and makes it easier to build asynchronous, non-blocking and event-driven applications. Apache Kafka is a distributed streaming platform which allows us to publish and subscribe to streams of the records in a fault-tolerant way and pr
                
Reactive JWT Authentication Using Spring WebFlux
                
JSON Web Token (JWT) authentication is a popular method for securing APIs in microservices architectures. With Spring WebFlux, the reactive web framework, we can create highly scalable and responsive applications. In this article, we will guide you on how to implement JWT authentication in a reactive Spring WebFlux application. JWT is a compact and
                
Migrating a Spring Boot Application from Spring Security 5 to Spring Security 6
                
Spring Security is a powerful authentication and access control framework for Java applications specially for those built with the Spring Framework. With the release of Spring Security 6, several enhancements and changes have been introduced to simplify the security configuration and provide better performance and security features. This article ai
                
Monitoring and Logging for Reactive Applications
                
Reactive applications are designed to be responsive, resilient, elastic, and message-driven. Monitoring and logging are the crucial aspects of maintaining and troubleshooting these applications. They can provide insights into the application performance, help detect issues early, and ensure smooth operation. This article explores how to set up the
          
Company
About Us
Legal
In Media
Contact Us
Advertise with us
GFG Corporate Solution
Placement Training Program
GeeksforGeeks Community
Languages
Python
Java
C++
PHP
GoLang
SQL
R Language
Android Tutorial
Tutorials Archive
DSA
Data Structures
Algorithms
DSA for Beginners
Basic DSA Problems
DSA Roadmap
Top 100 DSA Interview Problems
DSA Roadmap by Sandeep Jain
All Cheat Sheets
Data Science & ML
Data Science With Python
Data Science For Beginner
Machine Learning Tutorial
ML Maths
Data Visualisation Tutorial
Pandas Tutorial
NumPy Tutorial
NLP Tutorial
Deep Learning Tutorial
Web Technologies
HTML
CSS
JavaScript
TypeScript
ReactJS
NextJS
Bootstrap
Web Design
Python Tutorial
Python Programming Examples
Python Projects
Python Tkinter
Web Scraping
OpenCV Tutorial
Python Interview Question
Django
Computer Science
Operating Systems
Computer Network
Database Management System
Software Engineering
Digital Logic Design
Engineering Maths
Software Development
Software Testing
DevOps
Git
Linux
AWS
Docker
Kubernetes
Azure
GCP
DevOps Roadmap
System Design
High Level Design
Low Level Design
UML Diagrams
Interview Guide
Design Patterns
OOAD
System Design Bootcamp
Interview Questions
Inteview Preparation
Competitive Programming
Top DS or Algo for CP
Company-Wise Recruitment Process
Company-Wise Preparation
Aptitude Preparation
Puzzles
School Subjects
Mathematics
Physics
Chemistry
Biology
Social Science
English Grammar
Commerce
World GK
GeeksforGeeks Videos
DSA
Python
Java
C++
Web Development
Data Science
CS Subjects
        
 
        We use cookies to ensure you have the best browsing experience on our website. By using our site, you
        acknowledge that you have read and understood our
        Cookie Policy &
        Privacy Policy
        Got It !
                    
Please go through our recently updated Improvement Guidelines before submitting any improvements.
                    
This improvement is locked by another user right now. You can suggest the changes for now and it will be under 'My Suggestions' Tab on Write.
                    
You will be notified via email once the article is available for improvement.
                        Thank you for your valuable feedback!
                        Suggest changes
                  
Please go through our recently updated Improvement Guidelines before submitting any improvements.
                      
Suggest Changes
                      
Help us improve. Share your suggestions to enhance the article. Contribute your expertise and make a difference in the GeeksforGeeks portal.