Spring Boot - Reactive Programming Using Spring Webflux Framework

Last Updated : 28 Apr, 2025

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 Programming

In reactive programming, the flow of data is asynchronous through push-based publishers and subscribers instead of synchronous pull-based calls.
The core abstraction in reactive programming is the reactive stream which provides a standard way to work with asynchronous streams of data. The two primary reactive stream interfaces are Publisher and Subscriber.
Publishers push data to Subscribers asynchronously. Subscribers register callbacks and are notified when new data arrives instead of actively polling for it.
Examples of reactive streams include Mono and Flux in Spring Webflux. Mono represents a single event/value and Flux represents a stream of multiple values.

Benefits of Reactive Programming with Spring Webflux

Support for Reactive Types
Integration with Reactive Streams
Non-blocking I/O
Microservices-friendly

Spring Webflux Dependency

Gradle:

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-webflux'
}

Maven:

<!-- https://mvnrepository.com/artifact/org.springframework/spring-webflux -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-webflux</artifactId>
    <version>6.1.3</version>
</dependency>

Reactive Types in Spring Webflux

Mono: Mono specifically represents a single value or no value at all
Flux: Flux represents a **stream of zero or more elements** emitted over time

Step By Step Implementation

Step 1: Set up a new Spring MVC project

Create a new Maven project in your preferred IDE (e.g., IntelliJ or Eclipse or Spring Tool Suite) and add the following dependencies.

Spring Webflux
Mongo Db - for Database
Lombok

XML

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>3.2.2</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>REST_Spring_Flux</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>REST_Spring_Flux</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>17</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-mongodb-reactive</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-webflux</artifactId>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>io.projectreactor</groupId>
            <artifactId>reactor-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

Project Structure:

Directory Structure

Step 2: Configure Mongo Db Database

# MongoDB properties
spring.data.mongodb.host=localhost
spring.data.mongodb.port=27017
spring.data.mongodb.database=student_management

host: host property pecifies the hostname or IP address of the MongoDB server. In this example we are using localhost.
port: property defines the port number on which the MongoDB server is running. In this example we are running our server on port no : 27010 [8080].
database: sets the name of the MongoDB database that our Spring Boot application will connect to. In this example, the database name is "student_management".

Step 3: Create Model Class

Student.class File:

Java

package com.example.demo.entities;

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;

@Document
public class Student {
    @Id private String id;
    private String name;
    private int age;

    public Student(String id, String name, int age)
    {
        super();
        this.id = id;
        this.name = name;
        this.age = age;
    }

    public Student()
    {
        super();
        // TODO Auto-generated constructor stub
    }

    public String getId() { return id; }

    public void setId(String id) { this.id = id; }

    public String getName() { return name; }

    public void setName(String name) { this.name = name; }

    public int getAge() { return age; }

    public void setAge(int age) { this.age = age; }
}

Note: @Document annotation indicate that this class should be mapped to a MongoDB document.

Step 4: Create Repository Interface

StudentRepository.class File:

Java

package com.example.demo.repositories;

import com.example.demo.entities.*;
import org.springframework.data.mongodb.repository.ReactiveMongoRepository;

public interface StudentRepository
    extends ReactiveMongoRepository<Student, String> {
}

Step 5: Create Controller

StudentController.class File:

Java

package com.example.demo.controller;

import com.example.demo.entities.Student;
import com.example.demo.services.StudentService;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

@RestController
@RequestMapping("/api/students")
public class StudentController {

    private final StudentService studentService;

    public StudentController(StudentService studentService)
    {
        this.studentService = studentService;
    }

    public Mono<Student>
    saveStudent(@RequestBody Student student)
    {
        return studentService.saveStudent(student);
    }

    @GetMapping public Flux<Student> getAllStudents()
    {
        return studentService.getAllStudents();
    }

    @GetMapping("/{id}")
    public Mono<Student>
    getStudentById(@PathVariable String id)
    {
        return studentService.getStudentById(id);
    }
    @PostMapping
    public Mono<Student>
    createStudent(@RequestBody Student student)
    {
        return studentService.saveStudent(student);
    }

    @DeleteMapping("/{id}")
    public Mono<Void> deleteStudent(@PathVariable String id)
    {
        return studentService.deleteStudent(id);
    }
}

Step 6: Create Service Interface

StudentService.class File:

Java

package com.example.demo.services;
import com.example.demo.entities.*;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

public interface StudentService {
    Mono<Student> saveStudent(Student student);
    Flux<Student> getAllStudents();
    Mono<Student> getStudentById(String id);
    Mono<Void> deleteStudent(String id);
}

Step 7: Create ServiceImpl

StudentServiceImpl.class File:

Java

package com.example.demo.services;

import com.example.demo.entities.*;
import com.example.demo.repositories.StudentRepository;
import org.springframework.stereotype.Service;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

@Service
public class StudentServiceImpl implements StudentService {

    private final StudentRepository studentRepository;

    public StudentServiceImpl(
        StudentRepository studentRepository)
    {
        this.studentRepository = studentRepository;
    }

    @Override
    public Mono<Student> saveStudent(Student student)
    {
        return studentRepository.save(student);
    }

    @Override public Flux<Student> getAllStudents()
    {
        return studentRepository.findAll();
    }

    @Override public Mono<Student> getStudentById(String id)
    {
        return studentRepository.findById(id);
    }

    @Override public Mono<Void> deleteStudent(String id)
    {
        return studentRepository.deleteById(id);
    }
}

Step 8: Run the Application

Now, You can run the Spring Boot application from IDE or by using the command-line tool provided by Spring Boot.

mvn spring-boot:run

Step 9: Test the Endpoints Using Postman

POST: http://localhost:8080/api/students-- Post the student data
GET: http://localhost:8080/api/students-- Get all student details
GET: http://localhost:8080/api/students/{id} -- Get the student details by Id

Output:

Spring Boot - Reactive Programming Using Spring Webflux Framework

pranay0911

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Article Tags :

Spring Boot - Reactive Programming Using Spring Webflux Framework

What is Reactive Programming

Benefits of Reactive Programming with Spring Webflux

Spring Webflux Dependency

Gradle:

Maven:

Reactive Types in Spring Webflux

Step By Step Implementation

Step 1: Set up a new Spring MVC project

Project Structure:

Step 2: Configure Mongo Db Database

Step 3: Create Model Class

Student.class File:

Step 4: Create Repository Interface

StudentRepository.class File:

Step 5: Create Controller

StudentController.class File:

Step 6: Create Service Interface

StudentService.class File:

Step 7: Create ServiceImpl

StudentServiceImpl.class File:

Step 8: Run the Application

Step 9: Test the Endpoints Using Postman

Output:

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