Spring Boot Event Listener Example (2024)

In this tutorial, we'll demonstrate how to use @EventListener in Spring Boot.

Q: What is Spring Boot event listeners?
Ans:

Annotation for Spring Boot event listeners A method that listens for spring boot events is created using @EventListener. The ApplicationEventPublisher class is used to broadcast a spring boot event. When an event is published with the ApplicationEventPublisher class, the @EventListener annotated methods are called.

A listener can be defined in two ways. Either the @EventListener annotation or the ApplicationListener interface can be used.

Q: What is listener in event handling?
Ans:

When an event occurs, a listener object is notified.

Q: Is it possible to have Publisher in one Spring Boot application and Listener in another application?
Ans:

Publisher and Listener of the EventListener can be handle within only one Spring application. We'll need to use an external message queue to spread them over the network (e.g. Kafka, RabbitMQ).

Create Spring Boot application

Create Spring Boot application from Spring Initializr.

Project Structure

Add Dependencies

Add spring-boot-starter-web dependency in pom.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>2.6.7</version>
		<relativePath/> <!-- lookup parent from repository -->
	</parent>
	<groupId>com.techgeeknext</groupId>
	<artifactId>SpringBootEventListener</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<name>SpringBootEventListener</name>
	<description>Spring Boot Event Listener Example</description>
	<properties>
		<java.version>1.8</java.version>
	</properties>
	<dependencies>
		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-web</artifactId>
		</dependency>

		<dependency>
			<groupId>org.springframework.boot</groupId>
			<artifactId>spring-boot-starter-test</artifactId>
			<scope>test</scope>
		</dependency>
	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.springframework.boot</groupId>
				<artifactId>spring-boot-maven-plugin</artifactId>
			</plugin>
		</plugins>
	</build>

</project>

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Spring Boot Event Publisher

The ApplicationEventPublisher is used to broadcast a spring boot event. When an event is published with the ApplicationEventPublisher, the @EventListener annotated methods are called.
Create two publishing methods, one for the Email Event object and the other for the String message.

package com.techgeeknext.publisher;

import com.techgeeknext.event.EmailEvent;
import org.springframework.context.ApplicationEventPublisher;
import org.springframework.stereotype.Component;

@Component
public class EmailPublisher {

    private final ApplicationEventPublisher eventPublisher;

    EmailPublisher(ApplicationEventPublisher publisher) {
        this.eventPublisher = publisher;
    }

    public void publishEmailEvent(EmailEvent event) {
        eventPublisher.publishEvent(event);
    }

    public void publishMsgEvent(String msg) {
        eventPublisher.publishEvent(msg);
    }
}