https://github.com/ghusta/spring-boot-demo-event-publishing

Demo for Spring Boot Application Events
https://github.com/ghusta/spring-boot-demo-event-publishing

event spring-boot

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Demo for Spring Boot Application Events

• Host: GitHub
• URL: https://github.com/ghusta/spring-boot-demo-event-publishing
• Owner: ghusta
• Created: 2023-03-15T21:00:07.000Z (over 3 years ago)
• Default Branch: main
• Last Pushed: 2023-06-02T18:53:48.000Z (about 3 years ago)
• Last Synced: 2025-02-24T13:48:41.045Z (over 1 year ago)
• Topics: event, spring-boot
• Language: Java
• Homepage:
• Size: 75.2 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 1
• Metadata Files:
  • Readme: README.adoc

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README

          
= Demo for Spring Boot Application Events

:author: Guillaume HUSTA

:toc:

== Overview

Demo for testing publish/subscribe events with Spring Boot.

Some subscribers are *synchronous*, others are *asynchronous* like email sending.

=== Publisher

One publisher publishes events.

All these events will be subclasses of `ObservationEvent`.

=== Subscribers

There are 2 kinds of subscribers : synchronous and asynchronous.

==== Synchronous

* `ObservationEventCyanLoggerListener` prints events on console with color _cyan_

* `ObservationEventGreenLoggerListener` prints events on console with color _green_

* `ObservationEventRedLoggerListener` prints events on console with color _red_

==== Asynchronous

* `AsyncObservationEventLoggerListener` prints events on console asynchronously

* `SendMailObservationListener` sends emails asynchronously, if SMTP server is available

== How to test it

=== Ensure a SMTP server is accessible

Either configure `src/main/resources/application.properties` with your own SMTP server (see https://docs.spring.io/spring-boot/docs/current/reference/html/application-properties.html#appendix.application-properties.mail[Spring Boot mail configuration]), or launch a fake SMTP server.

You can do the latter with the provided link:docker-compose.yml[docker-compose.yml] file, launching a SMTP server by default on localhost, port 2525 :

[source,bash]

----

docker compose up -d

----

The sent emails will then be accessible in the local folder `sent-emails`.

=== Launch Spring Boot app

With Maven :

[source,bash]

----

mvn spring-boot:run

----

=== Execution log example

====

[%hardbreaks]

2023-03-16T10:22:19.486+01:00  INFO 6240 --- [           main] c.e.d.DemoEventPublishingApplication     : Starting DemoEventPublishingApplication using Java 17.0.6 with PID 6240 (\Java\demo-event-publishing\target\classes started by g in \Java\demo-event-publishing)

2023-03-16T10:22:19.489+01:00  INFO 6240 --- [           main] c.e.d.DemoEventPublishingApplication     : No active profile set, falling back to 1 default profile: "default"

2023-03-16T10:22:19.868+01:00  INFO 6240 --- [           main] c.e.d.DemoEventPublishingApplication     : Started DemoEventPublishingApplication in 0.619 seconds (process running for 0.825)

2023-03-16T10:22:19.870+01:00  INFO 6240 --- [           main] c.e.d.DemoEventPublishingApplication     : Running the app...

2023-03-16T10:22:19.870+01:00  INFO 6240 --- [           main] c.e.d.service.MyService                  : Entering addObservation()...

ASYNC -- It's a ObservationAddedEvent !

[blue]#It's a ObservationAddedEvent... Content is : Nothing interesting 😴#

[green]#It's a ObservationAddedEvent... Content is : Nothing interesting 😴#

[red]#It's a ObservationAddedEvent... Content is : Nothing interesting 😴#

2023-03-16T10:22:19.885+01:00  INFO 6240 --- [           main] c.e.d.service.MyService                  : Entering publishObservation()...

ASYNC -- It's a ObservationPublishedEvent !

[blue]#It's a ObservationPublishedEvent !#

[green]#It's a ObservationPublishedEvent !#

[red]#It's a ObservationPublishedEvent !#

2023-03-16T10:22:19.886+01:00  INFO 6240 --- [           main] c.e.d.service.MyService                  : Entering removeObservation()...

2023-03-16T10:22:19.886+01:00 DEBUG 6240 --- [         task-4] c.e.d.l.SendMailObservationListener      : Sending a mail async... (Observation published) (in task-4)

2023-03-16T10:22:19.885+01:00 DEBUG 6240 --- [         task-2] c.e.d.l.SendMailObservationListener      : Sending a mail async... (Observation added) (in task-2)

[blue]#It's a ObservationRemovedEvent !#

[green]#It's a ObservationRemovedEvent !#

[red]#It's a ObservationRemovedEvent !#

2023-03-16T10:22:19.887+01:00 DEBUG 6240 --- [         task-6] c.e.d.l.SendMailObservationListener      : Event not managed (com.example.demoeventpublishing.event.ObservationRemovedEvent)

2023-03-16T10:22:20.014+01:00 DEBUG 6240 --- [         task-4] c.e.d.l.SendMailObservationListener      : Mail sent (in task-4)

2023-03-16T10:22:20.015+01:00 DEBUG 6240 --- [         task-2] c.e.d.l.SendMailObservationListener      : Mail sent (in task-2)

====

== References

* Spring Boot :

** https://docs.spring.io/spring-boot/docs/current/reference/html/features.html#features.spring-application.application-events-and-listeners[Application Events and Listeners]

** https://docs.spring.io/spring-boot/docs/current/reference/html/io.html#io.email[Sending Email]

** https://docs.spring.io/spring-boot/docs/current/reference/html/features.html#features.task-execution-and-scheduling[Task Execution and Scheduling], for asynchronous task execution (`@EnableAsync`)

* Articles :

** https://reflectoring.io/spring-boot-application-events-explained/[Spring Boot Application Events Explained]

** https://howtodoinjava.com/spring-core/how-to-publish-and-listen-application-events-in-spring/[Spring Application Events]

* Issues / Mentions :

** ⭐ https://github.com/spring-projects/spring-framework/issues/27777[Mention explicitly that @EventListener should be put on public methods] => *INVALID*

*** Related : https://github.com/spring-projects/spring-framework/pull/26785