java - Spring Boot shutdown hook

Question

How can I register/add a custom shutdown routine that shall fire when my Spring Boot application shuts down?

Scenario: I deploy my Spring Boot application to a Jetty servlet container (i.e., no embedded Jetty). My application uses Logback for logging, and I want to change logging levels during runtime using Logback's MBean JMX configurator. Its documentation states that to avoid memory leaks, on shutdown a specific LoggerContext shutdown method has to be called.

What are good ways to listen on Spring Boot shutdown events?

I have tried:

public static void main(String[] args) throws Exception {
    ConfigurableApplicationContext cac = SpringApplication.run(Example.class, args);

    cac.addApplicationListener(new ApplicationListener<ContextClosedEvent>() {

        @Override
        public void onApplicationEvent(ContextClosedEvent event) {
            logger.info("Do something");
        }
    });
}

but this registered listener does not get called when the application shuts down.

Answer 1

https://docs.spring.io/spring-boot/docs/current-SNAPSHOT/reference/htmlsingle/#features.spring-application.application-exit

Each SpringApplication will register a shutdown hook with the JVM to ensure that the ApplicationContext is closed gracefully on exit. All the standard Spring lifecycle callbacks (such as the DisposableBean interface, or the @PreDestroy annotation) can be used.

In addition, beans may implement the org.springframework.boot.ExitCodeGenerator interface if they wish to return a specific exit code when the application ends.