How to prevent Spring Boot daemon/server application from closing/shutting down immediately?

I found the solution, using org.springframework.boot.CommandLineRunner + Thread.currentThread().join(), e.g.: (note: code below is in Groovy, not Java)

package id.ac.itb.lumen.social

import org.slf4j.LoggerFactory
import org.springframework.boot.CommandLineRunner
import org.springframework.boot.SpringApplication
import org.springframework.boot.autoconfigure.SpringBootApplication

@SpringBootApplication
class LumenSocialApplication implements CommandLineRunner {

    private static final log = LoggerFactory.getLogger(LumenSocialApplication.class)

    static void main(String[] args) {
        SpringApplication.run LumenSocialApplication, args
    }

    @Override
    void run(String... args) throws Exception {
        log.info('Joining thread, you can press Ctrl+C to shutdown application')
        Thread.currentThread().join()
    }
}

As of Apache Camel 2.17 there is a cleaner answer. To quote http://camel.apache.org/spring-boot.html:

To keep the main thread blocked so that Camel stays up, either include the spring-boot-starter-web dependency, or add camel.springboot.main-run-controller=true to your application.properties or application.yml file.

You will want the following dependency too:

<dependency> <groupId>org.apache.camel</groupId> <artifactId>camel-spring-boot-starter</artifactId> <version>2.17.0</version> </dependency>

Clearly replace <version>2.17.0</version> or use the camel BOM to import dependency-management information for consistency.

An example implementation using a CountDownLatch:

@Bean
public CountDownLatch closeLatch() {
    return new CountDownLatch(1);
}

public static void main(String... args) throws InterruptedException {
    ApplicationContext ctx = SpringApplication.run(MyApp.class, args);  

    final CountDownLatch closeLatch = ctx.getBean(CountDownLatch.class);
    Runtime.getRuntime().addShutdownHook(new Thread() {
        @Override
        public void run() {
            closeLatch.countDown();
        }
    });
    closeLatch.await();
}

Now to stop your application, you can look up the process ID and issue a kill command from the console:

kill <PID>