In a Spring-Boot application without web server, what is the correct way to keep it running?

Question

I have written a small spring-boot application without embedded servers. It is intended to run from command line and stay running until the VM gets signalled. What is the intended way of in the spring-boot framework (v2.0) to keep the application alive as a service? Should I have a Thread.currentThread().wait(); as last statement in my run(ApplicationArguments args) method? Is there an enabling annotation?

Plainsong

Possible duplicate of How to prevent Spring Boot daemon/server application from closing/shutting down immediately? – Chromomere

it indeed looks duplicate, but not conclusive, and likely outdated. Most hints look very hacky. – Plainsong

System.in.read would block until the first key stroke... I want the thing just wait for Crtl-C. – Plainsong

@Plainsong the solultion given in this answer seems the right approach https://mcmap.net/q/467094/-how-to-prevent-spring-boot-daemon-server-application-from-closing-shutting-down-immediately better than waiting for a key stroke – Platonic

@Platonic That approach is bad as it will also work on all SpringBootTest tests. Hence those tests won't stop. – Jaimie

The solution with adding an empty scheduled task seems the least hacky one. @Scheduled(fixedDelay = Long.MAX_VALUE) public void doNotShutdown() {} It even works with the most basic Spring Boot Starter. – Jaimie

@SvenDöring you are right about that but if you are doing Unit Test without SpringBootTest this work. Enabling Scheduling is an idea. I didn't check but maybe since 2018 they are new solutions. – Platonic

Answer 1

from org.springframework.boot.web.embedded.netty.NettyWebServer, Official.

    private void startDaemonAwaitThread(DisposableServer disposableServer) {
        Thread awaitThread = new Thread("server") {

            @Override
            public void run() {
                disposableServer.onDispose().block();
            }

        };
        awaitThread.setContextClassLoader(getClass().getClassLoader());
        awaitThread.setDaemon(false);
        awaitThread.start();
    }

Orlon

that kind of contradicts the question condition of having a Spring-Boot application without a webserver, doesn't it? – Plainsong

I just assume there is another server instead of default web server, so it is necessary to keep application running. Refer to the official implementation, you can start a thread which blocked and waiting your server close. – Orlon