How to prevent Spring Boot daemon/server applicati

问题:

My Spring Boot application is not a web server, but it's a server using custom protocol (using Camel in this case).

But Spring Boot immediately stops (gracefully) after started. How do I prevent this?

I'd like the app to stop if Ctrl+C or programmatically.

@CompileStatic
@Configuration
class CamelConfig {

    @Bean
    CamelContextFactoryBean camelContext() {
        final camelContextFactory = new CamelContextFactoryBean()
        camelContextFactory.id = 'camelContext'
        camelContextFactory
    }

}

回答1:

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.

回答2:

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()
    }
}

回答3:

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>

回答4:

Spring Boot leaves the task of running the application to the protocol around which the application is implemented. See, for example, this guide:

Also required are some housekeeping objects like a CountDownLatch to keep the main thread alive...

So the way of running a Camel service, for example, would to be to run Camel as a standalone application from your main Spring Boot application class.

回答5:

My project is NON WEB Spirng Boot. My elegant solution is create a daemon thread by CommandLineRunner. Then, Application do not shutdown immediately.

 @Bean
    public CommandLineRunner deQueue() {
        return args -> {
            Thread daemonThread;
            consumer.connect(3);
            daemonThread = new Thread(() -> {`enter code here`
                try {
                    consumer.work();
                } catch (InterruptedException e) {
                    logger.info("daemon thread is interrupted", e);
                }
            });
            daemonThread.setDaemon(true);
            daemonThread.start();
        };
    }

回答6:

To keep the java process alive when not deploying a web application set the webEnvironment property to false like so:

 SpringApplication sa = new SpringApplication();
 sa.setWebEnvironment(false); //important
 ApplicationContext ctx = sa.run(ApplicationMain.class, args);

回答7:

for springboot app to run continously it has to be run in a container, otherwise it is just like any java app all threads are done it finishes, you can add

<dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

and it will turn it into webapp, if not you are responsible keeping it alive in your implementation