Spring Boot Application with Two Entrypoints: CLI and Web Service

Question

I have a spring-boot-starter application that I created that started as a CommandLineRunner that runs in Kubernetes as a CronJob, something like:

@SpringBootApplication
@EnableAutoConfiguration
public class JobApplication implements CommandLineRunner {
  Logger logger = LoggerFactory.getLogger(JobApplication.class);


  public static void main(String[] args) {
    ConfigurableApplicationContext context = SpringApplication.run(JobApplication.class, args);
    context.close();
  }

  @Override
  public void run(String... args) throws Exception {
    // run the job
  }
}

I currently run the application in a Dockerfile like this and everything works fine.

CMD java -jar /job/job.jar

In this Application there's some Database code and DTOs that I'd like to use and expose as a Spring Web Service, ideally inside the same codebase so I don't have to create multiple Github repos and Java projects and publish a shared library that both use. I'd like to keep it simple and just be able to compile and use them directly.

Is there a way to do that? I think I'd need a second WebApplication class, but then I'm not sure how to execute it so it uses that instead of the Job.

If not, is there a recommended approach to do what I want to do (building multiple jars is ok if that's the only way... but I'd really like to keep all the code in the same project)?

Answer 1

Have you tried to try to use @Profile ?

For example:

@Profile("CMD")
@SpringBootApplication
@EnableAutoConfiguration
public class JobApplication implements CommandLineRunner {
  Logger logger = LoggerFactory.getLogger(JobApplication.class);


  public static void main(String[] args) {
    ConfigurableApplicationContext context = SpringApplication.run(JobApplication.class, args);
    context.close();
  }

  @Override
  public void run(String... args) throws Exception {
    // run the job
  }
}


@Profile("WEB")
@SpringBootApplication
public class WebApplication extends SpringBootServletInitializer {

    public static void main(String[] args) {
        SpringApplication.run(WebApplication.class, args);
    }

}

You can start command line as java -jar /job/job.jar -Dspring.profiles.active=CMD

and web with profile WEB.

Because @Profile is a runtime spring annotation it can't be processed until spring context is loaded, you will have (as you discovered)

Unable to find a single main class from the following candidates [my.app.WebApplication, my.app.JobApplication]

For this reason you can start a specific spring boot main class with

-Dstart-class=com.sample.WebApplication

And now it should not load the second because now the @Profile should work