How to Return an Exit Code from a CommandLine Application in Spring Boot

How can I return an exit code from a CommandLine application in Spring Boot?

@SpringBootApplication
public class MyApp implements CommandLineRunner {

    public static void main(String[] args) {
        SpringApplication app = new SpringApplication(MyApp.class);
        System.exit(app.run(args).getExitCode());
    }

    @Override
    public void run(String... args) throws Exception {
        // Your application logic
        if (someCondition) {
            System.exit(1); // indicating an error
        } else {
            System.exit(0); // indicating success
        }
    }
}

Returning an exit code from a Spring Boot CommandLine application is essential for communicating the application's success or failure to the operating system. This can be done by leveraging the SpringApplication class and the CommandLineRunner interface effectively.

@SpringBootApplication
public class MyApp implements CommandLineRunner {
    public static void main(String[] args) {
        SpringApplication app = new SpringApplication(MyApp.class);
        System.exit(app.run(args).getExitCode());
    }

    @Override
    public void run(String... args) {
        System.out.println("Application started!");
        if (args.length == 0) {
            System.exit(1); // Exit with error if no args
        }
        System.exit(0); // Exit successfully
    }
}

Causes

• Improper exit code returns due to missing System.exit() calls.
• Not using CommandLineRunner to execute application logic.
• Misconfigured SpringApplication settings.

Solutions

• Utilize the CommandLineRunner interface to define application logic and gracefully return exit codes.
• Directly call System.exit() with the appropriate code based on application logic, indicating success or failure.
• Override the main method in your Spring Boot application to get the exit code from the application context.

Mistake: Failing to return an exit code after application logic execution.

Solution: Always ensure to call System.exit() with the relevant exit code when your application finishes execution.

Mistake: Using default Spring Boot application run method.

Solution: Override the run method to implement your command line logic and return proper exit codes.