How to provide a parameterized component in Spring?

mike :

Currently, I have a component that implements CommandLineRunner and parses the command line arguments with Commons CLI.

java -jar app.jar --host 123.123.222 --port 8080

There is also another component, Requester, which depends on (a subset of) those arguments.

@Component
public class Requester
{

  // host and port need to be configured once
  private final String host;
  private final int port;

  public Requester(String host, int port)
  {
    this.host = host;
    this.port = port;
  }

  public boolean doRequest(String name) throws Exception
  {
    String url = "http://" + host + ":" + port + "/?command=" + name;

    URL obj = new URL(url);
    HttpURLConnection connection = (HttpURLConnection) obj.openConnection();
    int responseCode = connection.getResponseCode();
    return 200 == responseCode;
  }

}

What can I do to autowire a configured Requester into future components? What is the Spring way to create parameterized, singleton beans?

---

One solution would be to have every component, that has any dependency on the program arguments, implement CommandLineRunner. This way it could parse the program arguments itself, but that is a highly redundant approach. There must be a better solution.

mike :

Inspired by JB Nizet's comment, I now parse the command line arguments and register the beans manually before I start the Spring application.

I identified two ways: provide the c'tor arguments and let Spring create the beans or provide a supplier function to Spring.

Now it's possible to declare @Autowire private Requester requester; in other parts of the application.

---

In order for this solution to work the @Component annotation needs to be removed from Requester, because otherwise problems may occur when Spring can't provide the necessary constructor arguments.

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        // parse args here
        String host = getHost();
        int port = getPort();

        SpringApplication application = new SpringApplication(Application.class);

        // provide c'tor arguments and let Spring create the instance
        BeanDefinitionCustomizer bdc = bd -> {
            // working with bd.getPropertyValues() uses setter instead of c'tor
            ConstructorArgumentValues values = bd.getConstructorArgumentValues();
            values.addIndexedArgumentValue(0, host);
            values.addIndexedArgumentValue(1, port);
        };
        application.addInitializers((GenericApplicationContext ctx) -> ctx.registerBean(Requester.class, bdc));

        // or create the instance yourself
        Requester requester = new Requester(host, port);
        application.addInitializers((GenericApplicationContext ctx) -> ctx.registerBean(Requester.class, () -> requester));
        application.run(args);
    }

}