Why there's no configuration file at all for dependency injection with Google Guice?

Question

I am checking out Google Guice as DI framework but I am a bit puzzled: why there\'s no configuration file at all?

I found a partial explanation on this question but it i

Answer 1

It is trivial to introduce boostrapping using configuration files if you are so inclined. We use Guice together with a simple API that loads property files where the things go that really need to be parameterized. This can be used together with @Named annotations and such, and of course you can have some conditionals in modules (though it is a good idea not to over-do that).

This is an example of how part of our bootstrapping is set up:

public class MetModules extends AbstractModule {

    private static final Logger log = LoggerFactory.getLogger(MetModules.class);

    private final Settings settings;

    public MetModules(Settings settings) {
        this.settings = settings;
    }

    @Override
    protected void configure() {

        // common (stage independent modules) go here
        install(new CommandsModule());
        install(new ServletsModule());
        install(new DataBaseModule(settings));
        install(new JobsModule(settings));

        // any development/ production specific modules
        Stage stage = currentStage();
        if (Stage.DEVELOPMENT.equals(stage)) {
            configureForDevelopment();
        } else { // PRODUCTION
            configureForProduction();
        }
    }

    /**
     * Install modules that will be used in development.
     */
    private void configureForDevelopment() {

        // Mock implementation of email delivery that just logs it got a
        // message rather than trying to send it.
        install(new AbstractModule() {
            @Override
            protected void configure() {
                bind(Delivery.class).toInstance(new Delivery() {

                    public String deliver(MailMessageExchange exchange)
                            throws DeliveryException {
                        log.info("email message: "
                                + exchange.getMessage().getMailMessage()
                                + " to "
                                + Arrays.asList(exchange.getMessage()
                                        .getMailMessage().getTo())
                                + " (not sent)");
                        return "fooMessageId";
                    }
                });
            }
        });

        // local in-memory registry suffices
        install(new LocalServiceRegistryModule());

        // local in memory db implementations of services
        install(new LocalServicesModule());
    }

    /**
     * Install modules that will be used in production.
     */
    private void configureForProduction() {
        // we really only need this (error interception and audit logging)
        // in production
        install(new AopModule());
        install(new ZooKeeperServiceRegistryModule());      }
}

Where Settings is what reads our properties files and such. Right now development/ production together with specific settings overrides specific for deployments seems to do the job for us, but we could go further with this if we wanted to obviously.