Question

I have some sample code which is using factories. I’d like to clean up the code by removing the factories and use Guice instead. I attempted to do this but I hit a small roadblock. I am really new to Guice, so I am hoping someone can help me out here.

Existing client code (Using factories):

public class MailClient {

    public static void main(String[] args) {
        MailConfig config = MailConfigFactory.get();
        config.setHost("smtp.gmail.com");
        Mail mail = MailFactory.get(config);
        mail.send();
    }
}

My attempt to refactor using Guice:

//Replaces existing factories
public class MailModule extends AbstractModule {

    @Override
    protected void configure() {
        bind(Mail.class)
        .to(MailImpl.class);

        bind(MailConfig.class)
        .to(MailConfigImpl.class);
    }
}

public class MailImpl implements Mail {

    private final MailConfig config;

    @Inject
    public MailImpl(MailConfig config) {
        this.config = config;
    }

    public void send() { ... }
}

public class MailClient {

    public static void main(String[] args) {
        MailModule mailModule = new MailModule();
        Injector injector = Guice.createInjector(mailModule);
        MailConfig config = injector.getInstance(MailConfig.class);
        config.setHost("smtp.gmail.com");
        Mail mail = //??
        mail.send();
     }
}

How would I construct an instance of MailImpl using the object config in my revised MailClient? Should I be using Guice in this way?

Answer 1

Take a look at AssistedInject. It appears to address this problem.