Suppose I have a value for which I have a default, which can be overridden if System.getProperty("foo") is set. I have one module for which I have

bindConstant().annotatedWith(Names.named("Default foo")).to(defaultValue);

I'm wondering what the best way of implementing a module for which I want to bind something annotated with "foo" to System.getProperty("foo"), or, if it does not exist, the "Default foo" binding.

I've thought of a simple module like so:

public class SimpleIfBlockModule extends AbstractModule {
    @Override
    public void configure() {
        requireBinding(Key.get(String.class, Names.named("Default foo")));
        if (System.getProperties().containsKey("foo")) {
            bindConstant().annotatedWith(Names.named("foo")).to(System.getProperty("foo"));
        } else {
            bind(String.class).annotatedWith(Names.named("foo")).to(Key.get(String.class, Names.named("Default foo")));
        }
    }
}

I've also considered creating a "system property module" like so:

public class SystemPropertyModule extends PrivateModule {
    @Override
    public void configure() {
        Names.bindProperties(binder(), System.getProperties());
        if (System.getProperties().contains("foo")) {
            expose(String.class).annotatedWith(Names.named("foo"));
        }
    }
}

And using SystemPropertyModule to create an injector that a third module, which does the binding of "foo". Both of these seem to have their downsides, so I'm wondering if there is anything I should be doing differently. I was hoping for something that's both injector-free and reasonably generalizable to multiple "foo" attributes. Any ideas?