Nested configuration interfaces (#129)

[ketan]

This is only an initial draft to get feedback (please don't shoot me :)

This works by doing 2 things -

• a converter that checks if the target type is an
  implementation of the Config interface. If it is, then
  any further conversion is handed off to ConfigFactory with a
  (configurable)namespace prefix.
• The properties manager, that looks up @Source annotation
  will lookup the annotation on all interfaces.

Usage -

app.db.username =
app.db.password =

app.jetty.host =
app.jetty.port =

@Config.Sources({"/etc/app.properties"})
public interface BaseConfig extends Accessible {
}

public interface AppConfig extends BaseConfig {
   @DefaultValue("app.db")
    Database db();

    @DefaultValue("app.jetty")
    Jetty jetty();
}

public interface Database extends Accessible {
    @Key("${ns}.username")
    String host();

    @Key("${ns}.password")
    String password();
}

public interface Jetty extends Accessible {
    @Key("${ns}.host")
    String host();

    @Key("${ns}.port")
    int port();
}

[lviggiano]

Hi @ketan,

I like your pull request. Can you add some unit tests?

[lviggiano]

The problem here, is that every time this call is done, a new object (a dynamic proxy) is created; but that's also consistent with the rest of the code. Maybe we can add a class level annotation that allows owner to use a cached instance (see org.aeonbits.owner.ConfigCache.java, http://owner.aeonbits.org/docs/singleton/)

[AarjavP]

I would like to see this feature get added as well, is there anything I can do to help?

[ketan]

Unfortunately I've not had time to look at this PR, I don't think the situation will change anytime sokn., If someone wants to pick up this PR and make improvements, I'm happy...

[shakedel]

I might give it a go. What improvements were you thinking of?