Configure an object provided by a Guice Module

Question

I have a Module that provides a JDBI DBI instance like this:

@Provides
@Singleton
DBI dbi(DataSource dataSource) { return new DBI(dataS         


        

Answer 1

The Guice Injections documentation describes how to invoke an instance method by annotating the method with @Inject.

It doesn't mention that the instance can be a Guice module. As such, you can do this:

class MyConfigurationModule extends AbstractModule {
  @Override
  protected void configure() {
    requestInjection(this);
  }

  @Inject
  void configureDbi(DBI dbi) {
    // Do whatever configuration.
  }  
}

Answer 2

Guice is designed to have many different modules for different purposes. This allows you to swap settings and other injections while leaving others the same.

So you could do something like the following:

• Create an annotation for your application to use with your DBI dependency injection:

Example:

import com.google.inject.BindingAnnotation;
import java.lang.annotation.Target;
import java.lang.annotation.Retention;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;

@BindingAnnotation @Target({ FIELD, PARAMETER, METHOD }) @Retention(RUNTIME)
public @interface ApplicationDBI {}

• Create a second module for DBI specific to your application.

Example:

@Provides @ApplicationDBI
// Choose the appropriate scope here
protected DBI provideConfiguredDBI(DBI baseDBI) {
    // configure the baseDBI here
    return baseDBI;
}

• Annotate the application injection with your new annotation

Example:

public class DatabaseWrapper {
    private final DBI dbi;
    @Inject
    DatabaseWrapper(@ApplicationDBI DBI dbi) {
        this.dbi = dbi;
    }
}

Then in your main method:

Injector inj = Guice.createInjector(new DatabaseModule(),
                 new ApplicationDBIModule(),
                 ...);