Google Guice and varying injections at runtime

问题

I'd like to vary the injected implementations based on something that's not known until runtime. Specifically, I'd like my app to operate as different versions where the "version" is not determined until a request is executing. Also, the "version" could vary per request.

After reading the docs it seems that I could implement a providers in cases where I need to choose an implementation at runtime based on the "version". Additionally, I could roll my own on top of juice.

Is implementing a provider the best way to go in this scenario? I'd like to know if there is a best practice or if anyone else out there has tried to use Guice to tackle this problem.

Thanks for any help!

-Joe

回答1:

I think that if the version can be known only at runtime, you must provide the versioned "services" manually with custom provider. Possibly something like this:

@Singleton
public abstract class VersionedProvider<T, V> {

    private Map<V, T> objects;

    T get(V version) {
        if (!objects.containsKey(version)) {
            objects.put(version, generateVersioned(version));
        }
        return objects.get(version);
    }

    // Here everything must be done manually or use some injected
    // implementations
    public abstract T generateVersioned(V version);
}

回答2:

public class MyRuntimeServiceModule extends AbstractModule {
  private final String runTimeOption;

  public ServiceModule(String runTimeOption) {
    this.runTimeOption = runTimeOption;
  }

  @Override protected void configure() {

    Class<? extends Service> serviceType = option.equals("aServiceType") ?
        AServiceImplementation.class : AnotherServiceImplementation.class;
    bind(Service.class).to(serviceType);
  }
}

  public static void main(String[] args) {
  String option = args[0];
  Injector injector = Guice.createInjector(new MyRuntimeServiceModule(option));

}

来源：https://stackoverflow.com/questions/7651980/google-guice-and-varying-injections-at-runtime