CODEWITHSUNDEEP
dependency-injectionsingletonguice
Snekse
Snekse

Reputation: 15799

Getting an instance within a Guice Module

I have this class:

public class CompositeSecurityAuthorizer implements SecurityAuthorizer {
    @inject @CompositeSecurityAuthorizerAnnot
    List<SecurityAuthorizer> authorizers; //Field Injection
}

I want to inject the authorizers field a List<SecurityAuthorizer> value.

In my module , I have the following:

@Override
protected void configure() {
  bind(CompositeSecurityAuthorizer.class).in(Singleton.class);
  bind(StoreAuthorizer.class).in(Singleton.class);
  bind(SecurityAuthorizer.class)
      .annotatedWith(CompositeSecurityAuthorizerAnnot.class)
      .to(CompositeSecurityAuthorizer.class);
}

@Provides @CompositeSecurityAuthorizerAnnot
List<SecurityAuthorizer> provideAuthorizersList()
{
    List<SecurityAuthorizer> authList = new ArrayList<SecurityAuthorizer>();
    //How do I add StoreAuthorizer while maintaining a Singleton?
    //Will the line below do it through Guice magic?
    //authList.add(new StoreAuthorizer());
    return authList;
}

My question is embedded in the code comments. When I'm adding StoreAuthorizer to that List<SecurityAuthorizer>:

Upvotes: 5

Views: 3802

Answers (1)

ColinD
ColinD

Reputation: 110104

Provider methods allow injected arguments. The StoreAuthorizer passed to the method here will be the singleton bound in your module. Guice doesn't and can't do anything magical if you call a constructor yourself.

@Provides @CompositeSecurityAuthorizerAnnot
List<SecurityAuthorizer> provideAuthorizersList(StoreAuthorizer storeAuthorizer)
{
    List<SecurityAuthorizer> authList = new ArrayList<SecurityAuthorizer>();
    authList.add(storeAuthorizer);
    return authList;
}

As an aside, you may want to consider using the Guice Multibindings extension to create a Set<SecurityAuthorizer> rather than doing this yourself.

Upvotes: 8

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