CODEWITHSUNDEEP
javadependency-injectionguice
ab11
ab11

Reputation: 20090

With Guice, how to provide different instances of the same Type?

I have types A and B. I would like to bind two instances of Type A, and provide two instances of Type B - with instances of Type B being created based on an instance of Type A.

I attempt to do this below, but the call to providesB2() results in this exception:

A binding to javax.sql.DataSource was already configured at ...providesB1()

I imagine an easy solution to this is not to provide two instances of Type B, rather to have my provider methods return Types C and D, both of which extend B. But is there a way to accomplish this while providing two instances of Type B?

@BindingAnnotation
@Retention(RetentionPolicy.RUNTIME)
@interface A1 {}

@BindingAnnotation
@Retention(RetentionPolicy.RUNTIME)
@interface A2 {}

//....

(A.class).annotatedWith(A1.class).toInstance(aInstance1);
(A.class).annotatedWith(A2.class).toInstance(aInstance2);

@Provides
@Singleton
@Inject
B providesB1(@A1 a) {
  return new B(a)
}

@Provides
@Singleton
@Inject
B providesB2(@A2 a) {
  return new B(a)
}

Upvotes: 0

Views: 399

Answers (1)

Louis Wasserman
Louis Wasserman

Reputation: 198014

You already distinguished the two different A's with binding annotations @A1 and @A2. You just need to distinguish the two different B's with binding annotations as well, by adding whatever your annotation is to the list of annotations for providesB1 and providesB2.

Upvotes: 2

Related Questions