Difference between bindAsContract and bind in HK2

Question

I am working to implement a dependency injection of a constructor in a J2EE jersey project. I am using HK2. I create a class

class MyServiceImpl implements MyService{
  @Inject
  public MyServiceImpl(String test){
   // do something
  }
}

Now, my question is when I register this dependency injection in a dependencybinder class by extending AbstractBinder, what is the difference between binding the dependency as a simple "bind" vs a "bindAsContract"?

score 6 · Accepted Answer · answered May 23 '19 at 10:04

6

When you use

bind(ServiceImpl.class).to(IService.class)

ServiceImpl is the implementation class, and IService is the contract that you advertise as the injection type. So you would use

@Inject
private IService service;

With

bindAsContract(ServiceImpl.class)

you are saying that ServiceImpl is both the implementation class and the contract to advertise as. So you would need to inject it as such.

@Inject
private ServiceImpl service;

answered May 23 '19 at 10:04

Paul Samsotha

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If I have two classes implementing the same IService interface: (1) FileServiceImpl, (2) Databaseserviceimpl, then how can we inject the appropriate classes through the interface as we need? Do we have to use any qualifier or something like that? – Debsankar Mukhopadhyay May 23 '19 at 16:00
Yes, you can use `qualifiedBy(annotationInstance)` – Paul Samsotha May 23 '19 at 16:11
How shall i take care of the constructor arguments in that case? – Debsankar Mukhopadhyay May 23 '19 at 16:42
You need to bind those as well. In the case you have in your post, since it's a String, you would need to qualify that. – Paul Samsotha May 23 '19 at 18:25

Difference between bindAsContract and bind in HK2

1 Answers1