[FELIX-5996] Remove generic parameter in DM Component interface

• Type: Task
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: org.apache.felix.dependencymanager-r13
• Fix Version/s: org.apache.felix.dependencymanager-r15
• Component/s: Dependency Manager
• Assignee: Pierre De Rop
• Reporter: Pierre De Rop
• Created: 06/Dec/18 09:58
• Updated: 24/Dec/18 09:40
• Resolved: 19/Dec/18 14:53

Description

Since dm-r13, the Component interface is now taking a generic parameter so it make it easier to define extended components like adapters.

So, with this new model, it looks like the following:

public interface Component<T extends Component<T>> {
   T setInterface(String service, Dictionary properties)
   T setImplementation(Object ob);
   ...
}
public interface AdapterComponent extends Component<AdapterComponent> {
   AdapterComponent setAdaptee(Class<?> service, String filter);
   AdapterComponent setAdapteeCallbacks(String add, String change, String remove, String swap);
   ...
}

and you can now do something like this:

Component adapter = createAdapterComponent()
  .setAdaptee(Adaptee.class, "(foo=bar)")
  .setAdapteeCallbacks("setAdaptee", "changeAdaptee", null, null)
  .setImplementation(AdapterImpl.class)
  .setInterface(AdapterService.class, null)
  .add(createServiceDependency().setService(LogService.class));

now, while using the generic parameter simplify the declaration of component adapters, it has a drawback: the Component now takes a generic parameter, and old code using simple components now generates a compilation warning:

Component adapter = createComponent()
 .setImplementation(SimpleComponent.class)
 ...

so, the above example generates a compilation warning, and you now have to declare "?" in order to get rid of the warning:

Component<?> adapter = createComponent()
 .setImplementation(SimpleComponent.class)
 ...

that being said, maybe we can refactor in order to get rid of the generic parameter, by copying the top level component methods in sub interfaces, like this:

public interface Component {
 Component setInterface(String service, Dictionary properties);
 Component setImplementation(Object ob);
 ...
 }

public interface AdapterComponent extends Component
{
 // Component methods with specialized signatures 
AdapterComponent setInterface(String service, Dictionary properties) 
AdapterComponent setImplementation(Object ob);

// AdapterComponent methods
AdapterComponent methods AdapterComponent setAdaptee(Class<?> service, String filter); 
AdapterComponent setAdapteeCallbacks(String add, String change, String remove, String swap); 
 }