Add ConverterProvider type to handle Converter retrieval for parameterized type

Description

Suppose that I create a parameterized type as follow:

public class MyObject<T> {

	...

}

If I want to use this parameterized type in the following injection points

@Inject
@ConfigProperty(name = "property1")
private MyObject<Type1> property1;

@Inject
@ConfigProperty(name = "property2")
private MyObject<Type2> property2;

I have two provide a global converter or an implicit converter. But the problem with both of them is they won’t tell nothing me about the type argument of the parameterized type at the given injection point.

Proposal

So my proposal would be to add a ConverterProvider type as follow to handle this case

public interface ConverterProvider {

    public <T> Converter<T> getConverter(Class<T> rawType, Type genericType);

}

Just like Converter this ConverterProvider would be discovered by SPI or provided programatically. Then it would be invoked when resolving injection points to retrieve the right Converter. If no ConverterProvider is available or if it does not provide no eligible Converter then the current Converter retrieval mechanism is applied.

The concept of ConverterProvider is taken form JAX-RS spec where the equivalent is ParamConverterProvider.

WDYT ? Am I missing something ?

Thanks

[radcortez]

We probably need to stay away from adding a direct dependency to CDI, so my preference would be to add a custom the like JAX-RS.

[jbee]

In summary, as @NicoNes points out the downside of Type in the signature is loss of type safety when used programmatically. While javax.enterprise.util.TypeLiteral does enforce type safety it does not allow to use the Type instance extracted via reflection as it is the case for injection points. In-between these two is using some wrapper type with a generic (like GenericType) which does allow wrapping a Type instance (unsafe) but also can be used type safe but cannot enforce it.