Re: Can this callback mechanism be generified?

Couple of notes, nothing terribly important...

Casper Bang wrote:
> Mark Space wrote:
>> I agree this part is easier to read, I just don't see the rest of the 
>> code much improved (pulling the type by name from the interface name 
>> was a pretty good trick.  With luck, we'll get reifiable types in Java 
>> 7 and then nonsense like that will be unneeded.)
> 
> I did some reading (Java Generics and Collections) and it turns out 
> there are ways to get to the types, in spite of erasure. So now I do it 
> a bit cleaner, no pulling apart a string and no reflection required:
> 
You expect this to return Class<T>, don't you? So why don't you declare 
it that way.
> private <T> Class extractGenericType(Callback<T> callback)
> {
>     Type[] interfaces = callback.getClass().getGenericInterfaces();
> 
>     if(interfaces.length != 1 || !(interfaces[0] instanceof 
> ParameterizedType))
Don't assume it should be exactly one, it would probably be better to go 
through a loop.
>         throw new RuntimeException("You must supply a generified 
> Callback with a single parameterized type");
It would be more appropriate to throw an IllegalArgumentException I 
think.  It would probably be even more appropriate to throw a 
CallbackException of your own creation.
>     Type[] parmTypes = 
> ((ParameterizedType)interfaces[0]).getActualTypeArguments();
> 
>     return (Class)parmTypes[0];
> }
>

Hope this is useful.


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Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>