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Resolve generic type in subclass? [message #1775272]

Fri, 27 October 2017 06:30

The Hay

Messages: 2
Registered: October 2017

Junior Member

Here is a scenario:

public class Super<T> {
protected T id;
}

public class Sub extends Super<Long> {}

Is there a way to evaluate the type of the field "id" within the scope of the class "Sub" using available API? I'm currently using JDT dom API, but other public API is acceptable.

dịch vụ tìm người giúp việc nhà tphcm, Với phương châm "Trao niềm tin - Nhận hạnh phúc", Dịch vụ Sao Mai

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Re: Resolve generic type in subclass? [message #1775451 is a reply to message #1775272]

Mon, 30 October 2017 10:15

Eclipse User

At runtime, it returns Object because of type-erasure which replaces all generic types with Object. There is no way to determine at runtime what generic type was provided at compile-time.

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Re: Resolve generic type in subclass? [message #1775453 is a reply to message #1775451]

Mon, 30 October 2017 10:43

Ed Willink

Messages: 7655
Registered: July 2009

Senior Member

Hi

The resolved T is indeed just Object. However if you are prepared to use knowledge of your code you know that T is the first type argument so getClass().getTypeParameters()[0] should get you well on the way,

If you use ASM, there may be helpers that can resolve the original T.

Regards

Ed Willink

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