How do I find type parameter values passed to a super class using reflection?
For example, given Bar.class, how do I find that it passes Integer.class to Foo's type parameter T?
public class Foo<T> {
}
public class Bar extends Foo<Integer> {
}
Thanks!
You can try
ParameterizedType type = (ParameterizedType) Bar.class.getGenericSuperclass();
System.out.println(type.getRawType()); // prints; class Foo
Type[] actualTypeArguments = type.getActualTypeArguments();
System.out.println(actualTypeArguments[0]); // prints; class java.lang.Integer
This only works because Bar is a class which extends a specific Foo. If you declared a variable like the following, you wouldn't be able to determine the parameter type of intFoo at runtime.
Foo<Integer> intFoo = new Foo<Integer>();
public class Bar extends Foo<Integer> {
public Class getTypeClass {
ParameterizedType parameterizedType =
(ParameterizedType) getClass().getGenericSuperClass();
return (Class) parameterizedtype.getActualTypeArguments()[0];
}
}
The given above should work in most of the practical situations,but not guaranteed, because of type erasure, there is no way to do this directly.
