Hi Joe,
thanks for the explanation. We switched to rather iterating over
….getParameters() and take it from there. Do you think it makes sense to leave
a note about this in the Javadoc?
Cheers,
Ollie
> Am 26.02.2021 um 22:38 schrieb Joe Darcy <joe.da...@oracle.com>:
>
> Hello Oliver,
>
> This is long-standing if surprising and under-documented behavior.
>
> The getGenericFoo methods, when generic type information is present, give a
> source-level view of the element. At a source level, the implicit outer this
> parameter is not present and thus omitted by
> constructor.getGenericParameterTypes for the constructor in question.
>
> HTH,
>
> -Joe
>
> On 2/26/2021 5:41 AM, Oliver Drotbohm wrote:
>> Previously sent to the wrong list. Sorry for the double post.
>>
>> Von: Oliver Drotbohm <odrotb...@vmware.com>
>> Betreff: Inconsistency in Constructor.getGenericParameterTypes()
>> Datum: 25. Februar 2021 um 10:03:12 MEZ
>> An: jdk-...@openjdk.java.net
>>
>> Hi all,
>>
>> we've just ran into the following issue: for a non-static, generic inner
>> class with a constructor declaring a generic parameter, a call to
>> constructor.getGenericParameterTypes() does not return the enclosing class
>> parameter type. Is that by intention? If so, what's the reasoning behind
>> that?
>>
>> Here's a the output of a reproducer (below):
>>
>> static class StaticGeneric<T> - names: value, string
>> static class StaticGeneric<T> - parameters: [class java.lang.Object, class
>> java.lang.String]
>> static class StaticGeneric<T> - generic parameters: [T, class
>> java.lang.String]
>>
>> class NonStaticGeneric<T> - names: this$0, value, String
>> class NonStaticGeneric<T> - parameters: [class Sample, class
>> java.lang.Object, class java.lang.String]
>> class NonStaticGeneric<T> - generic parameters: [T, class java.lang.String]
>>
>> class NonStaticNonGeneric - names: this$0, String
>> class NonStaticNonGeneric - parameters: [class Sample, class
>> java.lang.String]
>> class NonStaticNonGeneric - generic parameters: [class Sample, class
>> java.lang.String]
>>
>> Note how the constructor of the NonStaticGeneric<T> type exposes three
>> parameter names, three parameter types but omits the enclosing class
>> parameter in the list of generic parameter types.
>>
>> Tested on JDK 8 to 15. Same behavior.
>>
>> Cheers,
>> Ollie
>>
>>
>> class Sample {
>>
>> public static void main(String[] args) {
>>
>> Constructor<?> first =
>> StaticGeneric.class.getDeclaredConstructors()[0];
>>
>> System.out.println("static class StaticGeneric<T> - names: "
>> +
>> Arrays.stream(first.getParameters()).map(Parameter::getName).collect(Collectors.joining(",
>> ")));
>> System.out.println("static class StaticGeneric<T> - parameters:
>> " + Arrays.toString(first.getParameterTypes()));
>> System.out.println(
>> "static class StaticGeneric<T> - generic
>> parameters: " + Arrays.toString(first.getGenericParameterTypes()));
>>
>> System.out.println();
>>
>> Constructor<?> second =
>> NonStaticGeneric.class.getDeclaredConstructors()[0];
>> System.out.println("class NonStaticGeneric<T> - names: "
>> +
>> Arrays.stream(second.getParameters()).map(Parameter::getName).collect(Collectors.joining(",
>> ")));
>> System.out.println("class NonStaticGeneric<T> - parameters: " +
>> Arrays.toString(second.getParameterTypes()));
>> System.out
>> .println(
>> "class NonStaticGeneric<T> -
>> generic parameters: " + Arrays.toString(second.getGenericParameterTypes()));
>>
>> System.out.println();
>>
>> Constructor<?> third =
>> NonStaticNonGeneric.class.getDeclaredConstructors()[0];
>> System.out.println("class NonStaticNonGeneric - names: "
>> +
>> Arrays.stream(third.getParameters()).map(Parameter::getName).collect(Collectors.joining(",
>> ")));
>> System.out.println("class NonStaticNonGeneric - parameters: " +
>> Arrays.toString(third.getParameterTypes()));
>> System.out
>> .println(
>> "class NonStaticNonGeneric -
>> generic parameters: " + Arrays.toString(third.getGenericParameterTypes()));
>> }
>>
>> static class StaticGeneric<T> {
>> StaticGeneric(T value, String string) {}
>> }
>>
>> class NonStaticGeneric<T> {
>> NonStaticGeneric(T value, String String) {}
>> }
>>
>> class NonStaticNonGeneric {
>> NonStaticNonGeneric(String String) {}
>> }
>> }
>>
