Hi Miguel,
the issue that you are observing is due to Java's type erasure.
"new MyClass<String>()" is always erasured to "new MyClass()" by the
Java compiler so it is impossible for Flink to extract something.
For classes in declarations like
class MyClass<String> extends ... {
...
}
the compiler adds the actual generic and Flink can extract it. So for
classes the generics remain but generics passed to objects are erasured.
Regards,
Timo
Am 16.08.18 um 22:28 schrieb Miguel Coimbra:
Hello,
I have some code which compiles correctly (Flink 1.4) under Java 8.
It uses generic types.
While it compiles correctly, the execution fails with the error:
org.apache.flink.api.common.functions.InvalidTypesException: Type of
TypeVariable 'K' in 'class X' could not be determined.
This is my main:
public static void main(final String[] args) {
X<Long> x = new X();
}
This is my class X:
public class X<K>{
public X() { TypeInformation<K> keySelector = TypeInformation.of(new
TypeHint<K>(){}); } }
Perhaps I'm lacking knowledge on the way Java's generics work, but why
can't Flink determine the TypeVariable of 'K'?
As I am instantiating X parameterized as a Long, that information
should eventually reach Flink and the constructor of X would be
equivalent to this:
public X() { TypeInformation<Long> keySelector =
TypeInformation.of(new TypeHint<Long>(){}); }
During execution, however, this error pops up.
What am I missing here, and what is the best way to achieve this
generic behavior in a Flink-idiomatic way?
Thank you very much for your time.
