According to JSR 308 (Java Type Annotations) it is possible to annotate any type using ElementType.TYPE_USE:
import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.RetentionPolicy.*;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
@Target({ TYPE_USE })
@Retention(RUNTIME)
public @interface MyAnnotation {
String value();
}
How to get the annotated value from a function at runtime?
import java.util.function.Consumer;
import org.junit.Assert;
import org.junit.Test;
public class TestFunctionAnnotation {
@Test
public void test() {
Consumer<TestFunctionAnnotation> fun = @MyAnnotation("NoJoke") TestFunctionAnnotation::test;
Assert.assertEquals("NoJoke", fun.getClass().getAnnotatedSuperclass().getAnnotation(MyAnnotation.class));
// expected:<NoJoke> but was:<null>
}
}
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