Question

I have a situation where I need to programmatically set something that has a parameter of Class<? extends Annotation> but I cannot figure out how to pass in an Annotation class to this method.

For example, if I have javax.persistence.Entity and I try setAnnotation(javax.persistence.Entity.class) I get an error saying Class<Entity> is not applicable for those arguments. However, that is a class that has the @interface attribute; it’s obviously an annotation. What am I doing wrong and how can I appropriately send in a value?

The reason for this is I’m going from Spring XML configuration to class @Configuration. It’s easy enough to do this in an xml file with:

<property name="annotation" value="javax.persistence.Entity" />

but I don’t know what Spring is doing to make that work.

public class Stuff {
    private List<Class<? extends Annotation>> annotations;

    public List<Class<? extends Annotation>> getAnnotations() {
        return annotations;
    }

    public void setAnnotations(List<Class<? extends Annotation>> annotations) {
        this.annotations = annotations;
    }
}

public class StuffTest {


    @Test
    public void test() {

        new Stuff().setAnnotations(Collections.singletonList(javax.persistence.Entity.class));
        // this does not compile
    }
}

Edit:

List list = new ArrayList();
list.add(javax.persistence.Entity.class);
stuff.setAnnotations(list);

works but is there a better way?

Answer 1

This is the API that works for me (both using the Eclipse and javac compilers):

public void setAnnotations(
  Collection<? extends Class<? extends Annotation>> annotations) {

Of course, this would mean you’d have to change some of the inner workings of Stuff itself…

Note also the Collection argument type, as Collections.singleton() returns a Set, not a List. Maybe you meant to use a Collections.singletonList() instead?