predicate property

I need to filter the extensions of files inside a pathfield.
the right way is the predicate.

import org.apache.jackrabbit.commons.predicate.Predicate;
import org.apache.felix.scr.annotations.Component;
import org.apache.felix.scr.annotations.Property;
import org.apache.felix.scr.annotations.Service;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@Component
@Service
@Property(name = "PredicateVideo", value = "PredicateVideo")
public class PredicateVideo implements Predicate {
protected final Logger log = LoggerFactory.getLogger(this.getClass());

public boolean evaluate(Object obj) {
    log.info("test "+obj.toString());
    return true;
}

}

I have a pathfield with the property predicate equal to PredicateVideo and when i run the page i can see inside the log:

Unable to retrieve the predicate PredicateVideo

Why?

Thanks