Why are annotations under Android such a performance issue (slow)?

Question

I\'m the lead author of ORMLite which uses Java annotations on classes to build database schemas. A big startup performance problem for our package turns out to be the call

Answer 1

Here's a generic version of Gray's & user931366's idea:

public class AnnotationElementsReader {

    private static Field elementsField;
    private static Field nameField;
    private static Method validateValueMethod;

    public static HashMap getElements(Annotation annotation)
            throws Exception {
        HashMap map = new HashMap();
        InvocationHandler handler = Proxy.getInvocationHandler(annotation);
        if (elementsField == null) {
            elementsField = handler.getClass().getDeclaredField("elements");
            elementsField.setAccessible(true);
        }
        Object[] annotationMembers = (Object[]) elementsField.get(handler);
        for (Object annotationMember : annotationMembers) {
            if (nameField == null) {
                Class cl = annotationMember.getClass();
                nameField = cl.getDeclaredField("name");
                nameField.setAccessible(true);
                validateValueMethod = cl.getDeclaredMethod("validateValue");
                validateValueMethod.setAccessible(true);
            }
            String name = (String) nameField.get(annotationMember);
            Object val = validateValueMethod.invoke(annotationMember);
            map.put(name, val);
        }
        return map;
    }

}

I've benchmarked an annotation with 4 elements.
Millisecond times for 10000 iterations of either getting values of all of them or calling the method above:

     Device        Default  Hack
HTC Desire 2.3.7    11094   730
Emulator 4.0.4      3157    528
Galaxy Nexus 4.3    1248    392

Here's how I've integrated it into DroidParts: https://github.com/yanchenko/droidparts/commit/93fd1a1d6c76c2f4abf185f92c5c59e285f8bc69.