ProviderSkeleton.java 文件源码

/**
 * Utility method for calling an arbitrary method in an annotation.
 *
 * @param element the element that was annotated, either a class or method
 * @param annotation the class of the annotation we're interested in
 * @param methodName the name of the method in the annotation we wish
 * to call.
 * @param defaultValue the value to return if the annotation doesn't
 * exist, or we couldn't invoke the method for some reason.
 * @return the result of calling the annotation method, or the default.
 */
protected static Object getAnnotationValue(
        AnnotatedElement element, Class<? extends Annotation> annotation,
        String methodName, Object defaultValue) {
    Object ret = defaultValue;
    try {
        Method m = annotation.getMethod(methodName);
        Annotation a = element.getAnnotation(annotation);
        ret = m.invoke(a);
    } catch (NoSuchMethodException e) {
        assert false;
    } catch (IllegalAccessException e) {
        assert false;
    } catch (InvocationTargetException e) {
        assert false;
    } catch (NullPointerException e) {
        assert false;
    }
    return ret;
}