public void assertAuthorized(Annotation a) throws UnauthorizedException {
        throw new UnauthenticatedException("Attempting to perform a denied operation.");
    }
Causes a {@link UnauthorizedException} to be thrown if a DenyAll annotation is present.

@param a the annotation to check for one or more roles
@throws UnauthorizedException when the DenyAll annotation is present
core/src/main/java/org/apache/shiro/authz/aop/DenyAllAnnotationHandler.java