acl/src/main/java/org/springframework/security/acls/AclPermissionEvaluator.java
public boolean hasPermission(Authentication authentication, Object domainObject,
			Object permission) {
		if (domainObject == null) {
			return false;
		}

		ObjectIdentity objectIdentity = objectIdentityRetrievalStrategy
				.getObjectIdentity(domainObject);

		return checkPermission(authentication, objectIdentity, permission);
	}
public boolean hasPermission(Authentication authentication, Object domainObject,
			Object permission) {
		if (domainObject == null) {
			return false;
		}

		ObjectIdentity objectIdentity = objectIdentityRetrievalStrategy
				.getObjectIdentity(domainObject);

		return checkPermission(authentication, objectIdentity, permission);
	}
Determines whether the user has the given permission(s) on the domain object using
the ACL configuration. If the domain object is null, returns false (this can always
be overridden using a null check in the expression itself).