acl/src/main/java/org/springframework/security/acls/jdbc/JdbcMutableAclService.java
protected Long retrieveObjectIdentityPrimaryKey(ObjectIdentity oid) {
		try {
			return jdbcOperations.queryForObject(selectObjectIdentityPrimaryKey, Long.class,
					oid.getType(), oid.getIdentifier().toString());
		}
		catch (DataAccessException notFound) {
			return null;
		}
	}
protected Long retrieveObjectIdentityPrimaryKey(ObjectIdentity oid) {
		try {
			return jdbcOperations.queryForObject(selectObjectIdentityPrimaryKey, Long.class,
					oid.getType(), oid.getIdentifier().toString());
		}
		catch (DataAccessException notFound) {
			return null;
		}
	}
Retrieves the primary key from the acl_object_identity table for the passed
ObjectIdentity. Unlike some other methods in this implementation, this method will
NOT create a row (use {@link #createObjectIdentity(ObjectIdentity, Sid)} instead).

@param oid to find

@return the object identity or null if not found