最终使用字符串如下：

String url="jdbc:oracle:thin:@(DESCRIPTION =(ADDRESS = (PROTOCOL = TCP)(HOST = scan-cluster)(PORT = 1521))(LOAD_BALANCE = yes)(FAILOVER = ON)(CONNECT_DATA =(SERVER = DEDICATED)(SERVICE_NAME = db.domain)(FAILOVER_MODE=(TYPE = SELECT)(METHOD = BASIC)(RETIRES = 20)(DELAY = 15))))";