在系统中,除了使用数据库表本身的Id,如何生成各种业务Id?一下记录几种生成Id的方式:
1) 首先创建一个数据库表,来记录当前的业务Id
CREATE TABLE `global_auto_number` ( `id` varchar(32) NOT NULL, `version_optimized_lock` int(11) NOT NULL, `business_key` varchar(255) NOT NULL COMMENT 'Can use full business class name as business key', `current_num` bigint(22) NOT NULL COMMENT 'current number', PRIMARY KEY (`id`), UNIQUE KEY `UK_AUTO_NUMBER` (`business_key`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8
2) 获取Id的方法:
int currentCount = jdbcTemplate.update("update global_auto_number set current_num = LAST_INSERT_ID(current_num + 1) where business_key = ?", new Object[] {businessKey}); if(currentCount == 0) { jdbcTemplate.update("insert into global_auto_number (id, version_optimized_lock, business_key, current_num) values (?, 1, ?, 0)", new Object[] {UUIDGenerator.generateUUID(),businessKey}); jdbcTemplate.update("update global_auto_number set current_num = LAST_INSERT_ID(current_num + 1) where business_key = ?", new Object[] {businessKey}); } return jdbcTemplate.queryForLong("select LAST_INSERT_ID()");
3) 按照业务逻辑格式化获取的Id。例如:
String.format("SEQ%09d", 123)
4) 注意事务需要用REQUIRES_NEW,否则在并发环境下会出现大量乐观锁问题。
2. 使用随机数来生成随机的Id,例如使用同一个Id来追踪后台响应用户操作的各种log
public static String generateRandomId() { byte[] bytes = new byte[10]; try { SecureRandom.getInstance("SHA1PRNG").nextBytes(bytes); } catch (NoSuchAlgorithmException e) { throw new RuntimeException(e); } return toHexString(bytes); } final protected static char[] hexArray = "0123456789ABCDEF".toCharArray(); public static String toHexString(byte[] bytes) { char[] hexChars = new char[bytes.length * 2]; for ( int j = 0; j < bytes.length; j++ ) { int v = bytes[j] & 0xFF; hexChars[j * 2] = hexArray[v >>> 4]; hexChars[j * 2 + 1] = hexArray[v & 0x0F]; } return new String(hexChars); }