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:
- 使用数据库表记录生成的Id,以MySQL为例:
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);
}
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