接口：
/**
* id生成器
*/
public interface IdGenerator {
String next();
}实现类：
/**
* 分布式ID自增算法<br/>
* 来自网络Twitter Snowflake 算法
*
*/
public class DistributedIdGenerator implements IdGenerator{
private final long workerId;
private final static long twepoch = 1361753741828L;
private long sequence = 0L;
private final static long workerIdBits = 4L;
public final static long maxWorkerId = -1L ^ -1L << workerIdBits;
private final static long sequenceBits = 10L;
private final static long workerIdShift = sequenceBits;
private final static long timestampLeftShift = sequenceBits + workerIdBits;
public final static long sequenceMask = -1L ^ -1L << sequenceBits;
private long lastTimestamp = -1L;
public DistributedIdGenerator(final long workerId) {
super();
if (workerId > maxWorkerId || workerId < 0) {
throw new IllegalArgumentException(String.format(
"worker Id can't be greater than %d or less than 0",
maxWorkerId));
}
this.workerId = workerId;
}
public synchronized String next() {
long timestamp = this.timeGen();
if (this.lastTimestamp == timestamp) {
this.sequence = (this.sequence + 1) & sequenceMask;
if (this.sequence == 0) {
System.out.println("###########" + sequenceMask);
timestamp = this.tilNextMillis(this.lastTimestamp);
}
} else {
this.sequence = 0;
}
if (timestamp < this.lastTimestamp) {
try {
throw new Exception(
String.format(
"Clock moved backwards. Refusing to generate id for %d milliseconds",
this.lastTimestamp - timestamp));
} catch (Exception e) {
e.printStackTrace();
}
}
this.lastTimestamp = timestamp;
long nextId = ((timestamp - twepoch << timestampLeftShift))
| (this.workerId << workerIdShift) | (this.sequence);
return "" + nextId;
}
private long tilNextMillis(final long lastTimestamp) {
long timestamp = this.timeGen();
while (timestamp <= lastTimestamp) {
timestamp = this.timeGen();
}
return timestamp;
}
private long timeGen() {
return System.currentTimeMillis();
}
}
应用实例：
@Service
public class StudentsApplication(){
@Autowired
private IdGenerator idGenerator;
public void add(){
Student s = new Student();
s.setId(idGenerator.next());
}
}
来自网络Twitter Snowflake 算法