save id generator locally

atms-api/src/main/java/pwc/taxtech/atms/common/util/SnowFlake.java

+package pwc.taxtech.atms.common.util;
+
+public class SnowFlake {
+    /**
+     * 起始的时间戳
+     */
+    private final static long START_STAMP = 1529337600000L;
+
+    /**
+     * 每一部分占用的位数
+     */
+    private final static long SEQUENCE_BIT = 12; //序列号占用的位数
+    private final static long MACHINE_BIT = 5;   //机器标识占用的位数
+    private final static long DATA_CENTER_BIT = 5;//数据中心占用的位数
+
+    /**
+     * 每一部分的最大值
+     */
+    private final static long MAX_DATA_CENTER_NUM = -1L ^ (-1L << DATA_CENTER_BIT);
+    private final static long MAX_MACHINE_NUM = -1L ^ (-1L << MACHINE_BIT);
+    private final static long MAX_SEQUENCE = -1L ^ (-1L << SEQUENCE_BIT);
+
+    /**
+     * 每一部分向左的位移
+     */
+    private final static long MACHINE_LEFT = SEQUENCE_BIT;
+    private final static long DATA_CENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
+    private final static long TIMESTAMP_LEFT = DATA_CENTER_LEFT + DATA_CENTER_BIT;
+
+    private long dataCenterId;  //数据中心
+    private long machineId;     //机器标识
+    private long sequence = 0L; //序列号
+    private long lastStamp = -1L;//上一次时间戳
+
+    public SnowFlake(long dataCenterId, long machineId) {
+        if (dataCenterId > MAX_DATA_CENTER_NUM || dataCenterId < 0) {
+            throw new IllegalArgumentException("dataCenterId can't be greater than MAX_DATA_CENTER_NUM or less than 0");
+        }
+        if (machineId > MAX_MACHINE_NUM || machineId < 0) {
+            throw new IllegalArgumentException("machineId can't be greater than MAX_MACHINE_NUM or less than 0");
+        }
+        this.dataCenterId = dataCenterId;
+        this.machineId = machineId;
+    }
+
+    /**
+     * 产生下一个ID
+     *
+     * @return id
+     */
+    public synchronized long nextId() {
+        long currStamp = getNewStamp();
+        if (currStamp < lastStamp) {
+            throw new RuntimeException("Clock moved backwards.  Refusing to generate id");
+        }
+
+        if (currStamp == lastStamp) {
+            //相同毫秒内，序列号自增
+            sequence = (sequence + 1) & MAX_SEQUENCE;
+            //同一毫秒的序列数已经达到最大
+            if (sequence == 0L) {
+                currStamp = getNextMill();
+            }
+        } else {
+            //不同毫秒内，序列号置为0
+            sequence = 0L;
+        }
+
+        lastStamp = currStamp;
+
+        return (currStamp - START_STAMP) << TIMESTAMP_LEFT //时间戳部分
+                | dataCenterId << DATA_CENTER_LEFT       //数据中心部分
+                | machineId << MACHINE_LEFT             //机器标识部分
+                | sequence;                             //序列号部分
+    }
+
+    private long getNextMill() {
+        long mill = getNewStamp();
+        while (mill <= lastStamp) {
+            mill = getNewStamp();
+        }
+        return mill;
+    }
+
+    private long getNewStamp() {
+        return System.currentTimeMillis();
+    }
+
+    public static void main(String[] args) {
+        SnowFlake snowFlake = new SnowFlake(1, 1);
+
+        for (int i = 0; i < (1 << 12); i++) {
+            System.out.println(snowFlake.nextId());
+        }
+
+    }
+}

atms-api/src/main/java/pwc/taxtech/atms/service/impl/DistributedIDService.java

+package pwc.taxtech.atms.service.impl;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Service;
+import pwc.taxtech.atms.common.util.SnowFlake;
+
+import javax.annotation.PostConstruct;
+
+@Service
+public class DistributedIDService extends BaseService {
+    @Value("${distributed_id_datacenter}")
+    private Integer dataCenterId;
+    @Value("${distributed_id_machine}")
+    private Integer machineId;
+
+    private SnowFlake snowFlake;
+
+    @PostConstruct
+    public void init() {
+        snowFlake = new SnowFlake(dataCenterId, machineId);
+    }
+
+    /**
+     * 获取ID
+     *
+     * @return long
+     */
+    public long nextId() {
+        return snowFlake.nextId();
+    }
+}