Mybatis-plus 自定义ID生成器

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
/**
 * 雪花算法生成唯一的有序的序列号
 */
public class SnowflakeUtils {
   /**
    * 起始的时间戳
    */
   private final static long START_STMP = 1567267200000L;//2019-09-01 00:00:00

   /**
    * 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 = 8;   //机器标识占用的位数，256个机器
   private final static long DATACENTER_BIT = 2;//数据中心占用的位数，4个数据中心

   /**
    * 每一部分的最大值
    */
   private final static long MAX_DATACENTER_NUM = -1L ^ (-1L << DATACENTER_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 DATACENTER_LEFT = SEQUENCE_BIT + MACHINE_BIT;
   private final static long TIMESTMP_LEFT = DATACENTER_LEFT + DATACENTER_BIT;

   private long datacenterId;  //数据中心
   private long machineId;     //机器标识
   private long sequence = 0L; //序列号
   private long lastStmp = -1L;//上一次时间戳

   public SnowflakeUtils(long datacenterId, long machineId) {
       if (datacenterId > MAX_DATACENTER_NUM || datacenterId < 0) {
           throw new IllegalArgumentException("datacenterId can't be greater than "+MAX_DATACENTER_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
    */
   public synchronized long nextId() {
       long currStmp = getNewstmp();
       if (currStmp < lastStmp) {
           throw new RuntimeException("Clock moved backwards.  Refusing to generate id");
       }

       if (currStmp == lastStmp) {
           //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) {
               //循环获取多几次，尽可能地避免不可能的可能
               for(int i = 0; i< 100; i ++){
                   currStmp = getNextMill();
                   if (currStmp != lastStmp){
                       break;
                   }
               }
           }
       } else {
           //不同毫秒内，序列号置为0
           sequence = 0L;
       }

       lastStmp = currStmp;

       return (currStmp - START_STMP) << TIMESTMP_LEFT //时间戳部分
               | datacenterId << DATACENTER_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 = getNewstmp();
       while (mill <= lastStmp) {
           mill = getNewstmp();
       }
       return mill;
   }

   private long getNewstmp() {
       return System.currentTimeMillis();
   }

   public static long getId() {
       SnowflakeUtils idGenerator = new SnowflakeUtils(1, 1);
       return idGenerator.nextId();
   }

//    public static void main(String[] args) {
//        SnowflakeUtils snowFlake = new SnowflakeUtils(1, 1);
//
//        long start = System.currentTimeMillis();
//        System.out.println(snowFlake.nextId());
//        System.out.println(System.currentTimeMillis() - start);
//    }
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
/**
 * mybaits 自定义主键生成器
 */
@Component // 加入到spring容器中
public abstract class MybatisKeyGenerator implements IdentifierGenerator {
   @Value("${server.worker-id:1}")
   private Integer workerId;

   @Value("${server.data-center-id:1}")
   private Integer dataCenterId;

   @Override
   public Number nextId(Object entity) {
   		//上面的雪花算法
       long uid = new SnowflakeUtils(workerId, dataCenterId).nextId();
       return uid;
   }
}

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
//使用自定义ID生成器
@Data
@TableName("am_contract")
@EqualsAndHashCode(callSuper = true)
@ApiModel(value = "合同信息")
public class AmContract extends BaseEntity<AmContract> {
    private static final long serialVersionUID = 1L;

    /**
     * 主键
     */
    @TableId(type = IdType.ASSIGN_ID) // 使用IdType.ASSIGN_ID
    @ApiModelProperty(value = "主键")
    private Long id;
    /**
     * 合同号
     */
    @ApiModelProperty(value = "合同号")
    private String no;
    /**
     * 修改者Name
     */
    @TableField(exist = false)
    @ApiModelProperty(value = "修改者Name")
    private String updateByName;
}