雪花算法生成id
# 雪花算法工具类生成 id
package com.wx.wiki.util;
import org.springframework.stereotype.Component;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
/**
* Twitter 的分布式雪花ID算法
*/
@Component
public class SnowFlake {
/**
* 起始的时间戳
*/
private final static long START_STAMP = 1609459200000L; // 2021-01-01 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 = 5; //机器标识占用的位数
private final static long DATACENTER_BIT = 5;//数据中心占用的位数
/**
* 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 = 1; //数据中心
private long machineId = 1; //机器标识
private long sequence = 0L; //序列号
private long lastStmp = -1L;//上一次时间戳
public SnowFlake() {
}
public SnowFlake(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
*/
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) {
currStmp = getNextMill();
}
} else {
//不同毫秒内,序列号置为0
sequence = 0L;
}
lastStmp = currStmp;
return (currStmp - START_STAMP) << 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 void main(String[] args) throws ParseException {
// 时间戳
// System.out.println(System.currentTimeMillis());
// System.out.println(new Date().getTime());
//
// String dateTime = "1970-01-01 08:00:00";
// SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
// System.out.println(sdf.parse(dateTime).getTime());
SnowFlake snowFlake = new SnowFlake(1, 1);
long start = System.currentTimeMillis();
for (int i = 0; i < 10; i++) {
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
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
110
111
112
113
114
115
116
117
118
119
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
110
111
112
113
114
115
116
117
118
119
精度丢失
雪花算法得到的 ID 较长,传到前端后,精度丢失
库中存的值:23754851322302474
后端取的值:23754851322302474
前端得到值:23754851322302470,数据被四舍五入了
# 解决办法
将Long
类型转为String
,再传给前端
# 方法 1:单个注解
@JsonSerialize(using= ToStringSerializer.class)
private Long id;
1
2
2
# 方法 2:统一配置
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.module.SimpleModule;
import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
/**
* 统一注解,解决前后端交互Long类型精度丢失的问题
*/
@Configuration
public class JacksonConfig {
@Bean
public ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder) {
ObjectMapper objectMapper = builder.createXmlMapper(false).build();
SimpleModule simpleModule = new SimpleModule();
simpleModule.addSerializer(Long.class, ToStringSerializer.instance);
objectMapper.registerModule(simpleModule);
return objectMapper;
}
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
编辑 (opens new window)
上次更新: 2021/12/20, 23:58:05