BaseModel（主键用雪花算法生成）

￡神魔★判官ぃ 2024-04-23 21:19 70阅读 0赞

*  最近项目用的BaseModel，主键生成方案用的雪花算法，感觉通用性比较强，做个存档，有需要直接复制过来用就行了：

import com.fasterxml.jackson.annotation.JsonIgnore;
    import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
    import com.fasterxml.jackson.databind.annotation.JsonSerialize;
    import com.fasterxml.jackson.databind.ser.std.ToStringSerializer;
    import com.test.utils.IdWorker;
    import org.springframework.data.annotation.CreatedDate;
    import org.springframework.data.annotation.LastModifiedDate;
    
    import javax.persistence.*;
    import java.io.Serializable;
    import java.sql.Timestamp;
    import java.util.Objects;
    
    
    @MappedSuperclass
    public class BaseModel implements Serializable {
        
    
        @Transient
        @JsonIgnore
        private final IdWorker idWorker = new IdWorker();
    
        @Id
        @Column(nullable = false, updatable = false)
        private Long id;
        @CreatedDate
        @Column(nullable = false, updatable = false)
        private Timestamp createdTime;
    
        @LastModifiedDate
        @Column(nullable = false)
        private Timestamp lastUpdatedTime;
    
        /**
         * 软删除
         */
        @Column(nullable = false,columnDefinition = "bit(1) default 0")
        private Integer isDel ;
    
        public BaseModel(){
        
            Timestamp now =new Timestamp(System.currentTimeMillis());
            this.id = id == null? idWorker.nextId() : id;
            this.createdTime = now;
            this.lastUpdatedTime =now;
            this.isDel = 0;
        }
    
        public BaseModel(Long id, Integer isDel) {
        
            this.id = id == null? idWorker.nextId() : id;
            this.createdTime = new Timestamp(System.currentTimeMillis());
            this.lastUpdatedTime = new Timestamp(System.currentTimeMillis());
            this.isDel = isDel;
        }
    
        @JsonSerialize(using = ToStringSerializer.class)
        public Long getId() {
        
            return id;
        }
    
        public void setId(Long id) {
        
            this.id = id == null? idWorker.nextId() : id;
        }
    
        public Timestamp getCreatedTime() {
        
            return createdTime;
        }
    
        public void setCreatedTime(Timestamp createdTime) {
        
            this.createdTime = createdTime;
        }
    
        public Timestamp getLastUpdatedTime() {
        
            return lastUpdatedTime;
        }
    
        public void setLastUpdatedTime(Timestamp lastUpdatedTime) {
        
            this.lastUpdatedTime = lastUpdatedTime;
        }
    
        public Integer getIsDel(){
        
            return isDel;
        }
        public Integer GetIsDel() {
        
            return isDel;
        }
    
        public void setIsDel(Integer del) {
        
            isDel = del;
        }
    
        public void eraseSystemFields(){
        
            this.setCreatedTime(null);
            this.setId(null);
            this.setIsDel(0);
            this.setLastUpdatedTime(null);
        }
    
        @Override
        public boolean equals(Object o) {
        
            if (this == o) {
        
                return true;
            }
            if (!(o instanceof BaseModel)) {
        
                return false;
            }
            BaseModel baseModel = (BaseModel) o;
            return Objects.equals(getId(), baseModel.getId()) &&
                    Objects.equals(getCreatedTime(), baseModel.getCreatedTime()) &&
                    Objects.equals(getIsDel(), baseModel.getIsDel()) &&
                    Objects.equals(getLastUpdatedTime(), baseModel.getLastUpdatedTime());
        }
    
        @Override
        public int hashCode() {
        
            return Objects.hash(getId(), getCreatedTime(), getIsDel(), getLastUpdatedTime());
        }
    }

*  IdWorker:

import java.lang.management.ManagementFactory;
 import java.net.InetAddress;
 import java.net.NetworkInterface;
 
 /**
 * 名称：IdWorker.java
 * 描述：分布式自增长ID
 * <pre>
 * Twitter的 Snowflake　JAVA实现方案
 * </pre>
 * 核心代码为其IdWorker这个类实现，其原理结构如下，我分别用一个0表示一位，用—分割开部分的作用：
 * 1||0---0000000000 0000000000 0000000000 0000000000 0 --- 00000 ---00000 ---000000000000
 * 在上面的字符串中，第一位为未使用（实际上也可作为long的符号位），接下来的41位为毫秒级时间，
 * 然后5位datacenter标识位，5位机器ID（并不算标识符，实际是为线程标识），
 * 然后12位该毫秒内的当前毫秒内的计数，加起来刚好64位，为一个Long型。
 * 这样的好处是，整体上按照时间自增排序，并且整个分布式系统内不会产生ID碰撞（由datacenter和机器ID作区分），
 * 并且效率较高，经测试，snowflake每秒能够产生26万ID左右，完全满足需要。
 * 
 * 64位ID (42(毫秒)+5(机器ID)+5(业务编码)+12(重复累加))
 *
 * @author Polim
 */
 public class IdWorker {
 
 // 时间起始标记点，作为基准，一般取系统的最近时间（一旦确定不能变动）
 private final static long twepoch = 1288834974657L;
 // 机器标识位数
 private final static long workerIdBits = 5L;
 // 数据中心标识位数
 private final static long datacenterIdBits = 5L;
 // 机器ID最大值
 private final static long maxWorkerId = -1L ^ (-1L << workerIdBits);
 // 数据中心ID最大值
 private final static long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
 // 毫秒内自增位
 private final static long sequenceBits = 12L;
 // 机器ID偏左移12位
 private final static long workerIdShift = sequenceBits;
 // 数据中心ID左移17位
 private final static long datacenterIdShift = sequenceBits + workerIdBits;
 // 时间毫秒左移22位
 private final static long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
 
 private final static long sequenceMask = -1L ^ (-1L << sequenceBits);
 /* 上次生产id时间戳 */
 private static long lastTimestamp = -1L;
 // 0，并发控制
 private long sequence = 0L;
 
 private final long workerId;
 // 数据标识id部分
 private final long datacenterId;
 
 public IdWorker(){
 
 this.datacenterId = getDatacenterId(maxDatacenterId);
 this.workerId = getMaxWorkerId(datacenterId, maxWorkerId);
 }
 /**
 * @param workerId
 * 工作机器ID
 * @param datacenterId
 * 序列号
 */
 public IdWorker(long workerId, long datacenterId) {
 
 if (workerId > maxWorkerId || workerId < 0) {
 
 throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
 }
 if (datacenterId > maxDatacenterId || datacenterId < 0) {
 
 throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
 }
 this.workerId = workerId;
 this.datacenterId = datacenterId;
 }
 /**
 * 获取下一个ID
 *
 * @return
 */
 public synchronized long nextId() {
 
 long timestamp = timeGen();
 if (timestamp < lastTimestamp) {
 
 throw new RuntimeException(String.format("Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
 }
 
 if (lastTimestamp == timestamp) {
 
 // 当前毫秒内，则+1
 sequence = (sequence + 1) & sequenceMask;
 if (sequence == 0) {
 
 // 当前毫秒内计数满了，则等待下一秒
 timestamp = tilNextMillis(lastTimestamp);
 }
 } else {
 
 sequence = 0L;
 }
 lastTimestamp = timestamp;
 // ID偏移组合生成最终的ID，并返回ID
 long nextId = ((timestamp - twepoch) << timestampLeftShift)
 | (datacenterId << datacenterIdShift)
 | (workerId << workerIdShift) | 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();
 }
 
 /**
 * 
 * 获取 maxWorkerId
 * 
 */
 protected static long getMaxWorkerId(long datacenterId, long maxWorkerId) {
 
 StringBuffer mpid = new StringBuffer();
 mpid.append(datacenterId);
 String name = ManagementFactory.getRuntimeMXBean().getName();
 if (!name.isEmpty()) {
 
 /*
 * GET jvmPid
 */
 mpid.append(name.split("@")[0]);
 }
 /*
 * MAC + PID 的 hashcode 获取16个低位
 */
 return (mpid.toString().hashCode() & 0xffff) % (maxWorkerId + 1);
 }
 
 /**
 * 
 * 数据标识id部分
 * 
 */
 protected static long getDatacenterId(long maxDatacenterId) {
 
 long id = 0L;
 try {
 
 InetAddress ip = InetAddress.getLocalHost();
 NetworkInterface network = NetworkInterface.getByInetAddress(ip);
 if (network == null) {
 
 id = 1L;
 } else {
 
 byte[] mac = network.getHardwareAddress();
 id = ((0x000000FF & (long) mac[mac.length - 1])
 | (0x0000FF00 & (((long) mac[mac.length - 2]) << 8))) >> 6;
 id = id % (maxDatacenterId + 1);
 }
 } catch (Exception e) {
 
 System.out.println(" getDatacenterId: " + e.getMessage());
 }
 return id;
 }
 
 
 }

> 雪花算法的主键生成方案用在分布式场景下比较多，单机的话感觉就不太有必要，因为雪花算法生成的主键是固定位数的Long类型数据（比如上面代码生成的就是19位的主键），如果没有太大的数据量的 话，一方面浪费数据库资源，一方面前后端交互会有问题（js和java的序列化策略不一样，后端传long类型数据到前端会有精度丢失，只保留前17位数据）。所以如果不是很必要的话，还是用老实点的解决方案吧。