基于悲观锁与独立计数表的分布式无间隙序列号生成方案

CREATE TABLE series_counter (
    series_id VARCHAR(50) PRIMARY KEY,
    current_counter BIGINT NOT NULL DEFAULT 1
);

-- 示例数据
INSERT INTO series_counter (series_id, current_counter) VALUES ('AA', 1);
INSERT INTO series_counter (series_id, current_counter) VALUES ('BB', 1);
-- ...以此类推

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.LockModeType;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Lock;
import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;
import org.springframework.stereotype.Service;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.transaction.annotation.Transactional;

// SeriesCounter 实体类示例
@Entity // 假设使用JPA
@Table(name = "series_counter")
class SeriesCounter {
    @Id
    private String seriesId; // 使用seriesId作为主键
    private Long currentCounter;

    // 构造函数、Getter、Setter (通常由Lombok @Data 或手动生成)
    public SeriesCounter() {}

    public SeriesCounter(String seriesId, Long currentCounter) {
        this.seriesId = seriesId;
        this.currentCounter = currentCounter;
    }

    public String getSeriesId() { return seriesId; }
    public void setSeriesId(String seriesId) { this.seriesId = seriesId; }
    public Long getCurrentCounter() { return currentCounter; }
    public void setCurrentCounter(Long currentCounter) { this.currentCounter = currentCounter; }

    public void incrementValue() {
        this.currentCounter++;
    }
}

// SeriesCounterRepository 接口示例
public interface SeriesCounterRepo extends JpaRepository<SeriesCounter, String> {

  @Lock(LockModeType.PESSIMISTIC_WRITE) // 施加悲观写锁
  // @Transactional // 某些特殊情况下，JPA仓库方法也可能需要此注解，但通常由调用方服务层事务管理
  @Query("SELECT sc FROM SeriesCounter sc WHERE sc.seriesId = :seriesId")
  SeriesCounter fetchLatest(@Param("seriesId") String seriesId);

}

// 业务逻辑服务类示例
@Service
public class DeviceNumberGeneratorService {

    @Autowired
    private SeriesCounterRepo seriesCounterRepo;

    // @Autowired
    // private SeriesRepository seriesRepo; // 假设有一个用于保存设备记录的Repository

    @Transactional // 确保整个操作在单个事务中完成
    public String generateDeviceNumber(String seriesId) {
        // 1. 获取并锁定当前系列的计数器
        // 此时，其他尝试获取相同seriesId的请求将被阻塞，直到当前事务完成
        SeriesCounter latestCounter = seriesCounterRepo.fetchLatest(seriesId);
        if (latestCounter == null) {
            // 处理系列不存在的情况，可能需要初始化或抛出异常
            throw new IllegalArgumentException("Series not found: " + seriesId);
        }

        Long currentNumber = latestCounter.getCurrentCounter();

        // 2. 构建新的设备编号（或设备记录）
        String newDeviceNumber = seriesId + "-" + String.format("%03d", currentNumber); // 示例格式化
        // 假设这里是创建并保存实际的设备记录
        // Series newSeriesRecord = new Series(seriesId, currentNumber, ...);
        // seriesRepo.save(newSeriesRecord);

        // 3. 递增计数器并保存
        latestCounter.incrementValue();
        seriesCounterRepo.save(latestCounter); // 更新计数器

        // 4. 返回生成的设备编号
        return newDeviceNumber;
    }
}