mybatis雪花算法id

MyBatis本身并没有提供雪花算法生成ID的功能，但你可以在使用MyBatis时结合其他工具来实现雪花算法生成ID。

雪花算法是一种分布式唯一ID生成算法，可以用于生成全局唯一的ID，具有高性能和高可用性。它的生成规则一般包括时间戳、数据中心ID、机器ID和序列号等信息。

你可以通过使用Java的Snowflake算法实现类来生成雪花算法ID。下面是一个简单的示例：

public class SnowflakeIdGenerator {
    private static final long START_TIMESTAMP = 1609430400000L; // 设置一个起始时间戳，建议使用项目启用时间
    private static final long DATA_CENTER_ID_BITS = 5L; // 数据中心ID位数
    private static final long MACHINE_ID_BITS = 5L; // 机器ID位数
    private static final long SEQUENCE_BITS = 12L; // 序列号位数

    private static final long MAX_DATA_CENTER_ID = ~(-1L << DATA_CENTER_ID_BITS);
    private static final long MAX_MACHINE_ID = ~(-1L << MACHINE_ID_BITS);

    private final long dataCenterId;
    private final long machineId;
    private long sequence = 0L;
    private long lastTimestamp = -1L;

    public SnowflakeIdGenerator(long dataCenterId, long machineId) {
        if (dataCenterId > MAX_DATA_CENTER_ID || dataCenterId < 0) {
            throw new IllegalArgumentException("Data center ID can't be greater than " + MAX_DATA_CENTER_ID + " or less than 0");
        }
        if (machineId > MAX_MACHINE_ID || machineId < 0) {
            throw new IllegalArgumentException("Machine ID can't be greater than " + MAX_MACHINE_ID + " or less than 0");
        }
        this.dataCenterId = dataCenterId;
        this.machineId = machineId;
    }

    public synchronized long generateId() {
        long currentTimestamp = System.currentTimeMillis();
        if (currentTimestamp < lastTimestamp) {
            throw new RuntimeException("Clock moved backwards. Refusing to generate ID for " + (lastTimestamp - currentTimestamp) + " milliseconds");
        }

        if (currentTimestamp == lastTimestamp) {
            sequence = (sequence + 1) & ((1 << SEQUENCE_BITS) - 1);
            if (sequence == 0) {
                currentTimestamp = tillNextMillis(lastTimestamp);
            }
        } else {
            sequence = 0L;
        }

        lastTimestamp = currentTimestamp;

        return ((currentTimestamp - START_TIMESTAMP) << (DATA_CENTER_ID_BITS + MACHINE_ID_BITS + SEQUENCE_BITS))
                | (dataCenterId << (MACHINE_ID_BITS + SEQUENCE_BITS))
                | (machineId << SEQUENCE_BITS)
                | sequence;
    }

    private long tillNextMillis(final long lastTimestamp) {
        long timestamp = System.currentTimeMillis();
        while (timestamp <= lastTimestamp) {
            timestamp = System.currentTimeMillis();
        }
        return timestamp;
    }
}

在使用MyBatis时，你可以将上述的SnowflakeIdGenerator作为一个工具类，用来生成唯一ID。在插入数据时，调用该工具类的generateId方法生成ID，并设置到对应的实体类中。

public interface UserMapper {
    void insert(User user);
}

public class UserService {
    private final UserMapper userMapper;
    private final SnowflakeIdGenerator idGenerator;

    public UserService(UserMapper userMapper, SnowflakeIdGenerator idGenerator) {
        this.userMapper = userMapper;
        this.idGenerator = idGenerator;
    }

    public void addUser(User user) {
        long id = idGenerator.generateId();
        user.setId(id);
        userMapper.insert(user);
    }
}

这样，就可以在使用MyBatis插入数据时生成雪花算法ID了。当然，你可以根据自己的需求进行一些定制化改造。