深入讲解基于Java开发的借据锁

@Table(name = "asset_loan_invoice_lock_info")
@Getter
@Setter
@EqualsAndHashCode(callSuper = true)
@ToString(callSuper = true)
public class AssetLoanInvoiceLockInfoDo extends AssetLoanInvoiceLockInfoKeyDo implements Serializable {
    private static final long serialVersionUID = 1101362594517114915L;
    /**
     * 借据锁锁状态 EnumBool 0-否 1-是
     */
    @Column(name = "lock_status")
    private String lockStatus;
    /**
     * 锁定流水
     */
    @Column(name = "lock_serial_no")
    private String lockSerialNo;
    /**
     * 锁定交易码
     */
    @Column(name = "lock_trade_code")
    private String lockTradeCode;
    /**
     * 锁定交易描述
     */
    @Column(name = "lock_trade_description")
    private String lockTradeDescription;
    /**
     * 乐观锁版本
     */
    @Column(name = "lock_version")
    private Integer lockVersion;
    /**
     * 创建时间
     */
    @Column(name = "create_time")
    private java.util.Date createTime;
    /**
     * 更新时间
     */
    @Column(name = "update_time")
    private java.util.Date updateTime;
    /**
     * 锁定时间
     */
    @Column(name = "lock_time")
    private java.util.Date lockTime;
}

/**
 * 加锁方法：通过数据库UPDATE的原子性保证不会重复加锁
 * @param loanId 借据ID
 * @param tradeCode 交易码
 * @param serialNo 流水号
 * @return true=加锁成功，false=已被锁定
 */
public boolean lockLoanInvoice(String loanId, String tradeCode, String serialNo) {
    // 1. 先查询当前锁信息（获取旧版本号）
    AssetLoanInvoiceLockInfoDo lockInfo = lockInfoMapper.selectByLoanId(loanId);
    if (lockInfo == null) {
        // 首次加锁，初始化记录
        lockInfo = new AssetLoanInvoiceLockInfoDo();
        lockInfo.setLoanId(loanId);
        lockInfo.setLockStatus("1");
        lockInfo.setLockSerialNo(serialNo);
        lockInfo.setLockTradeCode(tradeCode);
        lockInfo.setLockVersion(1);
        lockInfo.setLockTime(new Date());
        lockInfoMapper.insert(lockInfo);
        return true;
    }
    
    // 2. 原子更新：带版本号+锁状态条件
    int updateCount = lockInfoMapper.updateLockStatus(
        loanId, 
        "0",          // 原状态：未锁定
        lockInfo.getLockVersion(), // 原版本号
        "1",          // 新状态：锁定
        serialNo,
        tradeCode,
        new Date()
    );
    
    // 3. 只有更新成功（影响行数=1），才代表加锁成功
    return updateCount == 1;
}

<update id="updateLockStatus">
    UPDATE asset_loan_invoice_lock_info
    SET lock_status = #{newLockStatus},
        lock_serial_no = #{serialNo},
        lock_trade_code = #{tradeCode},
        lock_time = #{lockTime},
        lock_version = lock_version + 1,
        update_time = NOW()
    WHERE loan_id = #{loanId}
      AND lock_status = #{oldLockStatus}
      AND lock_version = #{oldVersion}
</update>

public boolean unlockLoanInvoice(String loanId, String serialNo) {
    int updateCount = lockInfoMapper.updateUnlockStatus(
        loanId,
        "1",          // 原状态：已锁定
        serialNo,     // 必须是加锁时的流水号
        "0"           // 新状态：未锁定
    );
    return updateCount == 1;
}

/**
 * 定时任务：解锁超过30分钟的借据锁
 */
@Scheduled(fixedRate = 5 * 60 * 1000) // 每5分钟执行一次
public void unlockTimeoutLock() {
    // 计算超时时间：当前时间 - 30分钟
    Date timeoutTime = new Date(System.currentTimeMillis() - 30 * 60 * 1000);
    // 只解锁超时且未解锁的锁
    lockInfoMapper.unlockTimeoutLock(timeoutTime);
}

<update id="unlockTimeoutLock">
    UPDATE asset_loan_invoice_lock_info
    SET lock_status = '0',
        lock_serial_no = '',
        lock_trade_code = '',
        lock_version = lock_version + 1,
        update_time = NOW()
    WHERE lock_status = '1'
      AND lock_time < #{timeoutTime}
</update>