Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
try {
    conn = dataSource.getConnection();
    //關(guān)閉自動(dòng)提交
    conn.setAutoCommit(false);
    //SELECT ... FOR UPDATE是悲觀鎖的典型應(yīng)用，此時(shí)會(huì)鎖住被選中的行，其他事務(wù)無(wú)法更新這些行
    String sql = "SELECT * FROM product WHERE id = ? FOR UPDATE";
    ps = conn.prepareStatement(sql);
    ps.setInt(1, 1);
    rs = ps.executeQuery();
    if (rs.next()) {
        //獲取當(dāng)前庫(kù)存數(shù)量
        int count = rs.getInt("count");
        if (count > 0) {
            String updateSql = "UPDATE product SET count = count - 1 WHERE id = ?";
            ps = conn.prepareStatement(updateSql);
            ps.setInt(1, 1);
            ps.executeUpdate();
            conn.commit();
            System.out.println("扣減成功，剩余庫(kù)存：" + (count - 1));
        } else {
            System.out.println("庫(kù)存不足，扣減失敗");
        }
    }
} catch (Exception e) {
    if (conn != null) {
        try {
            //如果出現(xiàn)異常，進(jìn)行回滾
            conn.rollback();
        } catch (SQLException e1) {
            e1.printStackTrace();
        }
    }
    e.printStackTrace();
} finally {
    //在最后，關(guān)閉資源
    if (rs != null) {
        try {
            rs.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    if (ps != null) {
        try {
            ps.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    if (conn != null) {
        try {
            conn.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

import javax.persistence.*;
@Entity
@Data
public class Product {
    @Id
    @GeneratedValue
    private Long id;
    private Integer count;
    //版本號(hào)，用于實(shí)現(xiàn)樂觀鎖
    @Version
    private Integer version;
}

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
@Service
public class ProductService {
    @Autowired
    private ProductRepository productRepository;
    @Transactional
    public void reduceCount(Long productId) {
        //找到產(chǎn)品
        Product product = productRepository.findById(productId).get();
        //檢查庫(kù)存
        if (product.getCount() > 0) {
            //如果庫(kù)存足夠，減少庫(kù)存
            product.setCount(product.getCount() - 1);
            productRepository.save(product);
        } else {
            //庫(kù)存不足，拋出異常
            throw new RuntimeException("庫(kù)存不足");
        }
    }
}

// 使用 Redisson 庫(kù)實(shí)現(xiàn) Redis 分布式鎖
RedissonClient redisson = Redisson.create();
RLock lock = redisson.getLock("myLock");
try{
    lock.lock();
    // 執(zhí)行業(yè)務(wù)操作
}finally{
    lock.unlock();
}