public class DistributedLock {
    private DataSource dataSource;
    private Connection connection;
    public void acquireLock() {
        try {
            connection = dataSource.getConnection();
            // 在數(shù)據(jù)庫(kù)中插入一行記錄來(lái)獲取鎖
            // ...
        } catch (SQLException e) {
            throw new RuntimeException("Failed to acquire lock", e);
        }
    }
    public void releaseLock() {
        try {
            // 在數(shù)據(jù)庫(kù)中刪除該行記錄來(lái)釋放鎖
            // ...
        } catch (SQLException e) {
            throw new RuntimeException("Failed to release lock", e);
        } finally {
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    throw new RuntimeException("Failed to close connection", e);
                }
            }
        }
    }
}

public class DistributedLock {
    private Cache cache;
    public void acquireLock() {
        boolean acquired = cache.setnx("lock_key", "holder", 60);
        if (!acquired) {
            throw new RuntimeException("Failed to acquire lock");
        }
    }
    public void releaseLock() {
        cache.del("lock_key");
    }
}

public class IdGenerator {
    private DataSource dataSource;
    private Connection connection;
    public String generateId() {
        try {
            connection = dataSource.getConnection();
            // 查詢當(dāng)前最大的ID值
            // ...
            // 生成新的ID
            // ...
            // 更新最大ID值
            // ...
        } catch (SQLException e) {
            throw new RuntimeException("Failed to generate ID", e);
        } finally {
            if (connection != null) {
                try {
                    connection.close();
                } catch (SQLException e) {
                    throw new RuntimeException("Failed to close connection", e);
                }
            }
        }
    }
}

public class IdGenerator {
    private long workerId;
    private long sequence = 0L;
    private long lastTimestamp = -1L;
    public synchronized String generateId() {
        long timestamp = System.currentTimeMillis();
        if (timestamp < lastTimestamp) {
            throw new RuntimeException("Invalid system clock");
        }
        if (timestamp == lastTimestamp) {
            sequence = (sequence + 1) & 4095;
            if (sequence == 0) {
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            sequence = 0;
        }
        lastTimestamp = timestamp;
        long id = ((timestamp - epoch) << 22) | (workerId << 12) | sequence;
        return String.valueOf(id);
    }
    private long tilNextMillis(long lastTimestamp) {
        long timestamp = System.currentTimeMillis();
        while (timestamp <= lastTimestamp) {
            timestamp = System.currentTimeMillis();
        }
        return timestamp;
    }
}

public class OrderService {
    private MessageProducer producer;
    public void createOrder(String userId, String productId) {
        try {
            // 創(chuàng)建訂單
            String orderId = IdGenerator.generateId();
            Order order = new Order(orderId, userId, productId);
            order.save();
            // 扣減庫(kù)存
            Inventory inventory = InventoryService.getInventory(productId);
            inventory.decreaseStock();
            inventory.save();
            // 發(fā)送訂單創(chuàng)建消息
            producer.sendOrderCreatedMessage(order);
        } catch (Exception e) {
            // 發(fā)送訂單創(chuàng)建失敗消息
            producer.sendOrderCreateFailedMessage(userId, productId);
            throw new RuntimeException("Failed to create order", e);
        }
    }
}

public class OrderService {
    private XADataSource dataSource;
    public void createOrder(String userId, String productId) {
        try {
            XAConnection connection = dataSource.getXAConnection();
            XAResource xaResource = connection.getXAResource();
            // 開(kāi)始分布式事務(wù)
            xaResource.start(xid, XAResource.TMNOFLAGS);
            // 創(chuàng)建訂單
            String orderId = IdGenerator.generateId();
            Order order = new Order(orderId, userId, productId);
            order.save();
            // 扣減庫(kù)存
            Inventory inventory = InventoryService.getInventory(productId);
            inventory.decreaseStock();
            inventory.save();
            // 提交分布式事務(wù)
            xaResource.end(xid, XAResource.TMSUCCESS);
            xaResource.prepare(xid);
            xaResource.commit(xid, true);
        } catch (Exception e) {
            // 回滾分布式事務(wù)
            xaResource.rollback(xid);
            throw new RuntimeException("Failed to create order", e);
        }
    }
}