回答

这个示例代码是一个简单的订单撮合交易系统，基于Spring Boot和Spring Data JPA，演示了订单的创建、撮合和交易记录的生成：

// 实体类
@Entity
public class Order {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    private Long userId;
    private String type; // "BUY" or "SELL"
    private BigDecimal price;
    private int quantity;
    private boolean matched;
    // ...其他字段、Getter和Setter
}

@Entity
public class Trade {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    
    private Long buyerId;
    private Long sellerId;
    private BigDecimal price;
    private int quantity;
    private LocalDateTime tradeTime;
    // ...其他字段、Getter和Setter
}

// 仓库接口
public interface OrderRepository extends JpaRepository<Order, Long> {
    List<Order> findByTypeAndMatchedOrderByPriceAsc(String type, boolean matched);
}

public interface TradeRepository extends JpaRepository<Trade, Long> {
}

// 服务类
@Service
public class TradingService {
    @Autowired
    private OrderRepository orderRepository;
    
    @Autowired
    private TradeRepository tradeRepository;
    
    @Transactional
    public void createOrder(Order order) {
        orderRepository.save(order);
        matchOrders(order);
    }
    
    private void matchOrders(Order newOrder) {
        List<Order> oppositeOrders;
        if ("BUY".equals(newOrder.getType())) {
            oppositeOrders = orderRepository.findByTypeAndMatchedOrderByPriceAsc("SELL", false);
        } else {
            oppositeOrders = orderRepository.findByTypeAndMatchedOrderByPriceDesc("BUY", false);
        }
        
        for (Order oppositeOrder : oppositeOrders) {
            if (oppositeOrder.getPrice().compareTo(newOrder.getPrice()) == 0) {
                int quantity = Math.min(oppositeOrder.getQuantity(), newOrder.getQuantity());
                createTrade(oppositeOrder.getUserId(), newOrder.getUserId(), oppositeOrder.getPrice(), quantity);
                updateOrdersMatchedStatus(oppositeOrder, newOrder, quantity);
            }
        }
    }
    
    private void createTrade(Long buyerId, Long sellerId, BigDecimal price, int quantity) {
        Trade trade = new Trade();
        trade.setBuyerId(buyerId);
        trade.setSellerId(sellerId);
        trade.setPrice(price);
        trade.setQuantity(quantity);
        trade.setTradeTime(LocalDateTime.now());
        tradeRepository.save(trade);
    }
    
    private void updateOrdersMatchedStatus(Order... orders) {
        for (Order order : orders) {
            order.setMatched(true);
            orderRepository.save(order);
        }
    }
}