阿里技术专家殷浩详解DDD系列 代码实践
- DP是一个传统意义上的Value Object,拥有Immutable的特性
- DP是一个完整的概念整体,拥有精准定义
- DP使用业务域中的原生语言
- DP可以是业务域的最小组成部分、也可以构建复杂组合
- 让隐性的概念显性化
- 让隐性的上下文显性化
- 封装多对象行为
二:应用架构
public class TransferController {
private TransferService transferService;
public Result<Boolean> transfer(String targetAccountNumber, BigDecimal amount, HttpSession session) {
Long userId = (Long) session.getAttribute("userId");
return transferService.transfer(userId, targetAccountNumber, amount, "CNY");
}
}
public class TransferServiceImpl implements TransferService {
private static final String TOPIC_AUDIT_LOG = "TOPIC_AUDIT_LOG";
private AccountMapper accountDAO;
private KafkaTemplate<String, String> kafkaTemplate;
private YahooForexService yahooForex;
@Override
public Result<Boolean> transfer(Long sourceUserId, String targetAccountNumber, BigDecimal targetAmount, String targetCurrency) {
// 1. 从数据库读取数据,忽略所有校验逻辑如账号是否存在等
AccountDO sourceAccountDO = accountDAO.selectByUserId(sourceUserId);
AccountDO targetAccountDO = accountDAO.selectByAccountNumber(targetAccountNumber);
// 2. 业务参数校验
if (!targetAccountDO.getCurrency().equals(targetCurrency)) {
throw new InvalidCurrencyException();
}
// 3. 获取外部数据,并且包含一定的业务逻辑
// exchange rate = 1 source currency = X target currency
BigDecimal exchangeRate = BigDecimal.ONE;
if (sourceAccountDO.getCurrency().equals(targetCurrency)) {
exchangeRate = yahooForex.getExchangeRate(sourceAccountDO.getCurrency(), targetCurrency);
}
BigDecimal sourceAmount = targetAmount.divide(exchangeRate, RoundingMode.DOWN);
// 4. 业务参数校验
if (sourceAccountDO.getAvailable().compareTo(sourceAmount) < 0) {
throw new InsufficientFundsException();
}
if (sourceAccountDO.getDailyLimit().compareTo(sourceAmount) < 0) {
throw new DailyLimitExceededException();
}
// 5. 计算新值,并且更新字段
BigDecimal newSource = sourceAccountDO.getAvailable().subtract(sourceAmount);
BigDecimal newTarget = targetAccountDO.getAvailable().add(targetAmount);
sourceAccountDO.setAvailable(newSource);
targetAccountDO.setAvailable(newTarget);
// 6. 更新到数据库
accountDAO.update(sourceAccountDO);
accountDAO.update(targetAccountDO);
// 7. 发送审计消息
String message = sourceUserId + "," + targetAccountNumber + "," + targetAmount + "," + targetCurrency;
kafkaTemplate.send(TOPIC_AUDIT_LOG, message);
return Result.success(true);
}
}