使用@Async 嵌套@Transactional 方法

Question

我在 JPA 中使用 Spring。我打开了@EnableAsync 和@EnableTransactionManagement。在我的用户注册服务方法中，我调用了一些其他的服务方法，它们被注释为@Async。这些方法可以做各种各样的事情，比如发送欢迎电子邮件和使用我们的第三方支付系统注册新创建的用户。

在我想验证第三方支付系统是否成功创建用户之前，一切正常。此时，@Async 方法会尝试创建一个 UserAccount（它引用新生成的 User）并返回 javax.persistence.EntityNotFoundException: Unable to find com.dk.st.model.User with id 2017 错误

注册调用如下所示：

private User registerUser(User newUser, Boolean waitForAccount) {
    String username = newUser.getUsername();
    String email = newUser.getEmail();

    // ... Verify the user doesn't already exist

    // I have tried all manner of flushing and committing right here, nothing works
    newUser = userDAO.merge(newUser);

    // Here is where we register the new user with the payment system.
    // The User we just merged is not /actually/ in the DB
    Future<Customer> newCustomer = paymentService.initializeForNewUser(newUser);
    // Here is where I occasionally (in test methods) pause this thread to wait
    // for the successful account creation.
    if (waitForAccount) {
        try {
            newCustomer.get();
        } catch (Exception e) {
            logger.error("Exception while creating user account!", e);
        }
    }

    // Do some other things that may or may not be @Aysnc

    return newUser;
}

支付服务调用它来完成注册用户的工作，如下所示：

@Async
@Override
@Transactional(propagation = Propagation.REQUIRES_NEW)
public Future<Customer> initializeForNewUser(User newUser) {
    // ... Set up customerParams

    Customer newCustomer = null;
    try {
        newCustomer = Customer.create(customerParams);

        UserAccount newAccount = new UserAccount();
        newAccount.setUser(newUser);
        newAccount.setCustomerId(newCustomer.getId());
        newAccount.setStatus(AccountStatus.PRE_TRIAL);

        // When merging, JPA cannot find the newUser object in the DB and complains
        userAccountDAO.merge(newAccount);
    } catch (Exception e) {
        logger.error("Error while creating UserAccount!", e);
        throw e;
    }

    return new AsyncResult<Customer>(newCustomer);
}

列出 here 的 StackOverflow 答案表明我设置了 REQUIRES_NEW 传播，我已经这样做了，但没有这样的运气。

谁能指出我正确的方向？我真的不想直接从我的控制器方法调用 paymentService 。我觉得这肯定是服务级别的调用。

感谢您的帮助！

Answer 1

在 Vyncent 的帮助下，这是我得出的解决方案。我创建了一个名为UserCreationService 的新类，并将处理User 创建的所有方法都放在该类中。这是一个例子：

@Override
public User registerUserWithProfileData(User newUser, String password, Boolean waitForAccount) {
    newUser.setPassword(password);
    newUser.encodePassword();
    newUser.setJoinDate(Calendar.getInstance(TimeZone.getTimeZone("UTC")).getTime());

    User registered = userService.createUser(newUser);
    registered = userService.processNewRegistration(registered, waitForAccount);

    return userService.setProfileInformation(registered);
}

您会注意到此方法上有 NO @Transactional 注释。这是故意的。对应的createUser 和processNewRegistration 定义如下所示：

@Override
@Transactional(propagation = Propagation.REQUIRES_NEW)
public User createUser(User newUser) {
    String username = newUser.getUsername();
    String email = newUser.getEmail();

    if ((username != null) && (userDAO.getUserByUsername(username) != null)) {
        throw new EntityAlreadyExistsException("User already registered: " + username);
    }

    if (userDAO.getUserByUsername(newUser.getEmail()) != null) {
        throw new EntityAlreadyExistsException("User already registered: " + email);
    }

    return userDAO.merge(newUser);
}

@Override
@Transactional(propagation = Propagation.REQUIRES_NEW)
public User processNewRegistration(
        User newUser,
        Boolean waitForAccount) 
{
    Future<UserAccount> customer = paymentService.initializeForNewUser(newUser);
    if (waitForAccount) {
        try {
            customer.get();
        } catch (Exception e) {
            logger.error("Error while creating Customer object!", e);
        }
    }

    // Do some other maintenance type things...

    return newUser;
}

Vyncent 发现事务管理是问题所在。创建其他服务使我能够更好地控制这些事务何时提交。虽然我最初对采用这种方法犹豫不决，但这是与 Spring 托管事务和代理的权衡。

我希望这可以帮助其他人在以后节省一些时间。

Answer 2

尝试创建一个新的 UserService 类来管理用户检查，就像这样

@Override
@Transactional(propagation = Propagation.REQUIRES_NEW)
public User createOrUpdateUser(User newUser) {
    String username = newUser.getUsername();
    String email = newUser.getEmail();

    // ... Verify the user doesn't already exist

    // I have tried all manner of flushing and committing right here, nothing works
    newUser = userDAO.merge(newUser);
    return newUser;
}

然后在实际的类中，改变

private User registerUser(User newUser, Boolean waitForAccount) {
    String username = newUser.getUsername();
    String email = newUser.getEmail();

    // ... Verify the user doesn't already exist

    // I have tried all manner of flushing and committing right here, nothing works
    newUser = userDAO.merge(newUser);

通过

private User registerUser(User newUser, Boolean waitForAccount) {
    newUser = userService.createOrUpdateUser(newUser);

带有 @Transactional REQUIRES_NEW 的新用户服务应该强制提交并解决问题。