嵌套@Transactional方法和@Async

Question

我将Spring与JPA一起使用。我打开了@EnableAsync和@EnableTransactionManahtml" target="_blank">gement。在我的用户注册服务方法中，我调用了一些其他服务方法，它们被注释为@Async。这些方法可以做各种事情，比如发送欢迎电子邮件和在我们的第三方支付系统中注册新创建的用户。

一切都很好，直到我想验证第三方支付系统是否成功创建了用户。此时，@Async方法试图创建一个UserAccount（引用新创建的User），并出现javax.persistence.EntityNotFoundException：无法找到ID为2017的com.dk.st.model.用户

寄存器调用如下所示：

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;
}

支付服务调用以完成其注册用户的工作，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);
}

这里列出的StackOverflow答案表明，我设置了一个新的传播，我已经完成了，但没有这样的运气。

有人能给我指出正确的方向吗？我真的不想直接从我的控制器方法调用paymentService。我觉得这肯定应该是一个服务级别的调用。

谢谢你的帮助！

Answer 1

尝试创建一个新的UserService类来管理用户检查，如下所示

@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;
}

然后在实际课堂上，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);

由

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

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

Answer 2

在Vyncent的帮助下，这是我得到的解决方案。我创建了一个名为UserCreationService的新类，并将所有处理User创建的方法都放在该类中。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，这个方法上没有事务注释。这是故意的。相应的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很清楚事务管理是问题所在。创建另一个服务让我能够更好地控制这些事务何时提交。虽然我最初对采取这种方法犹豫不决，但这是Spring托管事务和代理的权衡。

我希望这能帮助其他人节省一些时间。