Delaying sending of mail until transaction commits

Does anyone have a good tuto开发者_运维问答rial or some advice on how to implement one's own XAResource? I need Spring's MailSender to be transactional, so that the mail will only be sent once the transaction commits, and it seems there isn't any existing transactional wrapper.

If you just need to wait for the commit, as you say in a comment, you can investigate using TransactionSynchronizationManager.registerSynchronization() to trigger email sending on commit.

You can use a TransactionSynchronizationManager.registerSynchronization (like gpeche mentioned) with a TransactionSynchronizationAdapter which has a variety of methods that are called at various stages of the current transaction. I think the most suitable method for the question is the afterCommit.

TransactionSynchronizationManager.registerSynchronization(new TransactionSynchronizationAdapter() {
    @Override
    public void afterCommit() {
        super.afterCommit();
        sendEmail();
    }
});

I doubt that it's possible to implement true XAResource for SMTP. There should be transaction support on the resource manager (SMTP server in this case) and I don't believe there are any. I would say your best bet is 'Last resource commit' pattern - which allows one non XA resource participate in XA transaction. Search Google, there are plenty of info. Most Java EE servers supports this.

One other option next to the one mentioned by gpeche, is sending a transactional JMS message from within the transaction. Then let the message listener (like e.g. a MDB bean) send the email.

Another trick in EJB is scheduling a timer from within a transaction. The timer is also transactional and will only be started when the transaction commits. Simply use a timer with timeout = 0, so it will start immediately after the transaction commits.