I have a springframework application in which I would like to add a transaction listener to a transaction which is currently in progress. The motivation is to trigger a post commit action which notifies downstream systems. I am using @Transactional to wrap a transaction around some service method -- which is where I want to create/register the post transaction listener. I want to do something "like" the following.
public class MyService {
@Transaction
public void doIt() {
modifyObjects();
// something like this
getTransactionManager().registerPostCommitAction(new
TransactionSynchronizationAdapter() {
public void afterCommit() {
notifyDownstream();
}
});
}
}
Spring has a TransactionSynchronization interface and adapter class which seems exactly what I want; however it is not immediately clear how to register one dynamically with either the current transaction, or the transaction manager. I would rather not subclass JtaTransactionManager if I can avoid it.
Q: Has anyone done this before.
Q: what is the simplest way to register my adapter?
Actually it was not as hard as I thought; spring has a static helper class that puts the 'right' stuff into the thread context.
TransactionSynchronizationManager.registerSynchronization(
new TransactionSynchronizationAdapter() {
@Override
public void afterCommit() {
s_logger.info("TRANSACTION COMPLETE!!!");
}
}
);
you could use an aspect to match transactional methods aspect in your service to accomplish this:
@Aspect
public class AfterReturningExample {
@AfterReturning("execution(* com.mypackage.MyService.*(..))")
public void afterReturning() {
// ...
}
}
Here is a more complete solution I did for a similar problem that with wanting my messages sent after transactions are committed (I could have used RabbitMQ TX but they are rather slow).
public class MessageBusUtils {
public static Optional<MessageBusResourceHolder> getTransactionalResourceHolder(TxMessageBus messageBus) {
if ( ! TransactionSynchronizationManager.isActualTransactionActive()) {
return Optional.absent();
}
MessageBusResourceHolder o = (MessageBusResourceHolder) TransactionSynchronizationManager.getResource(messageBus);
if (o != null) return Optional.of(o);
o = new MessageBusResourceHolder();
TransactionSynchronizationManager.bindResource(messageBus, o);
o.setSynchronizedWithTransaction(true);
if (TransactionSynchronizationManager.isSynchronizationActive()) {
TransactionSynchronizationManager.registerSynchronization(new MessageBusResourceSynchronization(o, messageBus));
}
return Optional.of(o);
}
private static class MessageBusResourceSynchronization extends ResourceHolderSynchronization<MessageBusResourceHolder, TxMessageBus> {
private final TxMessageBus messageBus;
private final MessageBusResourceHolder holder;
public MessageBusResourceSynchronization(MessageBusResourceHolder resourceHolder, TxMessageBus resourceKey) {
super(resourceHolder, resourceKey);
this.messageBus = resourceKey;
this.holder = resourceHolder;
}
@Override
protected void cleanupResource(MessageBusResourceHolder resourceHolder, TxMessageBus resourceKey,
boolean committed) {
resourceHolder.getPendingMessages().clear();
}
@Override
public void afterCompletion(int status) {
if (status == TransactionSynchronization.STATUS_COMMITTED) {
for (Object o : holder.getPendingMessages()) {
messageBus.post(o, false);
}
}
else {
holder.getPendingMessages().clear();
}
super.afterCompletion(status);
}
}
}
public class MessageBusResourceHolder extends ResourceHolderSupport {
private List<Object> pendingMessages = Lists.newArrayList();
public void addMessage(Object message) {
pendingMessages.add(message);
}
protected List<Object> getPendingMessages() {
return pendingMessages;
}
}
Now in your class where you actually send the message you will do
@Override
public void postAfterCommit(Object o) {
Optional<MessageBusResourceHolder> holder = MessageBusTxUtils.getTransactionalResourceHolder(this);
if (holder.isPresent()) {
holder.get().addMessage(o);
}
else {
post(o, false);
}
}
Sorry for the long winded coding samples but hopefully that will show someone how to do something after a commit.
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