如何在执行长任务之前完成容器管理的事务？

Question

I have a task which consists of 3 steps prepare , execute , update . prepare and update need to work within a transaction, whereas execute takes very long (ie several minutes up to hours). The task is part of an EJB, ie:

@Stateless
public class Task {
    public void doTask() {
        prepare();
        execute();
        update();
    }
}

My question is, is there an (elegant) way to commit and finish the transaction after prepare and start a new one before update ? I'd rather use container-managed transactions and possibly not switch to use UserTransaction .

It is possible to split the tasks into single EJBs if it gains any advantage, but note that suspending the transaction for execute (ie using @Transactional(TxType.NOT_SUPPORTED) is not enough since this still triggers the timeout.

I tried to split it into a TaskExecute class which has @Asynchronous @Transactional(NOT_SUPPORTED) public void execute() and sending an event when done. But this doesn't seem to work either.

Is there a way to do this?

---

After some further testing let me conclude: Alexanders reply was absolutely correct. My understanding had to be altered. Foremost, I wasn't aware that @Transactional does not work on EJBs, but only on CDI beans. For EJBs the annotation is called @TransactionAttribute and can be set to basically the same values. A combination of @Asynchronous and @TransactionAttribute(NOT_SUPPORTED) does work (if not waiting for the result).

Answer 1

It depends on the version of Java EE you want to use. Here are three possible solutions.

• use JMS, send an appropriate message and do the execute in the MDB (any version, but full profile required)
• use Java EE 6.0's Timer Service and schedule a task to perform the execute asynchronously ( @Timeout )
• use Java EE 7.0's Batch Processing API to schedule a proper long running batch job.

The latter is probably what you are looking for, but only available in Java EE 7.0 and up. Otherwise, the JMS solutions is the cleanest, but if JMS is not an option, the Timer Service should work.