我们如何在没有正在进行的交易的情况下拨打外部电话？

Question

We're using Spring & Hibernate in JBoss 4.2.3 and are calling an external system, which could take a while, as part of processing requests. To eliminate long-lived database locks we're not writing to our database until after the external call has returned. But Hibernate does not like being without a transaction so we have a read-only transaction, started by Spring, until we're doing our writes (in a new read-write subtransaction). Unfortunately this still means we're retaining resources during the external call, the allocated connection from the pool. Is there a way to make the external call without an ongoing transaction when the rest of the execution (before and after) needs one? Is there a better way of deferring the actual transaction until we really need it and still keep Hibernate happy?

Answer 1

Is it necessary to call the external system in your persistence layer? It seems more logical to do this kind of thing outside, before you hit persistence.

Answer 2

You actually don't need a transaction for reads.

Here is an example where the read call goes straight to the DAO object, but the write call is done within a transaction (using Spring's TransactionTemplate helper object):

public ContainerType getContainerType(Long id) {
    return this.containerTypeDao.getContainerType(id);
}

public Long saveContainerType(final ContainerType containerType) {
    return (Long) this.transactionTemplate.execute(new TransactionCallback() {

        public Long doInTransaction(TransactionStatus status) {
            try {
                return containerTypeDao.saveContainerType(containerType);
            }
            catch (Exception e) {
                status.setRollbackOnly();
                return null;
            }
        }
    });
}