Grails withTransaction - why is it on a domain object?
We need to be able to rollback a complex transaction in the service without throwing an exception for the caller. I understand that the only way to achieve this is to use with Transaction.
The question arises:
- Why do I need to call this on a domain object like Books.withTransaction
- What if there is no corresponding domain object, which is a consequence of choosing a random one?
Below is more or less what I am trying to do. The use case is to withdraw from an account and put it on a credit card. If the transfer fails, we want to cancel the transaction, but not the payment record log, which should be recorded in a separate transaction (using RequiresNew). In any case, the service method should return a complex object, not an exception.
someService.groovy
Class SomeService {
@NotTransactional
SomeComplexObject someMethod() {
SomeDomainObject.withTransaction{ status ->
DomainObject ob1 = new DomainObject.save()
LogDomainObject ob2 = insertAndCommitLogInNewTransaction()
SomeComplexObject ob3 = someAction()
if (!ob3.worked) {
status.setRollbackOnly() // only rollback ob1, not ob2!
}
return ob3
}
}
}
The above is flawed - I am assuming "return ob3" will not return ob3 from the method as it does in the closure. Not sure how to communicate from within the closure to go beyond it.
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Into your main question, you can choose a random domain object if you like, it won't hurt. Or, if you like, you can find the current session and open a transaction instead:
grailsApplication.sessionFactory.currentSession.withTransaction { /* Do the things */ }
Stylistically, I have no preference here. Others can.
Not sure how to communicate from inside the closure to the outside.
In general, this can be difficult; withTransaction
can basically return whatever it wants, no matter what its closure argument returns. But it turns out that it withTransaction
returns the value returned by its closure. See here:
groovy> println(MyDomainObject.withTransaction { 2 + 2 })
4
By convention, all methods withFoo
that accept a closure should work in such a way that you can do what you are trying to do.
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