Transactions via spring annotations - readonly or not?

Question

I've got in my project code similar to this

@Transactional(readOnly = true)
public void tt() {
    dd();
}

@Transactional()
public void dd() {
    gg();
}

@Transactional(readOnly = true)
public void gg() {

}

Function dd is used both by other readonly transaction functions and not readonly functions. Assuming that transaction should extendend from execution of tt to gg - operations in dd will in be read-only transaction or not?

Answer 1

In this particular example, your question is moot.

The call to dd() from tt() will not pass the proxy boundary so no transactional advise will be applied to dd() (since it's a call inside the same instance). Same with the call to gg() from dd(). Consequently, only the call from outside to tt() would actually be transaction-advised (in your case, with readOnly=true) and that would be the transaction that would be used in the entire call-chain.

In the general case though, read the documentation hinted by @melihcelik - it explains the behavior.

Answer 2

Spring's AbstractPlatformTransactionManager has a property named validateExistingTransaction that controls this behavior. Javadoc states that:

When participating in an existing transaction (e.g. with PROPAGATION_REQUIRES or PROPAGATION_SUPPORTS encountering an existing transaction), this outer transaction's characteristics will apply even to the inner transaction scope. Validation will detect incompatible isolation level and read-only settings on the inner transaction definition and reject participation accordingly through throwing a corresponding exception.

Since default propagation for Spring @Transactional annotation is REQUIRED and default validation strategy is false, I expect Spring to use existing transaction created from tt method call in readonly mode.

If you want to have a read only transaction, then you have to annotate your method with:

  @Transactional(propagation=Propagation.REQUIRES_NEW, readOnly=true)