Improve transaction state detection logic

[wanggang1111111]

When DataSourceUtils.getConnection(this.dataSource) creates a new connection,
this connection is automatically registered with Spring's TransactionSynchronizationManager.
Therefore, DataSourceUtils.isConnectionTransactional() returns true,
but in reality, this connection is newly created and should not be considered as a Spring-managed transactional connection.

Use TransactionSynchronizationManager.isActualTransactionActive() to check if there is an active Spring transaction.
Only when an active transaction exists should the connection be considered as a Spring-managed transactional connection.

This approach correctly distinguishes between newly created connections and genuine Spring-managed transactional connections.

[hazendaz]

@wanggang1111111 Please add back the line you deleted and remove the likely 'vim' command you stuck in that java doc.

[Copilot]

Pull request overview

This PR refines how SpringManagedTransaction determines whether a JDBC Connection should be treated as Spring-managed/transactional, by additionally requiring an actual active Spring transaction (to avoid misclassifying newly created, auto-registered connections).

Changes:

• Gate DataSourceUtils.isConnectionTransactional(...) behind TransactionSynchronizationManager.isActualTransactionActive().
• Minor formatting adjustments in openConnection() (plus a Javadoc line was modified).

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[coveralls]

coverage: 90.353% (+0.02%) from 90.335% — wanggang1111111:master into mybatis:master

[hazendaz]

The change is good but had copilot review the statements made. Its response was somewhat different and posting that below. Change is to be accepted.

The code change is accurate, but the explanation should be tightened slightly.
DataSourceUtils.getConnection() may bind a connection whenever transaction synchronization is active, and DataSourceUtils.isConnectionTransactional(...) can therefore return true even when there is no actual backing transaction (for example, synchronization-only scopes like PROPAGATION_SUPPORTS).

Using TransactionSynchronizationManager.isActualTransactionActive() in addition to isConnectionTransactional(...) correctly distinguishes a real transaction from synchronization-only participation.

So the implementation is correct; the only nuance is that the issue is broader than “newly created connections” and is really about “synchronization active without an actual transaction.”