Endless loop with DataSourceUtils in spring-jdbc

[drachenpalme]

DataSourceUtils resolution getTargetConnection gets stuck in an endless loop under certain conditions in spring-jdbc 6.2.2/6.2.3.

I am creating a DataSource, wrapping it into the TransactionAwareDataSourceProxy and then creating an EntityManagerFactory. Then the datasource and the emf both get posted to a JpaTransactionManager.
Upon trying to commit a transaction, the application goes into an endless loop in DataSourceUtils.getTargetConnection().

As far as I could understand it by debugging, the following happens.
TransactionAwareDataSourceProxy gets asked for a connection and creates a lazy initialization proxy. As this proxy is lazy, it does not initialize an inner. The proxy handler is the TransactionAwareInvocationHandler.

Next step is, that this proxy gets bound to the current transaction-context in the TransactionSynchronizationManager. This happens during JpaTransactionManager.doBegin(Object, TransactionDefinition).

Now, during release of the connection while committing, the connection proxy gets into DataSourceUtils.getTargetConnection() and there it is determined, it is an instanceof ConnectionProxy and therefore gets resolved within TransactionAwareDataSourceProxy, which delegates to DataSourceUtils.doGetConnection, which delegates to TransactionSynchronizationManager.getResource which returns the uninitialized proxy.

I am not quite sure, why most invocations do not trigger this issue and some do. My current assumption is, that there is no issue, as long as the databaseconnection is actually used within the transaction. We have, however, cases, where a spring bean caches data, requests a transaction but does not actually trigger database queries upon cache-hits.

I am not quite sure, how to solve this correctly. Probably a non-initialized proxy for a connection should not be registered at all within the TransactionAwareDataSourceProxy?

[sbrannen]

DataSourceUtils resolution getTargetConnection gets stuck in an endless loop under certain conditions in spring-jdbc 6.2.2/6.2.3.

Are you claiming that this is a regression that did not occur before Spring Framework 6.2.2?

In any case, can you please provide a small sample application that reproduces the problem (preferably something that we can download and run, such as a public Git repository or a ZIP file attached to this issue)?

Thanks

[drachenpalme]

Sorry, I didn't make that clear. It occurs both in 6.2.2 and 6.2.3, I have not tested other versions.
I will try to create a sample app.

[drachenpalme]

Hi Sam,

I managed to distill the issue into a mini-project here:
https://github.com/drachenpalme/spring_ticket_34484

Upon executing Main.main you will first enter the TransactionalBean#doWithDb(), which actually does trigger unproxying the javax.sql.Connection prior to the doCommit() and therefore behaves as expected.
It will then enter TransactionalBean#doWithoutDb(), which will immediately return, not unproxying the Connection and therefor triggering the issue.

Please let me know, if you need further help or info. As I said, as I do not understand the concepts within the spring code, I am not sure, what the best way to solve this is. My assumption would be, DataSouerceUtils#doReleaseConnection should be made aware, if a connection is completely unused.
Maybe ConnectionHolder.hasConnection should be more like ConnectionHolder.hasActiveConnection and that should check, whether the connectionHandle is a non-initialized proxy?