fix: extend OSIV to manage sessions for all datasources

[jamesfredley]

Summary

Fixes #14333 and #11798 - both have the same root cause.

GrailsOpenSessionInViewInterceptor only registered a session for the default datasource's SessionFactory. Calling withSession on a secondary datasource during a web request threw No Session found for current thread because no session was bound for that SessionFactory in TransactionSynchronizationManager.

Root Cause

In HibernateDatastoreSpringInitializer (lines 189-194), only one OSIV interceptor is created referencing hibernateDatastore (the default). The interceptor's setHibernateDatastore() called setSessionFactory(hibernateDatastore.getSessionFactory()) - binding only the default SessionFactory.

Call chain for #14333:

1. GormEntity.withSession -> AbstractHibernateGormStaticApi.withSession
2. -> AbstractHibernateDatastore.withSession -> getHibernateTemplate().execute(callable)
3. -> GrailsHibernateTemplate.doExecute -> getSession() -> sessionFactory.getCurrentSession()
4. -> GrailsSessionContext.currentSession() checks TransactionSynchronizationManager.getResource(sessionFactory) for the secondary SessionFactory
5. -> Nothing bound because OSIV only registered for default -> No Session found

#11798 has the same root cause: domain class mapped to non-default datasource used as command object fails validation because validate() needs a session but OSIV never opened one.

Fix

Modified GrailsOpenSessionInViewInterceptor to handle multiple datasource SessionFactory instances in a single interceptor:

• setHibernateDatastore() now iterates all connection sources from HibernateDatastore and stores non-default datasource SessionFactory references in an additionalSessionFactories list
• preHandle() opens sessions and binds SessionHolder to TransactionSynchronizationManager for each additional datasource (skipping any that already have a session bound)
• postHandle() flushes additional sessions if their flush mode warrants it
• afterCompletion() unbinds and closes additional sessions in reverse order

This approach keeps a single interceptor bean (backward compatible) and avoids the complexity of registering per-datasource OSIV beans.

Tests

Unit Tests (5 tests)

• MultiDataSourceSessionSpec - Tests OSIV interceptor directly:
  • Default datasource session binding
  • Secondary datasource session binding
  • Cleanup of all datasource sessions
  • Skip-if-already-bound behavior
  • CRUD operations on secondary datasource

Functional/Integration Tests (4 tests via HTTP)

• MultiDataSourceWithSessionSpec - Tests through actual HTTP requests to a controller:
  • withSession on secondary datasource does not throw (covers Grails7 - Multi DB withSession does not work #14333)
  • CRUD via withSession on secondary datasource
  • Domain validation via withSession on secondary datasource (covers Problem With Multiple Datasources #11798)
  • withSession works after executeUpdate on secondary datasource

Existing Tests

• All 10 grails-data-hibernate5 tests pass
• All 42 grails-data-hibernate5-core connection tests pass
• All 6 existing grails-multiple-datasources integration tests pass

Changed Files

File	Change
GrailsOpenSessionInViewInterceptor.java	Multi-datasource OSIV support
grails-data-hibernate5/grails-plugin/build.gradle	Added servlet-api test dependency
MultiDataSourceSessionSpec.groovy	New unit tests
SecondaryBookController.groovy	New test controller
UrlMappings.groovy	URL mappings for test controller
MultiDataSourceWithSessionSpec.groovy	New functional tests via HTTP
grails-multiple-datasources/build.gradle	Added HTTP client + URL mappings dependencies

[Copilot]

Pull request overview

This pull request fixes a critical issue where GrailsOpenSessionInViewInterceptor only managed sessions for the default datasource, causing "No Session found for current thread" errors when using withSession on secondary datasources during web requests (issues #14333 and #11798).

Changes:

• Extended GrailsOpenSessionInViewInterceptor to discover and manage sessions for all configured datasources, not just the default
• Added comprehensive unit tests directly testing the interceptor's multi-datasource session management
• Added functional integration tests that verify the fix through HTTP requests to a controller using secondary datasource operations

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
GrailsOpenSessionInViewInterceptor.java	Core fix: extends OSIV to iterate all connection sources and open/bind/close sessions for each non-default datasource alongside the default
grails-plugin/build.gradle	Added servlet-api test dependency for unit tests
MultiDataSourceSessionSpec.groovy	New unit tests verifying session binding, cleanup, skip-if-bound behavior, and CRUD operations
SecondaryBookController.groovy	Test controller providing endpoints for functional validation of withSession, validation, and executeUpdate scenarios
UrlMappings.groovy	URL mappings to route requests to test controller
MultiDataSourceWithSessionSpec.groovy	Integration tests exercising the fix via HTTP to verify both reported issues are resolved
grails-multiple-datasources/build.gradle	Added HTTP client and URL mappings dependencies for functional tests

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[jdaugherty]

Looks like this has some legitimate test failures

[jdaugherty]

I think this makes sense, but we need another reviewer for this one given the potential for impact.

[davydotcom]

Test line up with what would happen in a real world scenario. This has been broken a while I dont think we often use multi datasource in a project. But it makes sense that these should be activated in that scenario.