HibernateJpaDialect logs warning in case of Connection mismatch (e.g. configured release mode other than ON_CLOSE)

Related to that, HibernateTransactionManager specifically checks for active physical connections on reset as of Hibernate 5.

Issue: SPR-13269
Issue: SPR-13002

spring-orm-hibernate5/src/main/java/org/springframework/orm/hibernate5/HibernateTransactionManager.java

@@ -641,7 +641,7 @@ public class HibernateTransactionManager extends AbstractPlatformTransactionMana
 		}
 
 		Session session = txObject.getSessionHolder().getSession();
-		if (this.prepareConnection && session.isConnected() && isSameConnectionForEntireSession(session)) {
+		if (this.prepareConnection && isPhysicallyConnected(session)) {
 			// We're running with connection release mode "on_close": We're able to reset
 			// the isolation level and/or read-only flag of the JDBC Connection here.
 			// Else, we need to rely on the connection pool to perform proper cleanup.
@@ -704,8 +704,27 @@ public class HibernateTransactionManager extends AbstractPlatformTransactionMana
 	 * @see ConnectionReleaseMode#ON_CLOSE
 	 */
 	protected boolean isSameConnectionForEntireSession(Session session) {
-		// TODO: The best we can do is to assume we're safe.
-		return true;
+		if (!(session instanceof SessionImplementor)) {
+			// The best we can do is to assume we're safe.
+			return true;
+		}
+		ConnectionReleaseMode releaseMode =
+				((SessionImplementor) session).getJdbcCoordinator().getConnectionReleaseMode();
+		return ConnectionReleaseMode.ON_CLOSE.equals(releaseMode);
+	}
+
+	/**
+	 * Determine whether the given Session is (still) physically connected
+	 * to the database, that is, holds an active JDBC Connection internally.
+	 * @param session the Hibernate Session to check
+	 * @see #isSameConnectionForEntireSession(Session)
+	 */
+	protected boolean isPhysicallyConnected(Session session) {
+		if (!(session instanceof SessionImplementor)) {
+			// The best we can do is to check whether we're logically connected.
+			return session.isConnected();
+		}
+		return ((SessionImplementor) session).getJdbcCoordinator().getLogicalConnection().isPhysicallyConnected();
 	}
 
 

spring-orm/src/main/java/org/springframework/orm/jpa/vendor/HibernateJpaDialect.java

@@ -22,6 +22,7 @@ import java.sql.SQLException;
 import javax.persistence.EntityManager;
 import javax.persistence.PersistenceException;
 
+import org.apache.commons.logging.LogFactory;
 import org.hibernate.FlushMode;
 import org.hibernate.HibernateException;
 import org.hibernate.NonUniqueObjectException;
@@ -146,13 +147,12 @@ public class HibernateJpaDialect extends DefaultJpaDialect {
 
 		boolean isolationLevelNeeded = (definition.getIsolationLevel() != TransactionDefinition.ISOLATION_DEFAULT);
 		Integer previousIsolationLevel = null;
-		boolean resetConnection = false;
+		Connection preparedCon = null;
 
 		if (isolationLevelNeeded || definition.isReadOnly()) {
 			if (this.prepareConnection) {
-				Connection con = HibernateConnectionHandle.doGetConnection(session);
-				previousIsolationLevel = DataSourceUtils.prepareConnectionForTransaction(con, definition);
-				resetConnection = true;
+				preparedCon = HibernateConnectionHandle.doGetConnection(session);
+				previousIsolationLevel = DataSourceUtils.prepareConnectionForTransaction(preparedCon, definition);
 			}
 			else if (isolationLevelNeeded) {
 				throw new InvalidIsolationLevelException(getClass().getSimpleName() +
@@ -167,7 +167,7 @@ public class HibernateJpaDialect extends DefaultJpaDialect {
 
 		// Adapt flush mode and store previous isolation level, if any.
 		FlushMode previousFlushMode = prepareFlushMode(session, definition.isReadOnly());
-		return new SessionTransactionData(session, previousFlushMode, resetConnection, previousIsolationLevel);
+		return new SessionTransactionData(session, previousFlushMode, preparedCon, previousIsolationLevel);
 	}
 
 	@Override
@@ -176,7 +176,7 @@ public class HibernateJpaDialect extends DefaultJpaDialect {
 
 		Session session = getSession(entityManager);
 		FlushMode previousFlushMode = prepareFlushMode(session, readOnly);
-		return new SessionTransactionData(session, previousFlushMode, false, null);
+		return new SessionTransactionData(session, previousFlushMode, null, null);
 	}
 
 	protected FlushMode prepareFlushMode(Session session, boolean readOnly) throws PersistenceException {
@@ -321,15 +321,15 @@ public class HibernateJpaDialect extends DefaultJpaDialect {
 
 		private final FlushMode previousFlushMode;
 
-		private final boolean resetConnection;
+		private final Connection preparedCon;
 
 		private final Integer previousIsolationLevel;
 
 		public SessionTransactionData(
-				Session session, FlushMode previousFlushMode, boolean resetConnection, Integer previousIsolationLevel) {
+				Session session, FlushMode previousFlushMode, Connection preparedCon, Integer previousIsolationLevel) {
 			this.session = session;
 			this.previousFlushMode = previousFlushMode;
-			this.resetConnection = resetConnection;
+			this.preparedCon = preparedCon;
 			this.previousIsolationLevel = previousIsolationLevel;
 		}
 
@@ -337,9 +337,15 @@ public class HibernateJpaDialect extends DefaultJpaDialect {
 			if (this.previousFlushMode != null) {
 				this.session.setFlushMode(this.previousFlushMode);
 			}
-			if (this.resetConnection && this.session.isConnected()) {
-				Connection con = HibernateConnectionHandle.doGetConnection(this.session);
-				DataSourceUtils.resetConnectionAfterTransaction(con, this.previousIsolationLevel);
+			if (this.preparedCon != null && this.session.isConnected()) {
+				Connection conToReset = HibernateConnectionHandle.doGetConnection(this.session);
+				if (conToReset != this.preparedCon) {
+					LogFactory.getLog(HibernateJpaDialect.class).warn(
+							"JDBC Connection to reset not identical to originally prepared Connection - please " +
+							"make sure to use connection release mode ON_CLOSE (the default) and to run against " +
+							"Hibernate 4.2+ (or switch HibernateJpaDialect's prepareConnection flag to false");
+				}
+				DataSourceUtils.resetConnectionAfterTransaction(conToReset, this.previousIsolationLevel);
 			}
 		}
 	}