DataSourceTransactionManager resets ConnectionHolder on doBegin failure

Issue: SPR-12280

spring-jdbc/src/main/java/org/springframework/jdbc/datasource/DataSourceTransactionManager.java

@@ -179,7 +179,7 @@ public class DataSourceTransactionManager extends AbstractPlatformTransactionMan
 		DataSourceTransactionObject txObject = new DataSourceTransactionObject();
 		txObject.setSavepointAllowed(isNestedTransactionAllowed());
 		ConnectionHolder conHolder =
-			(ConnectionHolder) TransactionSynchronizationManager.getResource(this.dataSource);
+				(ConnectionHolder) TransactionSynchronizationManager.getResource(this.dataSource);
 		txObject.setConnectionHolder(conHolder, false);
 		return txObject;
 	}
@@ -238,7 +238,10 @@ public class DataSourceTransactionManager extends AbstractPlatformTransactionMan
 		}
 
 		catch (Throwable ex) {
-			DataSourceUtils.releaseConnection(con, this.dataSource);
+			if (txObject.isNewConnectionHolder()) {
+				DataSourceUtils.releaseConnection(con, this.dataSource);
+				txObject.setConnectionHolder(null, false);
+			}
 			throw new CannotCreateTransactionException("Could not open JDBC Connection for transaction", ex);
 		}
 	}