Simplify connection handling setup and add a note about quarkusio#7242

DELAYED_ACQUISITION_AND_RELEASE_AFTER_STATEMENT, on top of being less
efficient, also leads to resource leaks (that are caught by Agroal,
but still).

Signed-off-by: Yoann Rodière <yoann@hibernate.org>

extensions/hibernate-orm/runtime/src/main/java/io/quarkus/hibernate/orm/runtime/boot/FastBootMetadataBuilder.java

@@ -242,20 +242,18 @@ private MergedSettings mergeSettings(PersistenceUnitDescriptor persistenceUnit)
         //Agroal already does disable auto-commit, so Hibernate ORM should trust that:
         cfg.put(AvailableSettings.CONNECTION_PROVIDER_DISABLES_AUTOCOMMIT, Boolean.TRUE.toString());
 
-        /**
+        /*
          * Set CONNECTION_HANDLING to DELAYED_ACQUISITION_AND_RELEASE_BEFORE_TRANSACTION_COMPLETION
          * as it generally performs better, at no known drawbacks.
          * This is a new mode in Hibernate ORM, it might become the default in the future.
          *
+         * Note: other connection handling modes lead to leaked resources, statements in particular.
+         * See https://github.com/quarkusio/quarkus/issues/7242, https://github.com/quarkusio/quarkus/issues/13273
+         *
          * @see org.hibernate.resource.jdbc.spi.PhysicalConnectionHandlingMode
          */
-        {
-            final Object explicitSetting = cfg.get(AvailableSettings.CONNECTION_HANDLING);
-            if (explicitSetting == null) {
-                cfg.put(AvailableSettings.CONNECTION_HANDLING,
-                        PhysicalConnectionHandlingMode.DELAYED_ACQUISITION_AND_RELEASE_BEFORE_TRANSACTION_COMPLETION);
-            }
-        }
+        cfg.putIfAbsent(AvailableSettings.CONNECTION_HANDLING,
+                PhysicalConnectionHandlingMode.DELAYED_ACQUISITION_AND_RELEASE_BEFORE_TRANSACTION_COMPLETION);
 
         if (readBooleanConfigurationValue(cfg, WRAP_RESULT_SETS)) {
             LOG.warn("Wrapping result sets is not supported. Setting " + WRAP_RESULT_SETS + " to false.");