TransactionAwareDataSourceProxy locally handles get/clearWarnings call

Closes gh-23346

Author: jhoeller

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2019 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -124,7 +124,7 @@ public Connection getConnection() throws SQLException {
 	/**
 	 * Wraps the given Connection with a proxy that delegates every method call to it
 	 * but delegates {@code close()} calls to DataSourceUtils.
-	 * @param targetDataSource DataSource that the Connection came from
+	 * @param targetDataSource the DataSource that the Connection came from
 	 * @return the wrapped Connection
 	 * @see java.sql.Connection#close()
 	 * @see DataSourceUtils#doReleaseConnection
@@ -203,6 +203,10 @@ else if (method.getName().equals("isWrapperFor")) {
 					return true;
 				}
 			}
+			else if (method.getName().equals("getWarnings") || method.getName().equals("clearWarnings")) {
+				// Avoid creation of target Connection on pre-close cleanup (e.g. in Hibernate Session)
+				return null;
+			}
 			else if (method.getName().equals("close")) {
 				// Handle close method: only close if not within a transaction.
 				DataSourceUtils.doReleaseConnection(this.target, this.targetDataSource);