Propagate read-only status through setDefaultReadOnly(true) for JPA

This involves a new ResourceTransactionDefinition variant that JpaTransactionManager indicates a transaction-local EntityManager on. HibernateJpaDialect uses this indicator for hard read-only behavior.

Issue: SPR-16956

spring-tx/src/main/java/org/springframework/transaction/support/ResourceTransactionDefinition.java

@@ -0,0 +1,39 @@
+/*
+ * Copyright 2002-2018 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.transaction.support;
+
+import org.springframework.transaction.TransactionDefinition;
+
+/**
+ * Extended variant of {@link TransactionDefinition}, indicating a resource transaction
+ * and in particular whether the transactional resource is ready for local optimizations.
+ *
+ * @author Juergen Hoeller
+ * @since 5.1
+ * @see ResourceTransactionManager
+ */
+public interface ResourceTransactionDefinition extends TransactionDefinition {
+
+	/**
+	 * Determine whether the transactional resource is ready for local optimizations.
+	 * @return {@code true} if the resource is known to be entirely transaction-local,
+	 * not affecting any operations outside of the scope of the current transaction
+	 * @see #isReadOnly()
+	 */
+	boolean isLocalResource();
+
+}