Align JpaTransactionManager default for nestedTransactionAllowed flag

Closes gh-35457

Author: jhoeller

spring-orm/src/main/java/org/springframework/orm/jpa/JpaTransactionManager.java

@@ -93,11 +93,11 @@
  *
  * <p>This transaction manager supports nested transactions via JDBC Savepoints.
  * The {@link #setNestedTransactionAllowed "nestedTransactionAllowed"} flag defaults
- * to {@code false} though, since nested transactions will just apply to the JDBC
- * Connection, not to the JPA EntityManager and its cached entity objects and related
- * context. You can manually set the flag to {@code true} if you want to use nested
- * transactions for JDBC access code which participates in JPA transactions (provided
- * that your JDBC driver supports Savepoints). <i>Note that JPA itself does not support
+ * to "false", though, as nested transactions will just apply to the JDBC Connection,
+ * not to the JPA EntityManager and its cached entity objects and related context.
+ * You can manually set the flag to "true" if you want to use nested transactions
+ * for JDBC access code which participates in JPA transactions (provided that your
+ * JDBC driver supports savepoints). <i>Note that JPA itself does not support
  * nested transactions! Hence, do not expect JPA access code to semantically
  * participate in a nested transaction.</i>
  *
@@ -136,15 +136,13 @@ public class JpaTransactionManager extends AbstractPlatformTransactionManager
 	 * @see #setEntityManagerFactory
 	 */
 	public JpaTransactionManager() {
-		setNestedTransactionAllowed(true);
 	}
 
 	/**
 	 * Create a new JpaTransactionManager instance.
 	 * @param emf the EntityManagerFactory to manage transactions for
 	 */
 	public JpaTransactionManager(EntityManagerFactory emf) {
-		this();
 		this.entityManagerFactory = emf;
 		afterPropertiesSet();
 	}

spring-orm/src/main/java/org/springframework/orm/jpa/hibernate/HibernateTransactionManager.java

@@ -88,12 +88,12 @@
  * such a scenario (see container setup).
  *
  * <p>This transaction manager supports nested transactions via JDBC Savepoints.
- * The {@link #setNestedTransactionAllowed} "nestedTransactionAllowed"} flag defaults
+ * The {@link #setNestedTransactionAllowed "nestedTransactionAllowed"} flag defaults
  * to "false", though, as nested transactions will just apply to the JDBC Connection,
  * not to the Hibernate Session and its cached entity objects and related context.
  * You can manually set the flag to "true" if you want to use nested transactions
  * for JDBC access code which participates in Hibernate transactions (provided that
- * your JDBC driver supports Savepoints). <i>Note that Hibernate itself does not
+ * your JDBC driver supports savepoints). <i>Note that Hibernate itself does not
  * support nested transactions! Hence, do not expect Hibernate access code to
  * semantically participate in a nested transaction.</i>
  *