anchor.diff:  `PersistenceUnitManager` is specified, one is created and used internally by
   `LocalContainerEntityManagerFactoryBean`.
   
  +[[orm-jpa-setup-background]]
  +===== Background bootstrapping
  +
  +`LocalContainerEntityManagerFactoryBean` supports background bootstrapping through
  +the `bootstrapExecutor` property:
  +
  +[source,xml,indent=0]
  +[subs="verbatim,quotes"]
  +----
  +	<bean id="emf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
  +		<property name="bootstrapExecutor">
  +			<bean class="org.springframework.core.task.SimpleAsyncTaskExecutor"/>
  +		</property>
  +	</bean>
  +----
  +
  +The actual JPA provider bootstrapping will be handed off to the specified executor then,
  +running in parallel to the application bootstrap thread. The exposed `EntityManagerFactory`
  +proxy can be injected into other application components and is even able to respond
  +`EntityManagerFactoryInfo` configuration inspection. However, once the actual JPA provider
  +is being accessed by other components, e.g. calling `createEntityManager`, those calls
  +will block until the background bootstrapping has completed. In particular, when using
  +Spring Data JPA, make sure to set up deferred bootstrapping for its repositories as well.
  +
   
   [[orm-jpa-dao]]
   ==== Implementing DAOs based on JPA: EntityManagerFactory and EntityManager
  
positive.code: ====
  
  You can also use Hibernate local transactions easily, as shown in the following
  examples. In this case, you need to define a Hibernate `LocalSessionFactoryBean`, which
  your application code will use to obtain Hibernate `Session` instances.
  
  The `DataSource` bean definition will be similar to the local JDBC example shown
  previously and thus is not shown in the following example.
  
negative.code: ====
  As of Spring Framework 5.0, Spring requires Hibernate ORM 4.3 or later for JPA support
  and even Hibernate ORM 5.0+ for programming against the native Hibernate Session API.
  Note that the Hibernate team does not maintain any versions prior to 5.1 anymore and
  is likely to focus on 5.3+ exclusively soon.
  ====
  
  
  