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Document EntityManager injection via constructors/@Autowired 

Closes gh-15076
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Juergen Hoeller 2023-07-18 22:01:57 +02:00
parent 1ac0549881
commit 038dda97f8
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framework-docs/modules/ROOT/pages/data-access/orm/jpa.adoc
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@ -88,12 +88,6 @@ You can use this option for full JPA capabilities in a Spring-based application
This includes web containers such as Tomcat, stand-alone applications, and
integration tests with sophisticated persistence requirements.
NOTE: If you want to specifically configure a Hibernate setup, an immediate alternative
is to set up a native Hibernate `LocalSessionFactoryBean` instead of a plain JPA
`LocalContainerEntityManagerFactoryBean`, letting it interact with JPA access code
as well as native Hibernate access code.
See xref:data-access/orm/jpa.adoc#orm-jpa-hibernate[Native Hibernate setup for JPA interaction] for details.
The `LocalContainerEntityManagerFactoryBean` gives full control over
`EntityManagerFactory` configuration and is appropriate for environments where
fine-grained customization is required. The `LocalContainerEntityManagerFactoryBean`
@ -187,6 +181,7 @@ and automatic propagation of the weaver to all weaver-aware beans:
[source,xml,indent=0,subs="verbatim,quotes"]
----
<context:load-time-weaver/>
<bean id="emf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
...
</bean>
@ -425,20 +420,20 @@ Kotlin::
----
======
The `@PersistenceContext` annotation has an optional attribute called `type`, which defaults to
`PersistenceContextType.TRANSACTION`. You can use this default to receive a shared
The `@PersistenceContext` annotation has an optional attribute called `type`, which defaults
to `PersistenceContextType.TRANSACTION`. You can use this default to receive a shared
`EntityManager` proxy. The alternative, `PersistenceContextType.EXTENDED`, is a completely
different affair. This results in a so-called extended `EntityManager`, which is not
thread-safe and, hence, must not be used in a concurrently accessed component, such as a
Spring-managed singleton bean. Extended `EntityManager` instances are only supposed to be used#
Spring-managed singleton bean. Extended `EntityManager` instances are only supposed to be used
in stateful components that, for example, reside in a session, with the lifecycle of the
`EntityManager` not tied to a current transaction but rather being completely up to the
application.
.Method- and field-level Injection
****
You can apply annotations that indicate dependency injections (such as `@PersistenceUnit` and
`@PersistenceContext`) on field or methods inside a class -- hence the expressions
You can apply annotations that indicate dependency injections (such as `@PersistenceUnit`
and `@PersistenceContext`) on field or methods inside a class -- hence the expressions
"`method-level injection`" and "`field-level injection`". Field-level annotations are
concise and easier to use while method-level annotations allow for further processing of the
injected dependency. In both cases, the member visibility (public, protected, or private)
@ -460,12 +455,53 @@ No import of any Spring class is required. Moreover, as the JPA annotations are
the injections are applied automatically by the Spring container. This is appealing from
a non-invasiveness perspective and can feel more natural to JPA developers.
[[orm-jpa-dao-autowired]]
=== Implementing DAOs Based on `@Autowired` (typically with constructor-based injection)
`@PersistenceUnit` and `@PersistenceContext` can only be declared on methods and fields.
What about providing JPA resources via constructors and other `@Autowired` injection points?
`EntityManagerFactory` can easily be injected via constructors and `@Autowired` fields/methods
as long as the target is defined as a bean, e.g. via `LocalContainerEntityManagerFactoryBean`.
The injection point matches the original `EntityManagerFactory` definition by type as-is.
However, an `@PersistenceContext`-style shared `EntityManager` reference is not available for
regular dependency injection out of the box. In order to make it available for type-based
matching as required by `@Autowired`, consider defining a `SharedEntityManagerBean` as a
companion for your `EntityManagerFactory` definition:
[source,xml,indent=0,subs="verbatim,quotes"]
----
<bean id="emf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
...
</bean>
<bean id="em" class="org.springframework.orm.jpa.support.SharedEntityManagerBean">
<property name="entityManagerFactory" ref="emf"/>
</bean>
----
Alternatively, you may define an `@Bean` method based on `SharedEntityManagerCreator`:
[source,java,indent=0,subs="verbatim,quotes"]
----
@Bean("em")
public static EntityManager sharedEntityManager(EntityManagerFactory emf) {
return SharedEntityManagerCreator.createSharedEntityManager(emf);
}
----
In case of multiple persistence units, each `EntityManagerFactory` definition needs to be
accompanied by a corresponding `EntityManager` bean definition, ideally with qualifiers
that match with the distinct `EntityManagerFactory` definition in order to distinguish
the persistence units via `@Autowired @Qualifier("...")`.
[[orm-jpa-tx]]
== Spring-driven JPA transactions
== Spring-driven JPA Transactions
NOTE: We strongly encourage you to read xref:data-access/transaction/declarative.adoc[Declarative Transaction Management], if you have not
already done so, to get more detailed coverage of Spring's declarative transaction support.
NOTE: We strongly encourage you to read xref:data-access/transaction/declarative.adoc[Declarative Transaction Management],
if you have not already done so, to get more detailed coverage of Spring's declarative transaction support.
The recommended strategy for JPA is local transactions through JPA's native transaction
support. Spring's `JpaTransactionManager` provides many capabilities known from local
@ -478,11 +514,6 @@ to JDBC access code that accesses the same `DataSource`, provided that the regis
Spring provides dialects for the EclipseLink and Hibernate JPA implementations.
See the xref:data-access/orm/jpa.adoc#orm-jpa-dialect[next section] for details on the `JpaDialect` mechanism.
NOTE: As an immediate alternative, Spring's native `HibernateTransactionManager` is capable
of interacting with JPA access code, adapting to several Hibernate specifics and providing
JDBC interaction. This makes particular sense in combination with `LocalSessionFactoryBean`
setup. See xref:data-access/orm/jpa.adoc#orm-jpa-hibernate[Native Hibernate Setup for JPA Interaction] for details.
[[orm-jpa-dialect]]
== Understanding `JpaDialect` and `JpaVendorAdapter`