How to inject JPA EntityManager using spring

Question

Hello all!
I have a few questions about jpa + spring integration running on tomcat, i've been looking fo some time and couldn't find any concrete answer, so here it goes:

Is it possible to have spring to inject the JPA entityManager object into my DAO class without extending JpaDaoSupport? if yes, does spring manage the transaction in this case?

I'm trying to keep spring configuration as simple as possible:

<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
    <property name="entityManagerFactory" ref="em"/>
</bean>
 <bean id="em" class="org.springframework.orm.jpa.LocalEntityManagerFactoryBean">
    <property name="persistenceUnitName" value="myPU"/>
</bean>

EDIT: that was very helpfull, thank you all!

Answer 1

I think this is exactly what you are looking for.

Answer 2

Yes, although it's full of gotchas, since JPA is a bit peculiar. It's very much worth reading the documentation on injecting JPA EntityManager and EntityManagerFactory, without explicit Spring dependencies in your code:

http://static.springsource.org/spring/docs/3.0.x/reference/html/orm.html#orm-jpa-straight

This allows you to either inject the EntityManagerFactory, or else inject a thread-safe, transactional proxy of an EntityManager directly. The latter makes for simpler code, but means more Spring plumbing is required.

Answer 3

Is it possible to have spring to inject the JPA entityManager object into my DAO class whitout extending JpaDaoSupport? if yes, does spring manage the transaction in this case?

This is documented black on white in 12.6.3. Implementing DAOs based on plain JPA:

It is possible to write code against the plain JPA without using any Spring dependencies, using an injected EntityManagerFactory or EntityManager. Note that Spring can understand @PersistenceUnit and @PersistenceContext annotations both at field and method level if a PersistenceAnnotationBeanPostProcessor is enabled. A corresponding DAO implementation might look like this (...)

And regarding transaction management, have a look at 12.7. Transaction Management:

Spring JPA allows a configured JpaTransactionManager to expose a JPA transaction to JDBC access code that accesses the same JDBC DataSource, provided that the registered JpaDialect supports retrieval of the underlying JDBC Connection. Out of the box, Spring provides dialects for the Toplink, Hibernate and OpenJPA JPA implementations. See the next section for details on the JpaDialect mechanism.