Spring #PersistenceContext how to inject manually the entity manager in my GenericDao - spring

Question

Hallo all:
I read the spring reference about this point.
I would choose to use the #PersistenceContext in my DAO to inject a shared transactional entity manager, but since I use the GenericDaoJpaImpl pattern over two entityManagerFactories that point to 2 different persistence units I cannot use it.
So right now in my application I have this configuration:
entityManagerFactoryies:
<bean id="entityManagerFactoryIban0" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="persistenceXmlLocation" value="classpath:META-INF/contratto-persistence-iban0.xml" />
</bean>
<bean id="entityManagerFactoryCont0" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="persistenceXmlLocation" value="classpath:META-INF/contratto-persistence-cont0.xml" />
</bean>
<bean abstract="true" id="abstractDaoJpaImplIban0" lazy-init="false">
<property name="entityManagerFactory" ref="entityManagerFactoryIban0" />
</bean>
<bean abstract="true" id="abstractDaoJpaImplCont0" lazy-init="false">
<property name="entityManagerFactory" ref="entityManagerFactoryCont0" />
</bean>
Then each of my DAOs is an instance of the GenericDaoImpl:
#Repository
public class GenericDaoJpaImpl<T, ID extends Serializable> implements GenericDao<T, ID> {
private Class<T> entityClass;
private EntityManagerFactory entityManagerFactory;
public void setEntityManagerFactory(EntityManagerFactory entityManagerFactory) {
this.entityManagerFactory = entityManagerFactory;
}
public GenericDaoJpaImpl() {
super();
}
public GenericDaoJpaImpl(Class<T> entityClass) {
super();
this.entityClass = entityClass;
}
/**
* #see it.alten.intesasanpaolo.contratto.dao.common.GenericDao#getItemByID(java.io.Serializable)
*/
#Override
public T getItemByID(ID id) {
EntityManager em = entityManagerFactory.createEntityManager();
return em.find(entityClass, id);
}
I construct my dao via spring in this way:
<bean id="eventMessageDao" parent="abstractDaoJpaImplCont0" class="it.alten.intesasanpaolo.contratto.dao.common.GenericDaoJpaImpl">
<constructor-arg>
<value>it.alten.intesasanpaolo.contratto.domain.event.OnlineEventMessage</value>
</constructor-arg>
</bean>
Now I would like to modify the GenericDaoJpaImpl as described in the spring documentation not to be associated to the entityManagerFactory from which I have to create every time the entityManager but directly to the entityManager.
I would like to define it in the context in a way I can inject it to the correct abstract dao to be extended from every dao.
<bean abstract="true" id="abstractDaoJpaImplIban0" lazy-init="false">
<property name="entityManagerFactory" ref="entityManagerFactoryIban0" />
</bean>
How can I achieve this?
kind regards
Massimo

Answer 1

You can use SharedEntityManagerBean to construct a transactional EntityManager from the EntityManagerFactory:
<bean id="entityManagerFactoryIban0"
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
...
</bean>
<bean id="entityManagerIban0"
class="org.springframework.orm.jpa.support.SharedEntityManagerBean">
<property name="entityManagerFactory" ref="entityManagerFactoryIban0" />
</bean>
<bean abstract="true" id="abstractDaoJpaImplIban0" lazy-init="false">
<property name="entityManager" ref="entityManagerIban0" />
</bean>

Answer 2

You can provide the persistence unit name in the xml configuration, using the SharedEntityManagerBean, like below:
<bean id="testDao" class="com.test.persistence.dao.BaseDAO">
<property name="entityManager">
<bean class="org.springframework.orm.jpa.support.SharedEntityManagerBean">
<property name="persistenceUnitName" value="persistence-test-unit" />
</bean>
</property>
</bean>
of course, you can have the SharedEntityManagerBean as a separate bean
Here, I m injecting entityManager into BaseDAO as you're doing using #PersistenceContext(unitName="...")