Injecting one of the two @PersistenceContext

Question

Consider having two entity manager factories:

<bean id="writeEntityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">...</bean>
<bean id="readOnlyEntityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">...</bean>

Then I want to have two Beans to which I would inject the correct persistence context:

<bean id="readOnlyManager" class="..MyDatabaseManager">
<bean id="writeManager" class="..MyDatabaseManager">

The bean would look something like:

public class MyDatabaseManager {

    private javax.persistence.EntityManager em;

    public EntityManager(javax.persistence.EntityManager em) {
        this.em = em;
    }
    ...
}

This obviously doesn't work, because EntityManager is not a bean and cannot be injected in this way:

No qualifying bean of type 'javax.persistence.EntityManager' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {}

How can I qualify correct EntityManager in the bean? I used to use @PersistenceContext annotation, but this is not usable as I need to inject it.

How can I specify the PersistenceContext for such Bean?

UPDATE: My question is how to inject PersistenceContext with qualifier via XML, not via annotation.

Answer 1

persistence.xml (2 persistence unit for 2 different entitymanager, based on your persistence provider here i ma using HibernatePersistence)

<persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
   <persistence-unit name="pu1">
      <provider>org.hibernate.ejb.HibernatePersistence</provider>
   </persistence-unit>

   <persistence-unit name="pu2">
      <provider>org.hibernate.ejb.HibernatePersistence</provider>
   </persistence-unit>   
</persistence>

Make sure you are assigning the persistence-unit to entity manager using property persistenceUnitName

    <bean id="writeEntityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
            <property name="persistenceXmlLocation" value="classpath: of yout persistence xml" />
            <property name="persistenceUnitName" value="pu1" />  
             .....other configuration of em..  
    </bean>

same for other em.

Now, use constructor injection for MyDatabaseManager to inject EntityManager (using qualifier name ex. writeEntityManagerFactory )

<bean id="mdm" class="MyDatabaseManager">
     <constructor-arg ref = "writeEntityManagerFactory"/>
</bean>