Configuration to be able to @Inject EntityManager in Seam 3

问题

In my project I use Seam 3 and I am having issues injecting the EntityManager with the @Inject annotation. I am pretty sure there is some kind of configuration to make sure the EnityManager knows which PersistenceUnit to use. For example with EJB you can type:

@PersistenceContext(unitName="MY_PERSISTENCE_UNIT_NAME")
private EntityManager eManager;

which persistence unit is configured in the persistence.xml file. Here is my pseudo configuration:

<?xml version="1.0" encoding="UTF-8"?>
<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="MY_PERSISTENCE_UNIT_NAME" transaction-type="JTA">

        <provider>org.hibernate.ejb.HibernatePersistence</provider>
        <jta-data-source>java:jboss/TimeReportDS</jta-data-source>
        <mapping-file>META-INF/orm.xml</mapping-file> 

        <class>....</class>
        <class>....</class>
        <class>....</class>

        <properties>

            <property name="jboss.entity.manager.factory.jndi.name"
                value="java:/modelEntityManagerFactory" />

            <!-- PostgreSQL Configuration File -->
            <property name="hibernate.connection.driver_class" value="org.postgresql.Driver" />
            <property name="hibernate.connection.password" value="password" />
            <property name="hibernate.connection.url" value="jdbc:postgresql://192.168.2.125:5432/t_report" />
            <property name="hibernate.connection.username" value="username" />

            <!-- Specifying DB Driver, providing hibernate cfg lookup
                 and providing transaction manager configuration -->
            <property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect" />
            <property name="hibernate.transaction.factory_class" value="org.hibernate.transaction.JTATransactionFactory"/>
            <property name="hibernate.transaction.manager_lookup_class"
                value="org.hibernate.transaction.JBossTransactionManagerLookup" />
            <property name="hibernate.archive.autodetection" value="class" />

            <!-- Useful configuration during development - developer can see structured SQL queries -->
            <property name="hibernate.show_sql" value="true" />
            <property name="hibernate.format_sql" value="false" />

        </properties>
    </persistence-unit>
</persistence>  

I have read some articles about Seam 2 but there the configuration is made in components.xml file by adding the:

<persistence:managed-persistence-context
        name="entityManager" auto-create="true" persistence-unit-jndi-name="java:/modelEntityManagerFactory" />

inside the <components> tag. The next step in Seam 2 is to add the:

<property name="jboss.entity.manager.factory.jndi.name"
                value="java:/modelEntityManagerFactory" />

in the persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence ...>
    <persistence-unit name="MY_PERSISTENCE_UNIT_NAME" ...>
        ...
        <properties>
            ...

            <property name="jboss.entity.manager.factory.jndi.name"
                value="java:/modelEntityManagerFactory" />

        </properties>
    </persistence-unit>
</persistence>

but it seam that in Seam 3 there is no file components.xml. Also there is no attribute unitName in @Inject annotation to specify the persistence unit.

So please help me to configure my project so I can use the @Inject with EntityManager as shown in many examples on the net.

I use Postgres database and JBoss AS 7.

EDIT: Adding an example. I don't use the EntityManager in an Entity class.

@Named("validateReportAction")
@SessionScoped
public class ValidateReportAction extends ReportAction implements Serializable {

    private static final long serialVersionUID = -2456544897212149335L;

    @Inject
    private EntityManager em;
...
}  

Here in this @Inject I get warning from Eclipse "No bean is eligible for injection to the injection point [JSR-299 §5.2.1]"

If I use the @Inject on some beans that are marked as Entity the @Inject works fine.

回答1:

You can use @PersistenceContext on a CDI bean. It doesn't have to be an EJB.

If for some reason you want to use @Inject, you have to do more work. @Inject doesn't know about the EntityManager; it can only inject other managed beans. Happily, there is a simple workaround - use a producer method that acts as a simple trampoline.

@ApplicationScoped
public class EntityManagerProducer {

    @PersistenceContext
    private EntityManager entityManager;

    @Produces
    @RequestScoped
    public EntityManager getEntityManager {
        return entityManager;
    }

    public void closeEntityManager(@Disposes EntityManager em) {
        if (em != null && em.getTransaction().isActive()) {
            em.getTransaction().rollback();
        }
        if (em != null && em.isOpen()) {
            em.close();
        }
    }

}

You can now use @Inject to inject the EntityManager. The injected EntityManager will be RequestScoped, while the EntityManagerProducer is ApplicationScoped. Furthermore, the entityManager must be closed.

来源：https://stackoverflow.com/questions/8763115/configuration-to-be-able-to-inject-entitymanager-in-seam-3