Tips for Managing Sustainability Context Manually

Question

I am studying using JPA for my data access code. I am trying to write a business layer and data access layer so that it works in a web application and Java SE application. Therefore, I cannot use the container persistence context. Most of my JPA services show examples in a container-managed environment.

Currently, I get an EntityManagerFactory every time I create a new instance of the service class. For each operation (for example, add, get, etc.) I open the EntityManager, start the transaction, perform the operations, commit and close the EntityManager and EntityManagerFactory. I would like you to have problems maintaining context outside the Java EE environment.

Are there any recommendations when you are not using a container driven context? Are there any independent Java EE persistence context managers? Are there any recommended patterns?

Thank,

Al

Update

Thank you eveyone for the info. Everything was very helpful.

Answer 1

I'm not sure about the best practices related to this, but I spent a lot of time doing something like this work.

Basically you need to build something EntityManagerwith. I have always used Spring for this. Their documentation documentation ):

<bean id="myEmf" class="org.springframework.orm.jpa.LocalEntityManagerFactoryBean">
  <property name="persistenceUnitName" value="myPersistenceUnit"/>
</bean>

, , , , , . , , - .

hibernate (persistence.xml META-INF/):

<property name="hibernate.connection.driver_class" value="com.company.driver" />
<property name="hibernate.connection.url" value="some:jdbc@string" />
<property name="hibernate.connection.username" value="myuser" />
<property name="hibernate.connection.password" value="mypassword" />

, Spring, EntityManagerFactory (.. context.getBean("myEmf")).

LocalContainerEntityManagerFactoryBean , . , , , , Hibernate. persistence.xml, (, , , oracle 10g):

<bean id="emf" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="dataSource" ref="myDatasource" />
    <property name="persistenceProvider">
        <bean class="org.hibernate.ejb.HibernatePersistence" />
    </property>
</bean>

Spring BasicDataSource Apache dbcp, .

, JPA . , , Hibernate JPA, , , JPA. , API- Hibernate.

Answer 2

EntityManagerFactory , . (, add, get ..) EntityManager, , , EntityManager EntityManagerFactory.

EntityManagerFactory . EntityManagerFactory . , , , :

public class JpaUtil {
    private JpaUtil() {}

    private static EntityManagerFactory emf = null;

    static {
        try {
            emf = Persistence.createEntityManagerFactory("MyPu");
        } catch (Throwable ex) {
            throw new ExceptionInInitializerError(ex);
        }
    }

    public static EntityManager getEntityManager() {
        return emf.createEntityManager();
    }
}

( ThreadLocal, . ), EntityManager .

, Java EE.

- , Spring EntityManager Spring beans, Java SE.

JPA Spring Spring , , :

• LocalEntityManagerFactoryBean, EntityManagerFactory
• JpaTransactionManager JPA
• <tx:annotation-driven />, Spring @Transactional
• bean!

Spring, .

• Spring
  • 13. (ORM)
  • 13.5 "JPA"

.

• JPA Spring Spring
• Spring HibernateTemplate / JpaTemplate?

Answer 3

JPA Java EE. :

• Hibernate
• EclipseLink

Java EE.

, Java EE "open a EntityManager, , EntityManager, PITA .

EE, JPA Spring. . , JpaDaoSupport Transactional .

EE:

    import java.util.List;
    import org.springframework.orm.jpa.support.JpaDaoSupport;

    public class SpeakerDAOImpl extends JpaDaoSupport implements SpeakerDAO {

    public Speaker findSpeaker(long id) {
       return getJpaTemplate().find(Speaker.class,id);
    }

    @Transactional
    public void saveSpeaker(Speaker s) {
       getJpaTemplate().persist(s);
    }
  }

, ..:

• http://www.jroller.com/javajpa/entry/creating_a_generic_dao_using
• EntityManagerFactory + jpadaosupport
• http://icoloma.blogspot.com/2006/11/jpa-and-spring-fucking-cooltm_26.html
• http://www.gbcacm.org/sites/www.gbcacm.org/files/slides/4%20-%20Spring-JPA-Hibernate.pdf ( )

Answer 4

, Ebean ORM JPA- (@Entity ..), " " "- , EntityManager.

Ebean API JPA ( "" API - EntityManager, / beans ..), EntityManager, .