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Use native JPA API

Use native JPA API

Since Spring 3.0, Spring embrace JPA quickly, and JPA is the first class citizen in Spring core framework. And in the latest Spring, JPA support is improved and the usage of JPA is more friendly than Hibernate.

Configuration

An example of XML format configuration is shown below:
<jdbc:embedded-database id="dataSource" >    
</jdbc:embedded-database>

<bean class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"
id="entityManagerFactory">
    <property name="persistenceUnitName" value="persistenceUnit" />
    <property name="dataSource" ref="dataSource" />
    <property name="persistenceProviderClass" value="org.hibernate.ejb.HibernatePersistence"></property>
    <property name="packagesToScan">
        <array>
            <value>com.hantsylabs.example.spring.model</value>
        </array>
    </property>
    <property name="jpaProperties">
        <value>
            hibernate.format_sql=true
            hibernate.show_sql=true
            hibernate.hbm2ddl.auto=create
        </value>
    </property>
</bean>

<bean class="org.springframework.orm.jpa.JpaTransactionManager"
        id="transactionManager">
    <property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>

<context:component-scan
 base-package="com.hantsylabs.example.spring.dao,com.hantsylabs.example.spring.jpa">
</context:component-scan>
Firstly, it declares a DataSource bean.
Then registers a EntityManagerFactoryBean bean, there are two version of EntityManagerFactoryBean are provided in Spring.
  • LocalEntityManagerFactoryBean reads the standard JPA configuration file from /META-INF/peresistence.xml in the project and prepare a JPA EntityManagerFactory at runtime.
  • LocalContainerEntityManagerFactoryBean is an advanced version and it provides more features. It is more friendly for container environment. It allow you specify the location of persistence.xml file. You can also configure a Spring loadTimeWeaver. Use this version, you can reuse the DataSource bean, and override the properties. In another word, you are free from maintaining the JPA specific configuration file( /META-INF/persistence.xml), you do not need it at all.
In this example, LocalContainerEntityManagerFactoryBean is used, and no JPA specific configuration file( /META-INF/persistence.xml) is placed in projects, the LocalContainerEntityManagerFactoryBean bean is responsible for building the JPA resources for you.
At last declare a JPA transaction manager.
The following is the Java configuration example, it is equivalent to the before XML format.
@Configuration
@ComponentScan(basePackages = { "com.hantsylabs.example.spring.dao",
        "com.hantsylabs.example.spring.jpa" })
public class JpaConfig {

    @Bean
    public DataSource dataSource() {
        return new EmbeddedDatabaseBuilder().build();
    }

    @Bean
    public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
        LocalContainerEntityManagerFactoryBean emf = new LocalContainerEntityManagerFactoryBean();
        emf.setDataSource(dataSource());
        emf.setPackagesToScan("com.hantsylabs.example.spring.model");
        emf.setPersistenceProvider(new HibernatePersistence());
        emf.setJpaProperties(jpaProperties());
        return emf;
    }

    private Properties jpaProperties() {
        Properties extraProperties = new Properties();
        extraProperties.put("hibernate.format_sql", "true");
        extraProperties.put("hibernate.show_sql", "true");
        extraProperties.put("hibernate.hbm2ddl.auto", "create");
        return extraProperties;
    }

    @Bean
    public PlatformTransactionManager transactionManager() {
        return new JpaTransactionManager(entityManagerFactory().getObject());
    }

}

Example codes

@Repository
public class JpaConferenceDaoImpl implements ConferenceDao {
    private static final Logger log = LoggerFactory
            .getLogger(JpaConferenceDaoImpl.class);

    @PersistenceContext
    private EntityManager entityManager;

    @Override
    public Conference findById(Long id) {
        return (Conference) entityManager.find(Conference.class, id);

    }
}
As you see, it uses @PersistenceContext to inject the JPA EntityManager bean, there is only one Spring specific @Repository annotation in the above codes.
If you are using JSR330, you can replace the @Repository with @Named, we will discuss this topic in further posts.
@Named
public class JpaConferenceDaoImpl implements ConferenceDao {

    @PersistenceContext
    private EntityManager entityManager;

}
Now, the above codes are no difference between Spring and Java EE, it can be run in Spring(especially a Servlet container, such as Apache Tomcat, Jetty) and any standard Java EE 6 container(for example JBoss AS 7, Glassfish 3.1). Of course you have to contribute extra effort on the base configuration for different platform.

Check out the codes from my github.com,  https://github.com/hantsy/spring-sandbox.
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