!!!Key / Id Property ermitteln
{{{
Session session = (Session)entityManager.getDelegate();
ClassMetadata metadata = session.getSessionFactory().getClassMetadata(type);
String keyName = metadata.getIdentifierPropertyName();
Class<?> keyType = metadata.getIdentifierType().getReturnedClass();
}}}

!!!Spring JPA
applicationContext.xml:
{{{
	<context:component-scan base-package="com.intersult"/>
	<aop:config proxy-target-class="true"/>
	<aop:aspectj-autoproxy/>
	
	<bean id="dataSource" class="${dataSource.class}" destroy-method="close">
		<property name="URL" value="${dataSource.url}"/>
		<property name="user" value="${dataSource.username}"/>
		<property name="password" value="${dataSource.password}"/>
	</bean>
	
	<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
		<property name="dataSource" ref="dataSource"/>
		<property name="loadTimeWeaver">
			<bean class="org.springframework.instrument.classloading.InstrumentationLoadTimeWeaver"/>
		</property>
	</bean>

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

	<tx:annotation-driven/>
}}}

!!!Spring Open EntityManager once in View Pattern
web.xml:
{{{
	<filter>
		<filter-name>EntityManagerFilter</filter-name>
		<filter-class>org.springframework.orm.jpa.support.OpenEntityManagerInViewFilter</filter-class>
	</filter>
	<filter-mapping>
		<filter-name>EntityManagerFilter</filter-name>
		<servlet-name>Faces Servlet</servlet-name>
	</filter-mapping>
}}}

!!!Spring Open EntityManager in Session
Nicht getestet ob das praktikabel ist.
{{{
public class OpenEntityManagerInSessionFilter extends OncePerRequestFilter {
	public static final String ENTITY_MANAGER_FACTORY_NAME = "entityManagerFactory";
	public static final String ENTITY_MANAGER_NAME = "entityManager";

	private String entityManagerFactoryBeanName = ENTITY_MANAGER_FACTORY_NAME;

	public void setEntityManagerFactoryBeanName(String entityManagerFactoryBeanName) {
		this.entityManagerFactoryBeanName = entityManagerFactoryBeanName;
	}

	public String getEntityManagerFactoryBeanName() {
		return entityManagerFactoryBeanName;
	}

	@Override
	protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain)
			throws ServletException, IOException {
		EntityManagerFactory entityManagerFactory = lookupEntityManagerFactory();
		boolean participate = false;
		try {
			if (TransactionSynchronizationManager.hasResource(entityManagerFactory)) {
				participate = true;
			} else {
				EntityManager entityManager = (EntityManager)request.getSession().getAttribute(ENTITY_MANAGER_NAME);
				if (entityManager == null) {
					entityManager = entityManagerFactory.createEntityManager();
					request.getSession().setAttribute(ENTITY_MANAGER_NAME, entityManager);
				}
				TransactionSynchronizationManager.bindResource(
					entityManagerFactory, new EntityManagerHolder(entityManager));
			}
			filterChain.doFilter(request, response);
		} finally {
			if (!participate)
				TransactionSynchronizationManager.unbindResource(entityManagerFactory);
		}
	}

	protected EntityManagerFactory lookupEntityManagerFactory() {
		WebApplicationContext wac = WebApplicationContextUtils.getRequiredWebApplicationContext(getServletContext());
		return (EntityManagerFactory) wac.getBean(getEntityManagerFactoryBeanName(), EntityManagerFactory.class);
	}
}
}}}

!!!Criteria Query
In Hibernate sind die Criteria Querys eine der mächstigsten Instrumente, da sie rein durch ein Programm erzeugt werden können.

{{{
	Criteria criteria = ((Session)entityManager.getDelegate()).createCriteria(Rule.class);
	ProjectionList projections = Projections.projectionList();
	projections.add(Projections.alias(Projections.groupProperty(selector.property()), "goal"));
	projections.add(Projections.alias(Projections.rowCount(), "count"));
	criteria.setProjection(projections);
	criteria.add(Restrictions.like(selector.property(), text, MatchMode.ANYWHERE));
	criteria.addOrder(Order.desc("count"));
	criteria.setMaxResults(5);
	criteria.setResultTransformer(Transformers.aliasToBean(Suggestion.class));
	return criteria.list();
}}}

!!!UserType
Durch Implementieren von org.hibernate.usertype.UserType können Mapper für [eigene Datentypen|Hibernate EnumSet] geschrieben werden. Hibernate konvertiert diese dann von/zu primitiven Datenbanktypen.

Ein UserType kann auch automatisch angewandt werden, indem er mit entsprechenden Annotationen versehen wird:

{{{
@MappedSuperclass
@TypeDef(defaultForType = EnumSet.class, typeClass = EnumSetType.class)
public class EnumSetType<Type extends Enum<Type>> implements UserType, ParameterizedType {
    ...
}
}}}