When using spring and spring managed transactions never mess around with the hibernate.current_session_context_class property UNLESS you are using JTA.
Criteria queries allow for multiple root level objects. Caution should be used when doing this, as it can result in Cartesian products of the two table. The where clause should ensure the two objects are joined in some way.
// Select the employees and the mailing addresses that have the same address.
CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
CriteriaQuery criteriaQuery = criteriaBuilder.createQuery();
Root employee = criteriaQuery.from(Employee.class);
Root address = criteriaQuery.from(MailingAddress.class);
criteriaQuery.multiselect(employee, address);
criteriaQuery.where(criteriaBuilder.equal(employee.get("address"), address.get("address"));
Query query = entityManager.createQuery(criteriaQuery);
List<Object[]> result = query.getResultList();
What is Ebean?
Ebean is a Object Relational Mapping Persistence Layer written in Java (Open Source LGPL license).
* Providing the features of EJB3's JPA (and more)
* No container required
* JPA compatible ORM mapping (@Entity, @OneToMany, ...)
Why use Ebean?
Ebean provides a simpler approach to Object Relational Mapping. It does this by not requiring session objects such as JPA EntityManager, JDO PersistenceManager, Hibernate Session, Toplink ClientSession.
The Eclipse Persistence Services Project (EclipseLink) project's goal is to provide a complete persistence framework that is both comprehensive and universal. It will run in any Java environment and read and write objects to virtually any type of data source, including relational databases, XML, or EIS systems. EclipseLink will focus on providing leading edge support, including advanced feature extensions, for the dominant persistence standards for each target data source; Java Persistence API (JPA) for relational databases, Java Architecture for XML Binding (JAXB) for XML, J2EE Connector Architecture (JCA) for EIS and other types of legacy systems, and Service Data Objects (SDO).
EasyBeans is an open-source Enterprise Java Beans (EJB) container hosted by the OW2 consortium. The License used by EasyBeans is the LGPL.
EasyBeans main goal is to ease the development of Enterprise Java Beans. It uses some new architecture design like the bytecode injection (with ASM ObjectWeb tool), IoC, POJO and can be embedded in OSGi bundles or other frameworks (Spring, Eclipse plugins, etc.).
It aims to provide an EJB3 container as specified in the Java Platform Enterprise Edition (Java EE) in its fifth version. It means that Session beans (Stateless or Stateful), Message Driven Beans (MDB) are available on EasyBeans.
The new persistence layer used by EJB 3.0 is now called Java Persistence API (or JPA). It replaces the CMP (Container Managed Persistence) model used by EJB 2.x. The default persistence provider used in EasyBeans is Hibernate Entity Manager or Apache OpenJPA but other JPA providers have been tested like for example Oracle TopLink Essentials.
In the perfect world, your object model would map seamlessly to your database schema. Most organizations however, have database naming standards, requirements for how relationships are modeled and columns that all tables must have.