Java Reference
In-Depth Information
A stateless session bean class is annotated with the @Stateless annotation. In the
session bean class, an entity bean is created with the create() method. For example,
the create() method corresponding to the identifier property catalogId is
as follows:
public void create(String catalogId)
{ CatalogBean catalogBean = new CatalogBean(catalogId);
em.persist(catalogBean);
}
The create() method is a custom method as opposed to the create() method
of the EJB 2.0 specification; the method naming in the session bean fa├žade may be
modified. The persist() method of the EntityManager class saves a new entity in
the database. The remove() method of the EntityManager class is used to remove
an entity:
public void remove(CatalogBean catalogBean) {
em.remove(catalogBean);
}
The find() method of the EntityManager class is used to find an entity bean.
In the session EJB, add finder methods for the named queries defined in the EJB
bean class. The createNamedQuery() method is used to obtain a query object for a
named query. For example, the finder method corresponding to the named query
FindByCatalogId , which is defined in the entity class, is as follows:
public CatalogBean findByCatalogId(java.lang.String param1)
{Query query=em.createNamedQuery("FindByCatalogId");
query.setParameter(0, param1);
return (CatalogBean)(query.getSingleResult());
}
In the findByCatalogId() method, a javax.persistence.Query object is obtained
from the named query FindByCatalogId . The parameter values are set on the query
object. An entity EJB bean instance is obtained with the getSingleResult() method
of the query object. The named query FindByCatalogId returns a single entity of
the entity EJB bean. A named query may also return a collection of entities. For
example, the named query FindByJournal returns a collection. The finder method
corresponding to the FindByJournal named query is as follows.
public java.util.List<CatalogBean> findByJournal(java.lang.String
param1)
{ Query query= em.createNamedQuery("FindByJournal");
query.setParameter(0, param1);
 
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