A new article on OnJava.com takes a look at configuring Hibernate via annotations. Traditionally developers have either configured Hibernate with XML files separate from Java classes or with XDoclet comments in the Java code with in turn generate XML. The article first introduces the concept of annotations mentioning that they support the new EJB3 persistence specification as well as providing a few Hibernate specific extensions. It then walks you through providing annotations to a basic class that a developer would want to persist via Hibernate:
@NamedQueries(
{
@NamedQuery(
name="planeType.findById",
query="select p from PlaneType p left join fetch p.modelPlanes where id=:id"
),
@NamedQuery(
name="planeType.findAll",
query="select p from PlaneType p"
),
@NamedQuery(
name="planeType.delete",
query="delete from PlaneType where id=:id"
)
}
)
@Entity
@Table(name="T_MODEL_PLANE")
public class ModelPlane {
private Long id;
private String name;
@Id
@Column(name="PLANE_ID")
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
@Column(name="PLANE_NAME")
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@ManyToOne( cascade = {CascadeType.PERSIST, CascadeType.MERGE} )
public PlaneType getPlaneType() {
return planeType;
}
}
Important elements such a primary key generate, many to one relationships, and named queries are also covered.