XML isn't for everyone, and so there are some alternative ways to define O/R mapping metadata in Hibernate.
Many Hibernate users prefer to embed mapping information directly in sourcecode using
XDoclet @hibernate.tags
. We will not cover this approach in this
document, since strictly it is considered part of XDoclet. However, we include the
following example of the Cat
class with XDoclet mappings.
package eg; import java.util.Set; import java.util.Date; /** * @hibernate.class * table="CATS" */ public class Cat { private Long id; // identifier private Date birthdate; private Cat mother; private Set kittens private Color color; private char sex; private float weight; /* * @hibernate.id * generator-class="native" * column="CAT_ID" */ public Long getId() { return id; } private void setId(Long id) { this.id=id; } /** * @hibernate.many-to-one * column="PARENT_ID" */ public Cat getMother() { return mother; } void setMother(Cat mother) { this.mother = mother; } /** * @hibernate.property * column="BIRTH_DATE" */ public Date getBirthdate() { return birthdate; } void setBirthdate(Date date) { birthdate = date; } /** * @hibernate.property * column="WEIGHT" */ public float getWeight() { return weight; } void setWeight(float weight) { this.weight = weight; } /** * @hibernate.property * column="COLOR" * not-null="true" */ public Color getColor() { return color; } void setColor(Color color) { this.color = color; } /** * @hibernate.set * inverse="true" * order-by="BIRTH_DATE" * @hibernate.collection-key * column="PARENT_ID" * @hibernate.collection-one-to-many */ public Set getKittens() { return kittens; } void setKittens(Set kittens) { this.kittens = kittens; } // addKitten not needed by Hibernate public void addKitten(Cat kitten) { kittens.add(kitten); } /** * @hibernate.property * column="SEX" * not-null="true" * update="false" */ public char getSex() { return sex; } void setSex(char sex) { this.sex=sex; } }
See the Hibernate web site for more examples of XDoclet and Hibernate.
JDK 5.0 introduced XDoclet-style annotations at the language level, type-safe and
checked at compile time. This mechnism is more powerful than XDoclet annotations and
better supported by tools and IDEs. IntelliJ IDEA, for example, supports auto-completion
and syntax highlighting of JDK 5.0 annotations. The new revision of the EJB specification
(JSR-220) uses JDK 5.0 annotations as the primary metadata mechanism for entity beans.
Hibernate3 implements the EntityManager
of JSR-220 (the persistence API),
support for mapping metadata is available via the Hibernate Annotations
package, as a separate download. Both EJB3 (JSR-220) and Hibernate3 metadata is supported.
This is an example of a POJO class annotated as an EJB entity bean:
@Entity(access = AccessType.FIELD) public class Customer implements Serializable { @Id; Long id; String firstName; String lastName; Date birthday; @Transient Integer age; @Embedded private Address homeAddress; @OneToMany(cascade=CascadeType.ALL) @JoinColumn(name="CUSTOMER_ID") Set<Order> orders; // Getter/setter and business methods }
Note that support for JDK 5.0 Annotations (and JSR-220) is still work in progress and not completed. Please refer to the Hibernate Annotations module for more details.