JPA entities - EJB 3 in Action - page 348

The @Access annotation must first be defined at the class level to set the default access
type for the entire entity. The access types may be either AccessType.FIELD or Ac-
cessType.PROPERTY . Here's an example of setting the User entity access type to
FIELD :
@Entity
@Access(FIELD)
public class User { ... }
You can now define the Seller entity and do some special things:
@Entity
@Access(FIELD)
public class Seller extends User {
//...the rest of seller omitted for brevity
@Transient
private double creditWorth;
@Column(name="CREDIT_WORTH")
@Access(AccessType.PROPERTY)
public double getCreditWorth() { return creditWorth; }
public void setCreditWorth(double cw) {
creditWorth = (cw <= 0) ? 50.0 : cw;
}
}
Notice that the Seller entity uses the @Access annotation to set FIELD as the default
for the class. But it uses @Transient and @Access to override field-based access for
creditWorth in favor of property-based access. Everything else in Seller will be
field-based access except for creditWorth . When performing an override like this, you
always use @Transient and @Access together. This prevents JPA from basically try-
ing to map creditWorth twice.
In the preceding example the default for Seller was field-based access and you per-
formed an override for creditWorth to be property-based access. But this could just as
easily have been the other way around. The default for Seller can be PROPERTY and
the override for creditWorth can make it field-based access. Here's what that would
look like:
@Entity
@Access(PROPERTY)
public class Seller extends User {
//...the rest of seller omitted for brevity
@Column(name="CREDIT_WORTH")