javax.persistence.MappedSuperclass Maven / Gradle / Ivy
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package javax.persistence;
import java.lang.annotation.Target;
import java.lang.annotation.Retention;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
/**
* Designates a class whose mapping information is applied
* to the entities that inherit from it. A mapped superclass
* has no separate table defined for it.
*
* A class designated with the MappedSuperclass
* annotation can be mapped in the same way as an entity except that the
* mappings will apply only to its subclasses since no table
* exists for the mapped superclass itself. When applied to the
* subclasses the inherited mappings will apply in the context
* of the subclass tables. Mapping information may be overridden
* in such subclasses by using the {@link AttributeOverride} and
* {@link AssociationOverride} annotations or corresponding XML elements.
*
*
* Example: Concrete class as a mapped superclass
*
* @MappedSuperclass
* public class Employee {
*
* @Id protected Integer empId;
* @Version protected Integer version;
* @ManyToOne @JoinColumn(name="ADDR")
* protected Address address;
*
* public Integer getEmpId() { ... }
* public void setEmpId(Integer id) { ... }
* public Address getAddress() { ... }
* public void setAddress(Address addr) { ... }
* }
*
* // Default table is FTEMPLOYEE table
* @Entity
* public class FTEmployee extends Employee {
*
* // Inherited empId field mapped to FTEMPLOYEE.EMPID
* // Inherited version field mapped to FTEMPLOYEE.VERSION
* // Inherited address field mapped to FTEMPLOYEE.ADDR fk
*
*
* // Defaults to FTEMPLOYEE.SALARY
*
* protected Integer salary;
*
*
* public FTEmployee() {}
*
*
* public Integer getSalary() { ... }
*
* public void setSalary(Integer salary) { ... }
* }
*
* @Entity @Table(name="PT_EMP")
* @AssociationOverride(name="address",
*
*
* joincolumns=@JoinColumn(name="ADDR_ID"))
* public class PartTimeEmployee extends Employee {
*
* // Inherited empId field mapped to PT_EMP.EMPID
* // Inherited version field mapped to PT_EMP.VERSION
* // address field mapping overridden to PT_EMP.ADDR_ID fk
* @Column(name="WAGE")
* protected Float hourlyWage;
*
* public PartTimeEmployee() {}
*
* public Float getHourlyWage() { ... }
* public void setHourlyWage(Float wage) { ... }
* }
*
* Example: Non-entity superclass
*
* public class Cart {
*
* // This state is transient
* Integer operationCount;
*
* public Cart() { operationCount = 0; }
* public Integer getOperationCount() { return operationCount; }
* public void incrementOperationCount() { operationCount++; }
* }
*
* @Entity
* public class ShoppingCart extends Cart {
*
* Collection- items = new Vector
- ();
*
* public ShoppingCart() { super(); }
*
*
* ...
*
* @OneToMany
* public Collection
- getItems() { return items; }
* public void addItem(Item item) {
* items.add(item);
* incrementOperationCount();
* }
* }
*
*
* @since Java Persistence 1.0
*/
@Target({TYPE})
@Retention(RUNTIME)
public @interface MappedSuperclass {
}