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The Java Persistence API (JPA) : a standard interface-based Java model abstraction of persistence, developed by the JCP.

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/*
 * Copyright (c) 2008, 2009, 2011 Oracle, Inc. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.  The Eclipse Public License is available
 * at http://www.eclipse.org/legal/epl-v10.html and the Eclipse Distribution License
 * is available at http://www.eclipse.org/org/documents/edl-v10.php.
 */
package javax.persistence;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

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 AttributeOverride and
 * 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) { ... }
 *    }
 * 
 *
 * @see AttributeOverride
 * @see AssociationOverride
 * @since Java Persistence 1.0
 */
@Documented
@Target({TYPE})
@Retention(RUNTIME)
public @interface MappedSuperclass {
}