src/javax/persistence/MappedSuperclass.java

/*
 * Copyright (c) 2008, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0,
 * or the Eclipse Distribution License v. 1.0 which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 */

// Contributors:
//     Linda DeMichiel - Java Persistence 2.1
//     Linda DeMichiel - Java Persistence 2.0


package javax.persistence;

import java.lang.annotation.Target;
import java.lang.annotation.Retention;
import java.lang.annotation.Documented;
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.  
 *
 * <p> A class designated with the <code>MappedSuperclass</code> 
 * 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 <code>AttributeOverride</code> and 
 * <code>AssociationOverride</code> annotations or corresponding XML elements.
 *
 * <pre>
 *    Example: Concrete class as a mapped superclass
 *
 *    &#064;MappedSuperclass
 *    public class Employee {
 *    
 *        &#064;Id protected Integer empId;
 *        &#064;Version protected Integer version;
 *        &#064;ManyToOne &#064;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
 *    &#064;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) { ... }
 *    }
 *    
 *    &#064;Entity &#064;Table(name="PT_EMP")
 *    &#064;AssociationOverride(
 *        name="address", 
 *        joincolumns=&#064;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
 *        &#064;Column(name="WAGE")
 *        protected Float hourlyWage;
 *    
 *        public PartTimeEmployee() {}
 *    
 *        public Float getHourlyWage() { ... }
 *        public void setHourlyWage(Float wage) { ... }
 *    }
 * </pre>
 *
 * @see AttributeOverride 
 * @see AssociationOverride
 * @since Java Persistence 1.0
 */
@Documented
@Target({TYPE})
@Retention(RUNTIME)
public @interface MappedSuperclass {
}