Java tutorial
/******************************************************************************* * Copyright (c) 2008 - 2015 Oracle Corporation. 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. * * Contributors: * Petros Splinakis - Java Persistence 2.2 * Linda DeMichiel - Java Persistence 2.0 - Version 2.0 (October 1 - 2013) * Specification available from http://jcp.org/en/jsr/detail?id=317 * ******************************************************************************/ package javax.persistence; import java.lang.annotation.Repeatable; import java.lang.annotation.Target; import java.lang.annotation.Retention; import static java.lang.annotation.ElementType.TYPE; import static java.lang.annotation.ElementType.METHOD; import static java.lang.annotation.ElementType.FIELD; import static java.lang.annotation.RetentionPolicy.RUNTIME; import static javax.persistence.ConstraintMode.PROVIDER_DEFAULT; /** * Used to override a mapping for an entity relationship. * * <p> May be applied to an entity that extends a mapped superclass to * override a relationship mapping defined by the mapped * superclass. If not specified, the association is mapped the same as * in the original mapping. When used to override a mapping defined by * a mapped superclass, <code>AssociationOverride</code> is applied to * the entity class. * * <p> May be used to override a relationship mapping from an * embeddable within an entity to another entity when the embeddable * is on the owning side of the relationship. When used to override a * relationship mapping defined by an embeddable class (including an * embeddable class embedded within another embeddable class), * <code>AssociationOverride</code> is applied to the field or * property containing the embeddable. * * <p> When <code>AssociationOverride</code> is used to override a * relationship mapping from an embeddable class, the * <code>name</code> element specifies the referencing relationship * field or property within the embeddable class. To override mappings * at multiple levels of embedding, a dot (".") notation syntax must * be used in the <code>name</code> element to indicate an attribute * within an embedded attribute. The value of each identifier used * with the dot notation is the name of the respective embedded field * or property. * * <p> When <code>AssociationOverride</code> is applied to override * the mappings of an embeddable class used as a map value, * "<code>value.</code>" must be used to prefix the name of the * attribute within the embeddable class that is being overridden in * order to specify it as part of the map value. * * <p> If the relationship mapping is a foreign key mapping, the * <code>joinColumns</code> element is used. If the relationship * mapping uses a join table, the <code>joinTable</code> element must * be specified to override the mapping of the join table and/or its * join columns. * * <pre> * Example 1: Overriding the mapping of a relationship defined by a mapped superclass * * @MappedSuperclass * public class Employee { * ... * @ManyToOne * protected Address address; * ... * } * * @Entity * @AssociationOverride(name="address", * joinColumns=@JoinColumn(name="ADDR_ID")) * // address field mapping overridden to ADDR_ID foreign key * public class PartTimeEmployee extends Employee { * ... * } * </pre> * * <pre> * Example 2: Overriding the mapping for phoneNumbers defined in the ContactInfo class * * @Entity * public class Employee { * @Id int id; * @AssociationOverride( * name="phoneNumbers", * joinTable=@JoinTable( * name="EMPPHONES", * joinColumns=@JoinColumn(name="EMP"), * inverseJoinColumns=@JoinColumn(name="PHONE") * ) * ) * @Embedded ContactInfo contactInfo; * ... * } * * @Embeddable * public class ContactInfo { * @ManyToOne Address address; // Unidirectional * @ManyToMany(targetEntity=PhoneNumber.class) List phoneNumbers; * } * * @Entity * public class PhoneNumber { * @Id int number; * @ManyToMany(mappedBy="contactInfo.phoneNumbers") * Collection<Employee> employees; * } * </pre> * * @see Embedded * @see Embeddable * @see MappedSuperclass * @see AttributeOverride * * @since Java Persistence 1.0 */ @Repeatable(AssociationOverrides.class) @Target({ TYPE, METHOD, FIELD }) @Retention(RUNTIME) public @interface AssociationOverride { /** * (Required) The name of the relationship property whose mapping is * being overridden if property-based access is being used, * or the name of the relationship field if field-based access is used. */ String name(); /** * The join column(s) being mapped to the persistent attribute(s). * The <code>joinColumns</code> elements must be specified if a * foreign key mapping is used in the overriding of the mapping of * the relationship. The <code>joinColumns</code> element must * not be specified if a join table is used in the overriding of * the mapping of the relationship. */ JoinColumn[] joinColumns() default {}; /** * (Optional) Used to specify or control the generation of a * foreign key constraint for the columns corresponding to the * <code>joinColumns</code> element when table generation is in * effect. If both this element and the <code>foreignKey</code> * element of any of the <code>joinColumns</code> elements are * specified, the behavior is undefined. If no foreign key * annotation element is specified in either location, the * persistence provider's default foreign key strategy will * apply. * * @since Java Persistence 2.1 */ ForeignKey foreignKey() default @ForeignKey(PROVIDER_DEFAULT); /** * The join table that maps the relationship. * The <code>joinTable</code> element must be specified if a join table * is used in the overriding of the mapping of the * relationship. The <code>joinTable</code> element must not be specified * if a foreign key mapping is used in the overriding of * the relationship. * * @since Java Persistence 2.0 */ JoinTable joinTable() default @JoinTable; }