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

import static java.lang.annotation.ElementType.ANNOTATION_TYPE;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

/**
 * Specifies the table that is used for the mapping of collections of basic or embeddable types. Applied to
 * the collection-valued field or property.
 * 
 * By default, the columns of the collection table that correspond to the embeddable class or basic type are
 * derived from the attributes of the embeddable class or from the basic type according to the default values
 * of the Column annotation. In the case of a basic type, the column name is derived from the
 * name of the collection-valued field or property. In the case of an embeddable class, the column names are
 * derived from the field or property names of the embeddable class.
 * 

 * To override the default properties of the column used for a basic type, the Column
 * annotation is used on the collection-valued attribute in addition to the ElementCollection
 * annotation.
 * 
To override these defaults for an embeddable class, the AttributeOverride and/or
 * AttributeOverrides annotations can be used in addition to the ElementCollection
 * annotation. If the embeddable class contains references to other entities, the default values for the
 * columns corresponding to those references may be overridden by means of the
 * AssociationOverride and/or AssociationOverrides annotations.
 * 
 * 
 * If the CollectionTable annotation is missing, the default values of the
 * CollectionTable annotation elements apply.
 *
 * 
 *    Example:
 * 
 *    @Embeddable public class Address {
 *       protected String street;
 *       protected String city;
 *       protected String state;
 *       ...
 *     }
 * 
 *    @Entity public class Person {
 *       @Id protected String ssn;
 *       protected String name;
 *       protected Address home;
 *       ...
 *       @ElementCollection  // use default table (PERSON_NICKNAMES)
 *       @Column(name="name", length=50)
 *       protected Set<String> nickNames = new HashSet();
 *       ...
 *    }
 * 
 *    @Entity public class WealthyPerson extends Person {
 *       @ElementCollection
 *       @CollectionTable(name="HOMES") // use default join column name
 *       @AttributeOverrides({
 *          @AttributeOverride(name="street",
 *                             column=@Column(name="HOME_STREET")),
 *          @AttributeOverride(name="city",
 *                             column=@Column(name="HOME_CITY")),
 *          @AttributeOverride(name="state",
 *                             column=@Column(name="HOME_STATE"))
 *        })
 *       protected Set<Address> vacationHomes = new HashSet();
 *       ...
 *    }
 * 
 * @see ElementCollection
 * @see AttributeOverride
 * @see AssociationOverride
 * @see Column
 * @since Java Persistence 2.0
 */
@Target({ANNOTATION_TYPE, METHOD, FIELD})
@Retention(RUNTIME)
public @interface CollectionTable
{
    /**
     * (Optional) The name of the collection table. If not specified, it defaults to the concatenation of the
     * name of the containing entity and the name of the collection attribute, separated by an underscore.
     * @return name
     */
    String name() default "";

    /**
     * (Optional) The catalog of the table. If not specified, the default catalog is used.
     * @return catalog
     */
    String catalog() default "";

    /**
     * (Optional) The schema of the table. If not specified, the default schema for the user is used.
     * @return schema
     */
    String schema() default "";

    /**
     * (Optional) The foreign key columns of the collection table which reference the primary table of the
     * entity. The default only applies if a single join column is used. The default is the same as for
     * JoinColumn (i.e., the concatenation of the following: the name of the entity; "_"; the
     * name of the referenced primary key column.) However, if there is more than one join column, a
     * JoinColumn annotation must be specified for each join column using the
     * JoinColumns annotation. In this case, both the name and the
     * referencedColumnName elements must be specified in each such JoinColumn
     * annotation.
     * @return join columns
     */
    JoinColumn[] joinColumns() default {};

    /**
     * (Optional) Unique constraints that are to be placed on the table. These are only used if table
     * generation is in effect.
     * @return unique constraints
     */
    UniqueConstraint[] uniqueConstraints() default {};

    /**
     * (Optional) Indexes for the table. These are only used if table generation is in effect.
     * @return The indexes
     */
    Index[] indexes() default {};

    /**
     * (Optional) Used to specify or control the generation of a foreign key constraint for the columns
     * corresponding to the joinColumns element when table generation is in effect. If both this element and
     * the foreignKey element of any of the joinColumns 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
     * @return FK
     */
    ForeignKey foreignKey() default @ForeignKey(ConstraintMode.PROVIDER_DEFAULT);
}