/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * 
 * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
 * 
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License. You can obtain
 * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
 * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 * 
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
 * Sun designates this particular file as subject to the "Classpath" exception
 * as provided by Sun in the GPL Version 2 section of the License file that
 * accompanied this code.  If applicable, add the following below the License
 * Header, with the fields enclosed by brackets [] replaced by your own
 * identifying information: "Portions Copyrighted [year]
 * [name of copyright owner]"
 * 
 * Contributor(s):
 * 
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 */
package javax.persistence;

import java.lang.annotation.Target;
import java.lang.annotation.Retention;
import javax.persistence.CascadeType;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import static javax.persistence.FetchType.LAZY;

/**
 * Defines a many-valued association with many-to-many multiplicity. 
 * If the Collection is defined using generics to specify the element 
 * type, the associated target entity class does not need to be 
 * specified; otherwise it must be specified.
 *
 * <p> Every many-to-many association has two sides, the owning 
 * side and the non-owning, or inverse, side.  The join table is 
 * specified on the owning side. If the association is bidirectional, 
 * either side may be designated as the owning side.
 *
 * <p> The same annotation elements for the {@link OneToMany} 
 * annotation apply to the <code>ManyToMany</code> annotation. 
 *
 * <pre>
 *
 *    Example 1:
 *
 *    In Customer class:
 *
 *    &#064;ManyToMany
 *    &#064;JoinTable(name="CUST_PHONES")
 *    public Set<PhoneNumber> getPhones() { return phones; }
 *
 *    In PhoneNumber class:
 *
 *    &#064;ManyToMany(mappedBy="phones")
 *    public Set<Customer> getCustomers() { return customers; }
 *
 *    Example 2:
 *
 *    In Customer class:
 *
 *    &#064;ManyToMany(targetEntity=com.acme.PhoneNumber.class)
 *    public Set getPhones() { return phones; }
 *
 *    In PhoneNumber class:
 *
 *    &#064;ManyToMany(targetEntity=com.acme.Customer.class, mappedBy="phones")
 *    public Set getCustomers() { return customers; }
 *
 *    Example 3:
 *
 *    In Customer class:
 *
 *    &#064;ManyToMany
 *    &#064;JoinTable(name="CUST_PHONE",
 *        joinColumns=
 *            &#064;JoinColumn(name="CUST_ID", referencedColumnName="ID"),
 *        inverseJoinColumns=
 *            &#064;JoinColumn(name="PHONE_ID", referencedColumnName="ID")
 *        )
 *    public Set<PhoneNumber> getPhones() { return phones; }
 *
 *    In PhoneNumberClass:
 *
 *    &#064;ManyToMany(mappedBy="phones")
 *    public Set<Customer> getCustomers() { return customers; }
 * </pre>
 *
 * @since Java Persistence 1.0
 */
@Target({METHOD, FIELD}) 
@Retention(RUNTIME)

public @interface ManyToMany {

    /**
     * (Optional) The entity class that is the target
     * of the association. Optional only if the collection
     * property is defined using Java generics.
     * Must be specified otherwise.
     *
     * <p> Defaults to the parameterized type of
     * the collection when defined using generics.
     */
    Class targetEntity() default void.class;

    /** 
     * (Optional) The operations that must be cascaded to 
     * the target of the association.
     * <p> Defaults to no operations being cascaded.
     */
    CascadeType[] cascade() default {};

    /** (Optional) Whether the association should be
     * lazily loaded or must be eagerly fetched. The
     * {@link FetchType#EAGER EAGER} strategy is a 
     * requirement on the persistenceprovider runtime 
     * that the associatedentities must be eagerly fetched. 
     * The {@link FetchType#LAZY LAZY} strategy is a hint 
     * to the persistence provider runtime.
     */
    FetchType fetch() default LAZY;

    /** 
     * The field that owns the relationship. Required unless 
     * the relationship is unidirectional.
     */
    String mappedBy() default "";
}