001: /*
002: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
003: *
004: * Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
005: *
006: * The contents of this file are subject to the terms of either the GNU
007: * General Public License Version 2 only ("GPL") or the Common Development
008: * and Distribution License("CDDL") (collectively, the "License"). You
009: * may not use this file except in compliance with the License. You can obtain
010: * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html
011: * or glassfish/bootstrap/legal/LICENSE.txt. See the License for the specific
012: * language governing permissions and limitations under the License.
013: *
014: * When distributing the software, include this License Header Notice in each
015: * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.
016: * Sun designates this particular file as subject to the "Classpath" exception
017: * as provided by Sun in the GPL Version 2 section of the License file that
018: * accompanied this code. If applicable, add the following below the License
019: * Header, with the fields enclosed by brackets [] replaced by your own
020: * identifying information: "Portions Copyrighted [year]
021: * [name of copyright owner]"
022: *
023: * Contributor(s):
024: *
025: * If you wish your version of this file to be governed by only the CDDL or
026: * only the GPL Version 2, indicate your decision by adding "[Contributor]
027: * elects to include this software in this distribution under the [CDDL or GPL
028: * Version 2] license." If you don't indicate a single choice of license, a
029: * recipient has the option to distribute your version of this file under
030: * either the CDDL, the GPL Version 2 or to extend the choice of license to
031: * its licensees as provided above. However, if you add GPL Version 2 code
032: * and therefore, elected the GPL Version 2 license, then the option applies
033: * only if the new code is made subject to such option by the copyright
034: * holder.
035: */
036: package javax.persistence;
037:
038: import java.lang.annotation.Target;
039: import java.lang.annotation.Retention;
040: import static java.lang.annotation.ElementType.TYPE;
041: import static java.lang.annotation.RetentionPolicy.RUNTIME;
042: import static javax.persistence.DiscriminatorType.STRING;
043:
044: /**
045: * Is used to define the discriminator column for the
046: * {@link InheritanceType#SINGLE_TABLE SINGLE_TABLE} and
047: * {@link InheritanceType#JOINED JOINED} inheritance mapping strategies.
048: *
049: * <p> The strategy and the discriminator column are only
050: * specified in the root of an entity class hierarchy or
051: * subhierarchy in which a different inheritance strategy is applied
052: *
053: * <p> If the <code>DiscriminatorColumn</code> annotation is missing,
054: * and a discriminator column is required, the name of the
055: * discriminator column defaults to <code>"DTYPE"</code> and the discriminator
056: * type to {@link DiscriminatorType#STRING DiscriminatorType.STRING}.
057: *
058: * <pre>
059: * Example:
060: * @Entity
061: * @Table(name="CUST")
062: * @Inheritance(strategy=SINGLE_TABLE)
063: * @DiscriminatorColumn(name="DISC", discriminatorType=STRING,length=20)
064: * public class Customer { ... }
065: *
066: * @Entity
067: * public class ValuedCustomer extends Customer { ... }
068: * </pre>
069: *
070: * @since Java Persistence 1.0
071: */
072: @Target({TYPE})
073: @Retention(RUNTIME)
074: public @interface DiscriminatorColumn {
075:
076: /**
077: * (Optional) The name of column to be used for the discriminator.
078: */
079: String name() default "DTYPE";
080:
081: /**
082: * (Optional) The type of object/column to use as a class discriminator.
083: * Defaults to {@link DiscriminatorType#STRING DiscriminatorType.STRING}.
084: */
085: DiscriminatorType discriminatorType() default STRING;
086:
087: /**
088: * (Optional) The SQL fragment that is used when generating the DDL
089: * for the discriminator column.
090: * <p> Defaults to the provider-generated SQL to create a column
091: * of the specified discriminator type.
092: */
093: String columnDefinition() default "";
094:
095: /**
096: * (Optional) The column length for String-based discriminator types.
097: * Ignored for other discriminator types.
098: */
099: int length() default 31;
100: }
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