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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *     http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  package javax.jdo.annotations;
18  
19  import java.lang.annotation.ElementType;
20  import java.lang.annotation.Retention;
21  import java.lang.annotation.RetentionPolicy;
22  import java.lang.annotation.Target;
23  
24  /**
25   * Annotation for a database unique constraint. Used for database schema
26   * generation to create unique constraints. Also used to reorder database
27   * operations when flushing changes to avoid unique constraint violations.
28   * Corresponds to the xml element "unique".
29   *
30   * @version 2.1
31   * @since 2.1
32   */
33  @Target({ElementType.TYPE, ElementType.FIELD, ElementType.METHOD}) 
34  @Retention(RetentionPolicy.RUNTIME)
35  public @interface Unique
36  {
37      /** Name of the unique constraint.
38       * @return the name of the unique constraint
39       */
40      String name() default "";
41  
42      /** Table for the unique constraint. This is needed iff annotating a type 
43       * where this unique constraint is not for the primary table for 
44       * the persistent class or interface.
45       * @return the table on which the unique constraint is defined
46       */
47      String table() default "";
48  
49      /** Whether this unique constraint is deferred until commit.
50       * @return whether this unique constraint is deferred until commit
51       */
52      String deferred() default "";
53  
54      /** Member (field and property) names that compose this unique constraint.
55       * @return member names that compose this unique constraint
56       */
57      String[] members() default {};
58  
59      /** Columns that compose this unique constraint.
60       * @return columns that compose this unique constraint
61       */
62      Column[] columns() default {};
63  }