KeyHolder


1   /*
2    * Copyright 2002-2005 the original author or authors.
3    * 
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    * 
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    * 
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package org.springframework.jdbc.support;
18  
19  import java.util.List  ;
20  import java.util.Map  ;
21  
22  import org.springframework.dao.InvalidDataAccessApiUsageException;
23  
24  /** 
25   * Interface for retrieving keys, typically used for auto-generated keys
26   * as potentially returned by JDBC insert statements.
27   *
28   * <p>Implementations of this interface can hold any number of keys.
29   * In the general case, the keys are returned as a List containing one Map
30   * for each row of keys.
31   *
32   * <p>Most applications only use on key per row and process only one row at a
33   * time in an insert statement. In these cases, just call <code>getKey</code>
34   * to retrieve the key. The returned value is a Number here, which is the
35   * usual type for auto-generated keys.
36   *
37   * @author Thomas Risberg
38   * @since 1.1
39   * @see org.springframework.jdbc.core.JdbcTemplate
40   * @see org.springframework.jdbc.object.SqlUpdate
41   */
42  public interface KeyHolder {
43      
44      /** 
45       * Retrieve the first item from the first map, assuming that there is just
46       * one item and just one map, and that the item is a number.
47       * This is the typical case: a single, numeric generated key.
48       * <p>Keys are held in a List of Maps, where each item in the list represents
49       * the keys for each row. If there are multiple columns, then the Map will have
50       * multiple entries as well. If this method encounters multiple entries in
51       * either the map or the list meaning that multiple keys were returned,
52       * then an InvalidDataAccessApiUsageException is thrown.
53       * @return the generated key
54       * @throws InvalidDataAccessApiUsageException if multiple keys are encountered.
55       */
56      Number   getKey() throws InvalidDataAccessApiUsageException; 
57  
58      /** 
59       * Retrieve the first map of keys. If there are multiple entries in the list
60       * (meaning that multiple rows had keys returned), then an
61       * InvalidDataAccessApiUsageException is thrown.
62       * @return the Map of generated keys
63       * @throws InvalidDataAccessApiUsageException if keys for multiple rows are encountered
64       */
65      Map   getKeys() throws InvalidDataAccessApiUsageException; 
66  
67      /** 
68       * Return a reference to the List that contains the keys.
69       * Can be used for extracting keys for multiple rows (an unusual case),
70       * and also for adding new maps of keys.
71       * @return the List for the generated keys, with each entry being a Map
72       * of column names and key values
73       */
74      List   getKeyList();
75  
76  }
77
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