001/* 002 * Copyright 2002-2019 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.jdbc.support; 018 019import java.util.List; 020import java.util.Map; 021 022import org.springframework.dao.InvalidDataAccessApiUsageException; 023import org.springframework.lang.Nullable; 024 025/** 026 * Interface for retrieving keys, typically used for auto-generated keys 027 * as potentially returned by JDBC insert statements. 028 * 029 * <p>Implementations of this interface can hold any number of keys. 030 * In the general case, the keys are returned as a List containing one Map 031 * for each row of keys. 032 * 033 * <p>Most applications only use one key per row and process only one row at a 034 * time in an insert statement. In these cases, just call {@code getKey} 035 * to retrieve the key. The returned value is a Number here, which is the 036 * usual type for auto-generated keys. 037 * 038 * @author Thomas Risberg 039 * @author Juergen Hoeller 040 * @since 1.1 041 * @see org.springframework.jdbc.core.JdbcTemplate 042 * @see org.springframework.jdbc.object.SqlUpdate 043 */ 044public interface KeyHolder { 045 046 /** 047 * Retrieve the first item from the first map, assuming that there is just 048 * one item and just one map, and that the item is a number. 049 * This is the typical case: a single, numeric generated key. 050 * <p>Keys are held in a List of Maps, where each item in the list represents 051 * the keys for each row. If there are multiple columns, then the Map will have 052 * multiple entries as well. If this method encounters multiple entries in 053 * either the map or the list meaning that multiple keys were returned, 054 * then an InvalidDataAccessApiUsageException is thrown. 055 * @return the generated key as a number 056 * @throws InvalidDataAccessApiUsageException if multiple keys are encountered 057 */ 058 @Nullable 059 Number getKey() throws InvalidDataAccessApiUsageException; 060 061 /** 062 * Retrieve the first map of keys. 063 * <p>If there are multiple entries in the list (meaning that multiple rows 064 * had keys returned), then an InvalidDataAccessApiUsageException is thrown. 065 * @return the Map of generated keys for a single row 066 * @throws InvalidDataAccessApiUsageException if keys for multiple rows are encountered 067 */ 068 @Nullable 069 Map<String, Object> getKeys() throws InvalidDataAccessApiUsageException; 070 071 /** 072 * Return a reference to the List that contains the keys. 073 * <p>Can be used for extracting keys for multiple rows (an unusual case), 074 * and also for adding new maps of keys. 075 * @return the List for the generated keys, with each entry representing 076 * an individual row through a Map of column names and key values 077 */ 078 List<Map<String, Object>> getKeyList(); 079 080}