001/*
002 * Copyright 2002-2014 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.incrementer;
018
019import javax.sql.DataSource;
020
021/**
022 * {@link DataFieldMaxValueIncrementer} that increments the maximum value of a given Derby table
023 * with the equivalent of an auto-increment column. Note: If you use this class, your Derby key
024 * column should <i>NOT</i> be defined as an IDENTITY column, as the sequence table does the job.
025 *
026 * <p>The sequence is kept in a table. There should be one sequence table per
027 * table that needs an auto-generated key.
028 *
029 * <p>Derby requires an additional column to be used for the insert since it is impossible
030 * to insert a null into the identity column and have the value generated.  This is solved by
031 * providing the name of a dummy column that also must be created in the sequence table.
032 *
033 * <p>Example:
034 *
035 * <pre class="code">create table tab (id int not null primary key, text varchar(100));
036 * create table tab_sequence (value int generated always as identity, dummy char(1));
037 * insert into tab_sequence (dummy) values(null);</pre>
038 *
039 * If "cacheSize" is set, the intermediate values are served without querying the
040 * database. If the server or your application is stopped or crashes or a transaction
041 * is rolled back, the unused values will never be served. The maximum hole size in
042 * numbering is consequently the value of cacheSize.
043 *
044 * <b>HINT:</b> Since Derby supports the JDBC 3.0 {@code getGeneratedKeys} method,
045 * it is recommended to use IDENTITY columns directly in the tables and then utilizing
046 * a {@link org.springframework.jdbc.support.KeyHolder} when calling the with the
047 * {@code update(PreparedStatementCreator psc, KeyHolder generatedKeyHolder)}
048 * method of the {@link org.springframework.jdbc.core.JdbcTemplate}.
049 *
050 * <p>Thanks to Endre Stolsvik for the suggestion!
051 *
052 * @author Thomas Risberg
053 * @author Juergen Hoeller
054 * @since 2.5
055 */
056public class DerbyMaxValueIncrementer extends AbstractIdentityColumnMaxValueIncrementer {
057
058        /** The default for dummy name */
059        private static final String DEFAULT_DUMMY_NAME = "dummy";
060
061        /** The name of the dummy column used for inserts */
062        private String dummyName = DEFAULT_DUMMY_NAME;
063
064
065        /**
066         * Default constructor for bean property style usage.
067         * @see #setDataSource
068         * @see #setIncrementerName
069         * @see #setColumnName
070         */
071        public DerbyMaxValueIncrementer() {
072        }
073
074        /**
075         * Convenience constructor.
076         * @param dataSource the DataSource to use
077         * @param incrementerName the name of the sequence/table to use
078         * @param columnName the name of the column in the sequence table to use
079         */
080        public DerbyMaxValueIncrementer(DataSource dataSource, String incrementerName, String columnName) {
081                super(dataSource, incrementerName, columnName);
082                this.dummyName = DEFAULT_DUMMY_NAME;
083        }
084
085        /**
086         * Convenience constructor.
087         * @param dataSource the DataSource to use
088         * @param incrementerName the name of the sequence/table to use
089         * @param columnName the name of the column in the sequence table to use
090         * @param dummyName the name of the dummy column used for inserts
091         */
092        public DerbyMaxValueIncrementer(DataSource dataSource, String incrementerName, String columnName, String dummyName) {
093                super(dataSource, incrementerName, columnName);
094                this.dummyName = dummyName;
095        }
096
097
098        /**
099         * Set the name of the dummy column.
100         */
101        public void setDummyName(String dummyName) {
102                this.dummyName = dummyName;
103        }
104
105        /**
106         * Return the name of the dummy column.
107         */
108        public String getDummyName() {
109                return this.dummyName;
110        }
111
112
113        @Override
114        protected String getIncrementStatement() {
115                return "insert into " + getIncrementerName() + " (" + getDummyName() + ") values(null)";
116        }
117
118        @Override
119        protected String getIdentityStatement() {
120                return "select IDENTITY_VAL_LOCAL() from " + getIncrementerName();
121        }
122
123}