/*
* Copyright 2002-2008 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.jdbc.support.incrementer;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import javax.sql.DataSource;
import org.springframework.dao.DataAccessException;
import org.springframework.dao.DataAccessResourceFailureException;
import org.springframework.jdbc.datasource.DataSourceUtils;
import org.springframework.jdbc.support.JdbcUtils;
/**
* {@link DataFieldMaxValueIncrementer} that increments the maximum value of a given Derby table
* with the equivalent of an auto-increment column. Note: If you use this class, your Derby key
* column should <i>NOT</i> be defined as an IDENTITY column, as the sequence table does the job.
*
* <p>The sequence is kept in a table. There should be one sequence table per
* table that needs an auto-generated key.
*
* <p>Derby requires an additional column to be used for the insert since it is impossible
* to insert a null into the identity column and have the value generated. This is solved by
* providing the name of a dummy column that also must be created in the sequence table.
*
* <p>Example:
*
* <pre class="code">create table tab (id int not null primary key, text varchar(100));
* create table tab_sequence (value int generated always as identity, dummy char(1));
* insert into tab_sequence (dummy) values(null);</pre>
*
* If "cacheSize" is set, the intermediate values are served without querying the
* database. If the server or your application is stopped or crashes or a transaction
* is rolled back, the unused values will never be served. The maximum hole size in
* numbering is consequently the value of cacheSize.
*
* <b>HINT:</b> Since Derby supports the JDBC 3.0 <code>getGeneratedKeys</code> method,
* it is recommended to use IDENTITY columns directly in the tables and then utilizing
* a {@link org.springframework.jdbc.support.KeyHolder} when calling the with the
* <code>update(PreparedStatementCreator psc, KeyHolder generatedKeyHolder)</code>
* method of the {@link org.springframework.jdbc.core.JdbcTemplate}.
*
* <p>Thanks to Endre Stolsvik for the suggestion!
*
* @author Thomas Risberg
* @author Juergen Hoeller
* @since 2.5
*/
public class DerbyMaxValueIncrementer extends AbstractColumnMaxValueIncrementer {
/** The default for dummy name */
private static final String DEFAULT_DUMMY_NAME = "dummy";
/** The name of the dummy column used for inserts */
private String dummyName = DEFAULT_DUMMY_NAME;
/** The current cache of values */
private long[] valueCache;
/** The next id to serve from the value cache */
private int nextValueIndex = -1;
/**
* Default constructor for bean property style usage.
* @see #setDataSource
* @see #setIncrementerName
* @see #setColumnName
*/
public DerbyMaxValueIncrementer() {
}
/**
* Convenience constructor.
* @param dataSource the DataSource to use
* @param incrementerName the name of the sequence/table to use
* @param columnName the name of the column in the sequence table to use
*/
public DerbyMaxValueIncrementer(DataSource dataSource, String incrementerName, String columnName) {
super(dataSource, incrementerName, columnName);
this.dummyName = DEFAULT_DUMMY_NAME;
}
/**
* Convenience constructor.
* @param dataSource the DataSource to use
* @param incrementerName the name of the sequence/table to use
* @param columnName the name of the column in the sequence table to use
* @param dummyName the name of the dummy column used for inserts
*/
public DerbyMaxValueIncrementer(DataSource dataSource, String incrementerName, String columnName, String dummyName) {
super(dataSource, incrementerName, columnName);
this.dummyName = dummyName;
}
/**
* Set the name of the dummy column.
*/
public void setDummyName(String dummyName) {
this.dummyName = dummyName;
}
/**
* Return the name of the dummy column.
*/
public String getDummyName() {
return this.dummyName;
}
protected synchronized long getNextKey() throws DataAccessException {
if (this.nextValueIndex < 0 || this.nextValueIndex >= getCacheSize()) {
/*
* Need to use straight JDBC code because we need to make sure that the insert and select
* are performed on the same connection (otherwise we can't be sure that last_insert_id()
* returned the correct value)
*/
Connection con = DataSourceUtils.getConnection(getDataSource());
Statement stmt = null;
try {
stmt = con.createStatement();
DataSourceUtils.applyTransactionTimeout(stmt, getDataSource());
this.valueCache = new long[getCacheSize()];
this.nextValueIndex = 0;
for (int i = 0; i < getCacheSize(); i++) {
stmt.executeUpdate("insert into " + getIncrementerName() + " (" + getDummyName() + ") values(null)");
ResultSet rs = stmt.executeQuery("select IDENTITY_VAL_LOCAL() from " + getIncrementerName());
try {
if (!rs.next()) {
throw new DataAccessResourceFailureException("IDENTITY_VAL_LOCAL() failed after executing an update");
}
this.valueCache[i] = rs.getLong(1);
}
finally {
JdbcUtils.closeResultSet(rs);
}
}
long maxValue = this.valueCache[(this.valueCache.length - 1)];
stmt.executeUpdate("delete from " + getIncrementerName() + " where " + getColumnName() + " < " + maxValue);
}
catch (SQLException ex) {
throw new DataAccessResourceFailureException("Could not obtain IDENTITY value", ex);
}
finally {
JdbcUtils.closeStatement(stmt);
DataSourceUtils.releaseConnection(con, getDataSource());
}
}
return this.valueCache[this.nextValueIndex++];
}
}