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HsqlMaxValueIncrementer.java
Upload User: jiancairen
Upload Date: 2007-08-27
Package Size: 26458k
Code Size: 5k
Category:
Java Develop
Development Platform:
Java
- /*
- * Copyright 2002-2004 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;
- /**
- * Class to increment maximum value of a given HSQL table with the equivalent
- * of an auto-increment column. Note: If you use this class, your HSQL key
- * column should <i>NOT</i> be auto-increment, 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>Example:
- *
- * <pre>
- * create table tab (id int not null primary key, text varchar(100));
- * create table tab_sequence (value identity);
- * insert into tab_sequence values(0);</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.
- *
- * @author Isabelle Muszynski
- * @author Jean-Pierre Pawlak
- * @author Thomas Risberg
- */
- public class HsqlMaxValueIncrementer extends AbstractDataFieldMaxValueIncrementer {
- /** The name of the column for this sequence */
- private String columnName;
- /** The number of keys buffered in a cache */
- private int cacheSize = 1;
- private long[] valueCache = null;
- /** The next id to serve from the value cache */
- private int nextValueIndex = -1;
- /**
- * Default constructor.
- **/
- public HsqlMaxValueIncrementer() {
- }
- /**
- * Convenience constructor.
- * @param ds 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 HsqlMaxValueIncrementer(DataSource ds, String incrementerName, String columnName) {
- setDataSource(ds);
- setIncrementerName(incrementerName);
- this.columnName = columnName;
- afterPropertiesSet();
- }
- /**
- * Set the name of the column in the sequence table.
- */
- public void setColumnName(String columnName) {
- this.columnName = columnName;
- }
- /**
- * Return the name of the column in the sequence table.
- */
- public String getColumnName() {
- return this.columnName;
- }
- /**
- * Set the number of buffered keys.
- */
- public void setCacheSize(int cacheSize) {
- this.cacheSize = cacheSize;
- }
- /**
- * Return the number of buffered keys.
- */
- public int getCacheSize() {
- return this.cacheSize;
- }
- public void afterPropertiesSet() {
- super.afterPropertiesSet();
- if (this.columnName == null) {
- throw new IllegalArgumentException("columnName is required");
- }
- }
- 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() + " values(null)");
- ResultSet rs = stmt.executeQuery("select max(identity()) from " + getIncrementerName());
- try {
- if (!rs.next()) {
- throw new DataAccessResourceFailureException("identity() 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 " + this.columnName + " < " + maxValue);
- }
- catch (SQLException ex) {
- throw new DataAccessResourceFailureException("Could not obtain identity()", ex);
- }
- finally {
- JdbcUtils.closeStatement(stmt);
- DataSourceUtils.closeConnectionIfNecessary(con, getDataSource());
- }
- }
- return this.valueCache[this.nextValueIndex++];
- }
- }