/*
* Copyright 2006-2012 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.batch.item.database.support;
import javax.sql.DataSource;
import org.springframework.batch.item.database.PagingQueryProvider;
import org.springframework.dao.InvalidDataAccessResourceUsageException;
import org.springframework.jdbc.support.JdbcUtils;
/**
* Derby implementation of a {@link PagingQueryProvider} using standard SQL:2003 windowing functions.
* These features are supported starting with Apache Derby version 10.4.1.3.
*
* As the OVER() function does not support the ORDER BY clause a sub query is instead used to order the results
* before the ROW_NUM restriction is applied
*
* @author Thomas Risberg
* @author David Thexton
* @author Michael Minella
* @since 2.0
*/
public class DerbyPagingQueryProvider extends SqlWindowingPagingQueryProvider {
private static final String MINIMAL_DERBY_VERSION = "10.4.1.3";
@Override
public void init(DataSource dataSource) throws Exception {
super.init(dataSource);
String version = JdbcUtils.extractDatabaseMetaData(dataSource, "getDatabaseProductVersion").toString();
if (!isDerbyVersionSupported(version)) {
throw new InvalidDataAccessResourceUsageException("Apache Derby version " + version + " is not supported by this class, Only version " + MINIMAL_DERBY_VERSION + " or later is supported");
}
}
// derby version numbering is M.m.f.p [ {alpha|beta} ] see http://db.apache.org/derby/papers/versionupgrade.html#Basic+Numbering+Scheme
private boolean isDerbyVersionSupported(String version) {
String[] minimalVersionParts = MINIMAL_DERBY_VERSION.split("\\.");
String[] versionParts = version.split("[\\. ]");
for (int i = 0; i < minimalVersionParts.length; i++) {
int minimalVersionPart = Integer.valueOf(minimalVersionParts[i]);
int versionPart = Integer.valueOf(versionParts[i]);
if (versionPart < minimalVersionPart) {
return false;
} else if (versionPart > minimalVersionPart) {
return true;
}
}
return true;
}
@Override
protected String getOrderedQueryAlias() {
return "TMP_ORDERED";
}
@Override
protected String getOverClause() {
return "";
}
@Override
protected String getOverSubstituteClauseStart() {
return " FROM (SELECT " + getSelectClause();
}
@Override
protected String getOverSubstituteClauseEnd() {
return " ) AS " + getOrderedQueryAlias();
}
}