001/*
002 * Copyright 2006-2008 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.batch.item.database.support;
018
019/**
020 * H2 implementation of a {@link org.springframework.batch.item.database.PagingQueryProvider} using database specific features.
021 *
022 * @author Dave Syer
023 * @since 2.1
024 */
025public class H2PagingQueryProvider extends AbstractSqlPagingQueryProvider {
026
027        @Override
028        public String generateFirstPageQuery(int pageSize) {
029                return SqlPagingQueryUtils.generateTopSqlQuery(this, false, buildTopClause(pageSize));
030        }
031
032        @Override
033        public String generateRemainingPagesQuery(int pageSize) {
034                return SqlPagingQueryUtils.generateTopSqlQuery(this, true, buildTopClause(pageSize));
035        }
036
037        private String buildTopClause(int pageSize) {
038                return new StringBuilder().append("TOP ").append(pageSize).toString();
039        }
040
041        @Override
042        public String generateJumpToItemQuery(int itemIndex, int pageSize) {
043                int page = itemIndex / pageSize;
044                int offset = (page * pageSize) - 1;
045                offset = offset<0 ? 0 : offset;
046
047                String topClause = new StringBuilder().append("LIMIT ").append(offset).append(" 1").toString();
048                return SqlPagingQueryUtils.generateTopJumpToQuery(this, topClause);
049        }
050
051}