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1   /*
2    * Copyright 2006-2008 the original author or authors.
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package org.springframework.batch.item.database.support;
18  
19  /**
20   * H2 implementation of a {@link org.springframework.batch.item.database.PagingQueryProvider} using database specific features.
21   *
22   * @author Dave Syer
23   * @since 2.1
24   */
25  public class H2PagingQueryProvider extends AbstractSqlPagingQueryProvider {
26  
27  	@Override
28  	public String generateFirstPageQuery(int pageSize) {
29  		return SqlPagingQueryUtils.generateTopSqlQuery(this, false, buildTopClause(pageSize));
30  	}
31  
32  	@Override
33  	public String generateRemainingPagesQuery(int pageSize) {
34  		return SqlPagingQueryUtils.generateTopSqlQuery(this, true, buildTopClause(pageSize));
35  	}
36  
37  	private String buildTopClause(int pageSize) {
38  		return new StringBuilder().append("TOP ").append(pageSize).toString();
39  	}
40  
41  	@Override
42  	public String generateJumpToItemQuery(int itemIndex, int pageSize) {
43  		int page = itemIndex / pageSize;
44  		int offset = (page * pageSize) - 1;
45  		offset = offset<0 ? 0 : offset;
46  
47  		String topClause = new StringBuilder().append("LIMIT ").append(offset).append(" 1").toString();
48  		return SqlPagingQueryUtils.generateTopJumpToQuery(this, topClause);
49  	}
50  
51  }