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1   /*
2    * Copyright 2006-2012 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  import org.springframework.batch.item.database.PagingQueryProvider;
20  import org.springframework.util.StringUtils;
21  
22  /**
23   * MySQL implementation of a {@link PagingQueryProvider} using database specific features.
24   *
25   * @author Thomas Risberg
26   * @author Michael Minella
27   * @since 2.0
28   */
29  public class MySqlPagingQueryProvider extends AbstractSqlPagingQueryProvider {
30  
31  	@Override
32  	public String generateFirstPageQuery(int pageSize) {
33  		return SqlPagingQueryUtils.generateLimitSqlQuery(this, false, buildLimitClause(pageSize));
34  	}
35  
36  	@Override
37  	public String generateRemainingPagesQuery(int pageSize) {
38  		if(StringUtils.hasText(getGroupClause())) {
39  			return SqlPagingQueryUtils.generateLimitGroupedSqlQuery(this, true, buildLimitClause(pageSize));
40  		}
41  		else {
42  			return SqlPagingQueryUtils.generateLimitSqlQuery(this, true, buildLimitClause(pageSize));
43  		}
44  	}
45  
46  	private String buildLimitClause(int pageSize) {
47  		return new StringBuilder().append("LIMIT ").append(pageSize).toString();
48  	}
49  
50  	@Override
51  	public String generateJumpToItemQuery(int itemIndex, int pageSize) {
52  		int page = itemIndex / pageSize;
53  		int offset = (page * pageSize) - 1;
54  		offset = offset<0 ? 0 : offset;
55  
56  		String limitClause = new StringBuilder().append("LIMIT ").append(offset).append(", 1").toString();
57  		return SqlPagingQueryUtils.generateLimitJumpToQuery(this, limitClause);
58  	}
59  
60  }