| 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; |
| 18 | |
| 19 | import org.springframework.util.ClassUtils; |
| 20 | import org.springframework.util.Assert; |
| 21 | import org.springframework.batch.item.ExecutionContext; |
| 22 | import org.springframework.orm.ibatis.SqlMapClientTemplate; |
| 23 | |
| 24 | import java.util.Map; |
| 25 | import java.util.HashMap; |
| 26 | import java.util.concurrent.CopyOnWriteArrayList; |
| 27 | |
| 28 | import com.ibatis.sqlmap.client.SqlMapClient; |
| 29 | |
| 30 | /** |
| 31 | * <p> |
| 32 | * {@link org.springframework.batch.item.ItemReader} for reading database |
| 33 | * records using iBATIS in a paging fashion. |
| 34 | * </p> |
| 35 | * |
| 36 | * <p> |
| 37 | * It executes the query specified as the {@link #setQueryId(String)} to |
| 38 | * retrieve requested data. The query is executed using paged requests of a size |
| 39 | * specified in {@link #setPageSize(int)}. Additional pages are requested when |
| 40 | * needed as {@link #read()} method is called, returning an object corresponding |
| 41 | * to current position. Some standard query parameters are provided by the |
| 42 | * reader and the SQL in the named query must use some or all of these parameters |
| 43 | * (depending on the SQL variant) to construct a result set of the required |
| 44 | * size. The parameters are: |
| 45 | * <ul> |
| 46 | * <li><code>_page</code>: the page number to be read (starting at 0)</li> |
| 47 | * <li><code>_pagesize</code>: the size of the pages, i.e. the number of rows to |
| 48 | * return</li> |
| 49 | * <li><code>_skiprows</code>: the product of <code>_page</code> and |
| 50 | * <code>_pagesize</code></li> |
| 51 | * </ul> |
| 52 | * Failure to write the correct platform-specific SQL often results in an |
| 53 | * infinite loop in the reader because it keeps asking for the next page and |
| 54 | * gets the same result set over and over. |
| 55 | * </p> |
| 56 | * |
| 57 | * <p> |
| 58 | * The performance of the paging depends on the iBATIS implementation. |
| 59 | * Setting a fairly large page size and using a commit interval that matches the |
| 60 | * page size should provide better performance. |
| 61 | * </p> |
| 62 | * |
| 63 | * <p> |
| 64 | * The implementation is thread-safe in between calls to |
| 65 | * {@link #open(ExecutionContext)}, but remember to use |
| 66 | * <code>saveState=false</code> if used in a multi-threaded client (no restart |
| 67 | * available). |
| 68 | * </p> |
| 69 | * |
| 70 | * @author Thomas Risberg |
| 71 | * @author Dave Syer |
| 72 | * @since 2.0 |
| 73 | */ |
| 74 | public class IbatisPagingItemReader<T> extends AbstractPagingItemReader<T> { |
| 75 | |
| 76 | private SqlMapClient sqlMapClient; |
| 77 | |
| 78 | private String queryId; |
| 79 | |
| 80 | private SqlMapClientTemplate sqlMapClientTemplate; |
| 81 | |
| 82 | private Map<String, Object> parameterValues; |
| 83 | |
| 84 | public IbatisPagingItemReader() { |
| 85 | setName(ClassUtils.getShortName(IbatisPagingItemReader.class)); |
| 86 | } |
| 87 | |
| 88 | public void setSqlMapClient(SqlMapClient sqlMapClient) { |
| 89 | this.sqlMapClient = sqlMapClient; |
| 90 | } |
| 91 | |
| 92 | public void setQueryId(String queryId) { |
| 93 | this.queryId = queryId; |
| 94 | } |
| 95 | |
| 96 | /** |
| 97 | * The parameter values to be used for the query execution. |
| 98 | * |
| 99 | * @param parameterValues the values keyed by the parameter named used in |
| 100 | * the query string. |
| 101 | */ |
| 102 | public void setParameterValues(Map<String, Object> parameterValues) { |
| 103 | this.parameterValues = parameterValues; |
| 104 | } |
| 105 | |
| 106 | /** |
| 107 | * Check mandatory properties. |
| 108 | * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet() |
| 109 | */ |
| 110 | public void afterPropertiesSet() throws Exception { |
| 111 | super.afterPropertiesSet(); |
| 112 | Assert.notNull(sqlMapClient); |
| 113 | sqlMapClientTemplate = new SqlMapClientTemplate(sqlMapClient); |
| 114 | Assert.notNull(queryId); |
| 115 | } |
| 116 | |
| 117 | @Override |
| 118 | @SuppressWarnings("unchecked") |
| 119 | protected void doReadPage() { |
| 120 | Map<String, Object> parameters = new HashMap<String, Object>(); |
| 121 | if (parameterValues != null) { |
| 122 | parameters.putAll(parameterValues); |
| 123 | } |
| 124 | parameters.put("_page", getPage()); |
| 125 | parameters.put("_pagesize", getPageSize()); |
| 126 | parameters.put("_skiprows", getPage() * getPageSize()); |
| 127 | if (results == null) { |
| 128 | results = new CopyOnWriteArrayList<T>(); |
| 129 | } |
| 130 | else { |
| 131 | results.clear(); |
| 132 | } |
| 133 | results.addAll(sqlMapClientTemplate.queryForList(queryId, parameters)); |
| 134 | } |
| 135 | |
| 136 | @Override |
| 137 | protected void doJumpToPage(int itemIndex) { |
| 138 | } |
| 139 | |
| 140 | } |