| 1 | /* |
| 2 | * Copyright 2006-2007 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 | package org.springframework.batch.item.database; |
| 17 | |
| 18 | import org.hibernate.ScrollableResults; |
| 19 | import org.hibernate.Session; |
| 20 | import org.hibernate.SessionFactory; |
| 21 | import org.hibernate.StatelessSession; |
| 22 | import org.springframework.batch.item.ExecutionContext; |
| 23 | import org.springframework.batch.item.ExecutionContextUserSupport; |
| 24 | import org.springframework.batch.item.ItemReader; |
| 25 | import org.springframework.batch.item.ItemStream; |
| 26 | import org.springframework.beans.factory.InitializingBean; |
| 27 | import org.springframework.util.Assert; |
| 28 | import org.springframework.util.ClassUtils; |
| 29 | |
| 30 | /** |
| 31 | * {@link ItemReader} for reading database records built on top of Hibernate. |
| 32 | * |
| 33 | * It executes the HQL {@link #setQueryString(String)} when initialized and |
| 34 | * iterates over the result set as {@link #read()} method is called, returning |
| 35 | * an object corresponding to current row. |
| 36 | * |
| 37 | * Input source can be configured to use either {@link StatelessSession} |
| 38 | * sufficient for simple mappings without the need to cascade to associated |
| 39 | * objects or standard hibernate {@link Session} for more advanced mappings or |
| 40 | * when caching is desired. |
| 41 | * |
| 42 | * When stateful session is used it will be cleared after successful commit |
| 43 | * without being flushed (no inserts or updates are expected). |
| 44 | * |
| 45 | * @author Robert Kasanicky |
| 46 | * @author Dave Syer |
| 47 | */ |
| 48 | public class HibernateCursorItemReader extends ExecutionContextUserSupport implements ItemReader, ItemStream, |
| 49 | InitializingBean { |
| 50 | |
| 51 | private static final String RESTART_DATA_ROW_NUMBER_KEY = "row.number"; |
| 52 | |
| 53 | private SessionFactory sessionFactory; |
| 54 | |
| 55 | private StatelessSession statelessSession; |
| 56 | |
| 57 | private Session statefulSession; |
| 58 | |
| 59 | private ScrollableResults cursor; |
| 60 | |
| 61 | private String queryString; |
| 62 | |
| 63 | private boolean useStatelessSession = true; |
| 64 | |
| 65 | private int lastCommitRowNumber = 0; |
| 66 | |
| 67 | /* Current count of processed records. */ |
| 68 | private int currentProcessedRow = 0; |
| 69 | |
| 70 | private boolean initialized = false; |
| 71 | |
| 72 | private boolean saveState = false; |
| 73 | |
| 74 | public HibernateCursorItemReader() { |
| 75 | setName(ClassUtils.getShortName(HibernateCursorItemReader.class)); |
| 76 | } |
| 77 | |
| 78 | public Object read() { |
| 79 | |
| 80 | if (cursor.next()) { |
| 81 | currentProcessedRow++; |
| 82 | Object[] data = cursor.get(); |
| 83 | if (data.length > 1) { |
| 84 | return data; |
| 85 | } |
| 86 | return data[0]; |
| 87 | } |
| 88 | return null; |
| 89 | } |
| 90 | |
| 91 | /** |
| 92 | * Closes the result set cursor and hibernate session. |
| 93 | */ |
| 94 | public void close(ExecutionContext executionContext) { |
| 95 | initialized = false; |
| 96 | if (cursor != null) { |
| 97 | cursor.close(); |
| 98 | } |
| 99 | currentProcessedRow = 0; |
| 100 | if (useStatelessSession) { |
| 101 | if (statelessSession != null) { |
| 102 | statelessSession.close(); |
| 103 | } |
| 104 | } |
| 105 | else { |
| 106 | if (statefulSession != null) { |
| 107 | statefulSession.close(); |
| 108 | } |
| 109 | } |
| 110 | } |
| 111 | |
| 112 | /** |
| 113 | * Creates cursor for the query. |
| 114 | */ |
| 115 | public void open(ExecutionContext executionContext) { |
| 116 | Assert.state(!initialized, "Cannot open an already opened ItemReader, call close first"); |
| 117 | |
| 118 | if (useStatelessSession) { |
| 119 | statelessSession = sessionFactory.openStatelessSession(); |
| 120 | cursor = statelessSession.createQuery(queryString).scroll(); |
| 121 | } |
| 122 | else { |
| 123 | statefulSession = sessionFactory.openSession(); |
| 124 | cursor = statefulSession.createQuery(queryString).scroll(); |
| 125 | } |
| 126 | initialized = true; |
| 127 | |
| 128 | if (executionContext.containsKey(getKey(RESTART_DATA_ROW_NUMBER_KEY))) { |
| 129 | currentProcessedRow = Integer.parseInt(executionContext.getString(getKey(RESTART_DATA_ROW_NUMBER_KEY))); |
| 130 | cursor.setRowNumber(currentProcessedRow - 1); |
| 131 | } |
| 132 | |
| 133 | } |
| 134 | |
| 135 | /** |
| 136 | * @param sessionFactory hibernate session factory |
| 137 | */ |
| 138 | public void setSessionFactory(SessionFactory sessionFactory) { |
| 139 | this.sessionFactory = sessionFactory; |
| 140 | } |
| 141 | |
| 142 | public void afterPropertiesSet() throws Exception { |
| 143 | Assert.notNull(sessionFactory); |
| 144 | Assert.hasLength(queryString); |
| 145 | } |
| 146 | |
| 147 | /** |
| 148 | * @param queryString HQL query string |
| 149 | */ |
| 150 | public void setQueryString(String queryString) { |
| 151 | this.queryString = queryString; |
| 152 | } |
| 153 | |
| 154 | /** |
| 155 | * Can be set only in uninitialized state. |
| 156 | * |
| 157 | * @param useStatelessSession <code>true</code> to use |
| 158 | * {@link StatelessSession} <code>false</code> to use standard hibernate |
| 159 | * {@link Session} |
| 160 | */ |
| 161 | public void setUseStatelessSession(boolean useStatelessSession) { |
| 162 | Assert.state(!initialized); |
| 163 | this.useStatelessSession = useStatelessSession; |
| 164 | } |
| 165 | |
| 166 | /** |
| 167 | */ |
| 168 | public void update(ExecutionContext executionContext) { |
| 169 | if (saveState) { |
| 170 | Assert.notNull(executionContext, "ExecutionContext must not be null"); |
| 171 | executionContext.putString(getKey(RESTART_DATA_ROW_NUMBER_KEY), "" + currentProcessedRow); |
| 172 | } |
| 173 | } |
| 174 | |
| 175 | /** |
| 176 | * Mark is supported as long as this {@link ItemStream} is used in a |
| 177 | * single-threaded environment. The state backing the mark is a single |
| 178 | * counter, keeping track of the current position, so multiple threads |
| 179 | * cannot be accommodated. |
| 180 | * |
| 181 | * @see org.springframework.batch.item.ItemReader#mark() |
| 182 | */ |
| 183 | public void mark() { |
| 184 | lastCommitRowNumber = currentProcessedRow; |
| 185 | if (!useStatelessSession) { |
| 186 | statefulSession.clear(); |
| 187 | } |
| 188 | } |
| 189 | |
| 190 | /* |
| 191 | * (non-Javadoc) |
| 192 | * |
| 193 | * @see org.springframework.batch.item.stream.ItemStreamAdapter#reset(org.springframework.batch.item.ExecutionContext) |
| 194 | */ |
| 195 | public void reset() { |
| 196 | currentProcessedRow = lastCommitRowNumber; |
| 197 | if (lastCommitRowNumber == 0) { |
| 198 | cursor.beforeFirst(); |
| 199 | } |
| 200 | else { |
| 201 | // Set the cursor so that next time it is advanced it will |
| 202 | // come back to the committed row. |
| 203 | cursor.setRowNumber(lastCommitRowNumber - 1); |
| 204 | } |
| 205 | } |
| 206 | |
| 207 | public void setSaveState(boolean saveState) { |
| 208 | this.saveState = saveState; |
| 209 | } |
| 210 | } |