| 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 | |
| 17 | package org.springframework.batch.core.step.item; |
| 18 | |
| 19 | import java.util.List; |
| 20 | |
| 21 | import org.springframework.batch.core.StepContribution; |
| 22 | import org.springframework.batch.core.StepListener; |
| 23 | import org.springframework.batch.core.listener.MulticasterBatchListener; |
| 24 | import org.springframework.batch.item.ItemProcessor; |
| 25 | import org.springframework.batch.item.ItemWriter; |
| 26 | import org.springframework.beans.factory.InitializingBean; |
| 27 | import org.springframework.util.Assert; |
| 28 | |
| 29 | /** |
| 30 | * Simple implementation of the {@link ChunkProcessor} interface that handles |
| 31 | * basic item writing and processing. Any exceptions encountered will be |
| 32 | * rethrown. |
| 33 | * |
| 34 | * @see ChunkOrientedTasklet |
| 35 | */ |
| 36 | public class SimpleChunkProcessor<I, O> implements ChunkProcessor<I>, InitializingBean { |
| 37 | |
| 38 | private ItemProcessor<? super I, ? extends O> itemProcessor; |
| 39 | |
| 40 | private ItemWriter<? super O> itemWriter; |
| 41 | |
| 42 | private final MulticasterBatchListener<I, O> listener = new MulticasterBatchListener<I, O>(); |
| 43 | |
| 44 | /** |
| 45 | * Default constructor for ease of configuration (both itemWriter and |
| 46 | * itemProcessor are mandatory). |
| 47 | */ |
| 48 | @SuppressWarnings("unused") |
| 49 | private SimpleChunkProcessor() { |
| 50 | this(null, null); |
| 51 | } |
| 52 | |
| 53 | public SimpleChunkProcessor(ItemProcessor<? super I, ? extends O> itemProcessor, ItemWriter<? super O> itemWriter) { |
| 54 | this.itemProcessor = itemProcessor; |
| 55 | this.itemWriter = itemWriter; |
| 56 | } |
| 57 | |
| 58 | /** |
| 59 | * @param itemProcessor the {@link ItemProcessor} to set |
| 60 | */ |
| 61 | public void setItemProcessor(ItemProcessor<? super I, ? extends O> itemProcessor) { |
| 62 | this.itemProcessor = itemProcessor; |
| 63 | } |
| 64 | |
| 65 | /** |
| 66 | * @param itemWriter the {@link ItemWriter} to set |
| 67 | */ |
| 68 | public void setItemWriter(ItemWriter<? super O> itemWriter) { |
| 69 | this.itemWriter = itemWriter; |
| 70 | } |
| 71 | |
| 72 | /** |
| 73 | * Check mandatory properties. |
| 74 | * |
| 75 | * @see InitializingBean#afterPropertiesSet() |
| 76 | */ |
| 77 | public void afterPropertiesSet() throws Exception { |
| 78 | Assert.notNull(itemWriter, "ItemWriter must be set"); |
| 79 | Assert.notNull(itemProcessor, "ItemProcessor must be set"); |
| 80 | } |
| 81 | |
| 82 | /** |
| 83 | * Register some {@link StepListener}s with the handler. Each will get the |
| 84 | * callbacks in the order specified at the correct stage. |
| 85 | * |
| 86 | * @param listeners |
| 87 | */ |
| 88 | public void setListeners(List<? extends StepListener> listeners) { |
| 89 | for (StepListener listener : listeners) { |
| 90 | registerListener(listener); |
| 91 | } |
| 92 | } |
| 93 | |
| 94 | /** |
| 95 | * Register a listener for callbacks at the appropriate stages in a process. |
| 96 | * |
| 97 | * @param listener a {@link StepListener} |
| 98 | */ |
| 99 | public void registerListener(StepListener listener) { |
| 100 | this.listener.register(listener); |
| 101 | } |
| 102 | |
| 103 | /** |
| 104 | * @return the listener |
| 105 | */ |
| 106 | protected MulticasterBatchListener<I, O> getListener() { |
| 107 | return listener; |
| 108 | } |
| 109 | |
| 110 | /** |
| 111 | * @param item the input item |
| 112 | * @return the result of the processing |
| 113 | * @throws Exception |
| 114 | */ |
| 115 | protected final O doProcess(I item) throws Exception { |
| 116 | |
| 117 | if (itemProcessor == null) { |
| 118 | @SuppressWarnings("unchecked") |
| 119 | O result = (O) item; |
| 120 | return result; |
| 121 | } |
| 122 | |
| 123 | try { |
| 124 | listener.beforeProcess(item); |
| 125 | O result = itemProcessor.process(item); |
| 126 | listener.afterProcess(item, result); |
| 127 | return result; |
| 128 | } |
| 129 | catch (Exception e) { |
| 130 | listener.onProcessError(item, e); |
| 131 | throw e; |
| 132 | } |
| 133 | |
| 134 | } |
| 135 | |
| 136 | /** |
| 137 | * Surrounds the actual write call with listener callbacks. |
| 138 | * |
| 139 | * @param items |
| 140 | * @throws Exception |
| 141 | */ |
| 142 | protected final void doWrite(List<O> items) throws Exception { |
| 143 | |
| 144 | if (itemWriter == null) { |
| 145 | return; |
| 146 | } |
| 147 | |
| 148 | try { |
| 149 | listener.beforeWrite(items); |
| 150 | writeItems(items); |
| 151 | doAfterWrite(items); |
| 152 | } |
| 153 | catch (Exception e) { |
| 154 | doOnWriteError(e, items); |
| 155 | throw e; |
| 156 | } |
| 157 | |
| 158 | } |
| 159 | |
| 160 | /** |
| 161 | * Call the listener's after write method. |
| 162 | * |
| 163 | * @param items |
| 164 | */ |
| 165 | protected final void doAfterWrite(List<O> items) { |
| 166 | listener.afterWrite(items); |
| 167 | } |
| 168 | protected final void doOnWriteError(Exception e, List<O> items) { |
| 169 | listener.onWriteError(e, items); |
| 170 | } |
| 171 | |
| 172 | protected void writeItems(List<O> items) throws Exception { |
| 173 | if (itemWriter != null) { |
| 174 | itemWriter.write(items); |
| 175 | } |
| 176 | } |
| 177 | |
| 178 | public final void process(StepContribution contribution, Chunk<I> inputs) throws Exception { |
| 179 | |
| 180 | // Allow temporary state to be stored in the user data field |
| 181 | initializeUserData(inputs); |
| 182 | |
| 183 | // If there is no input we don't have to do anything more |
| 184 | if (isComplete(inputs)) { |
| 185 | return; |
| 186 | } |
| 187 | |
| 188 | // Make the transformation, calling remove() on the inputs iterator if |
| 189 | // any items are filtered. Might throw exception and cause rollback. |
| 190 | Chunk<O> outputs = transform(contribution, inputs); |
| 191 | |
| 192 | // Adjust the filter count based on available data |
| 193 | contribution.incrementFilterCount(getFilterCount(inputs, outputs)); |
| 194 | |
| 195 | // Adjust the outputs if necessary for housekeeping purposes, and then |
| 196 | // write them out... |
| 197 | write(contribution, inputs, getAdjustedOutputs(inputs, outputs)); |
| 198 | |
| 199 | } |
| 200 | |
| 201 | /** |
| 202 | * Extension point for subclasses to allow them to memorise the contents of |
| 203 | * the inputs, in case they are needed for accounting purposes later. The |
| 204 | * default implementation sets up some user data to remember the original |
| 205 | * size of the inputs. If this method is overridden then some or all of |
| 206 | * {@link #isComplete(Chunk)}, {@link #getFilterCount(Chunk, Chunk)} and |
| 207 | * {@link #getAdjustedOutputs(Chunk, Chunk)} might also need to be, to |
| 208 | * ensure that the user data is handled consistently. |
| 209 | * |
| 210 | * @param inputs the inputs for the process |
| 211 | */ |
| 212 | protected void initializeUserData(Chunk<I> inputs) { |
| 213 | inputs.setUserData(inputs.size()); |
| 214 | } |
| 215 | |
| 216 | /** |
| 217 | * Extension point for subclasses to calculate the filter count. Defaults to |
| 218 | * the difference between input size and output size. |
| 219 | * |
| 220 | * @param inputs the inputs after transformation |
| 221 | * @param outputs the outputs after transformation |
| 222 | * |
| 223 | * @return the difference in sizes |
| 224 | * |
| 225 | * @see #initializeUserData(Chunk) |
| 226 | */ |
| 227 | protected int getFilterCount(Chunk<I> inputs, Chunk<O> outputs) { |
| 228 | return (Integer) inputs.getUserData() - outputs.size(); |
| 229 | } |
| 230 | |
| 231 | /** |
| 232 | * Extension point for subclasses that want to store additional data in the |
| 233 | * inputs. Default just checks if inputs are empty. |
| 234 | * |
| 235 | * @param inputs the input chunk |
| 236 | * @return true if it is empty |
| 237 | * |
| 238 | * @see #initializeUserData(Chunk) |
| 239 | */ |
| 240 | protected boolean isComplete(Chunk<I> inputs) { |
| 241 | return inputs.isEmpty(); |
| 242 | } |
| 243 | |
| 244 | /** |
| 245 | * Extension point for subclasses that want to adjust the outputs based on |
| 246 | * additional saved data in the inputs. Default implementation just returns |
| 247 | * the outputs unchanged. |
| 248 | * |
| 249 | * @param inputs the inputs for the transformation |
| 250 | * @param outputs the result of the transformation |
| 251 | * @return the outputs unchanged |
| 252 | * |
| 253 | * @see #initializeUserData(Chunk) |
| 254 | */ |
| 255 | protected Chunk<O> getAdjustedOutputs(Chunk<I> inputs, Chunk<O> outputs) { |
| 256 | return outputs; |
| 257 | } |
| 258 | |
| 259 | /** |
| 260 | * Simple implementation delegates to the {@link #doWrite(List)} method and |
| 261 | * increments the write count in the contribution. Subclasses can handle |
| 262 | * more complicated scenarios, e.g.with fault tolerance. If output items are |
| 263 | * skipped they should be removed from the inputs as well. |
| 264 | * |
| 265 | * @param contribution the current step contribution |
| 266 | * @param inputs the inputs that gave rise to the ouputs |
| 267 | * @param outputs the outputs to write |
| 268 | * @throws Exception if there is a problem |
| 269 | */ |
| 270 | protected void write(StepContribution contribution, Chunk<I> inputs, Chunk<O> outputs) throws Exception { |
| 271 | try { |
| 272 | doWrite(outputs.getItems()); |
| 273 | } |
| 274 | catch (Exception e) { |
| 275 | /* |
| 276 | * For a simple chunk processor (no fault tolerance) we are done |
| 277 | * here, so prevent any more processing of these inputs. |
| 278 | */ |
| 279 | inputs.clear(); |
| 280 | throw e; |
| 281 | } |
| 282 | contribution.incrementWriteCount(outputs.size()); |
| 283 | } |
| 284 | |
| 285 | protected Chunk<O> transform(StepContribution contribution, Chunk<I> inputs) throws Exception { |
| 286 | Chunk<O> outputs = new Chunk<O>(); |
| 287 | for (Chunk<I>.ChunkIterator iterator = inputs.iterator(); iterator.hasNext();) { |
| 288 | final I item = iterator.next(); |
| 289 | O output; |
| 290 | try { |
| 291 | output = doProcess(item); |
| 292 | } |
| 293 | catch (Exception e) { |
| 294 | /* |
| 295 | * For a simple chunk processor (no fault tolerance) we are done |
| 296 | * here, so prevent any more processing of these inputs. |
| 297 | */ |
| 298 | inputs.clear(); |
| 299 | throw e; |
| 300 | } |
| 301 | if (output != null) { |
| 302 | outputs.add(output); |
| 303 | } |
| 304 | else { |
| 305 | iterator.remove(); |
| 306 | } |
| 307 | } |
| 308 | return outputs; |
| 309 | } |
| 310 | |
| 311 | } |