| 1 | package org.springframework.batch.item.xml; |
| 2 | |
| 3 | import java.io.File; |
| 4 | import java.io.FileOutputStream; |
| 5 | import java.io.IOException; |
| 6 | import java.nio.ByteBuffer; |
| 7 | import java.nio.channels.FileChannel; |
| 8 | import java.util.ArrayList; |
| 9 | import java.util.Arrays; |
| 10 | import java.util.Iterator; |
| 11 | import java.util.List; |
| 12 | import java.util.Map; |
| 13 | |
| 14 | import javax.xml.stream.XMLEventFactory; |
| 15 | import javax.xml.stream.XMLEventWriter; |
| 16 | import javax.xml.stream.XMLOutputFactory; |
| 17 | import javax.xml.stream.XMLStreamException; |
| 18 | |
| 19 | import org.apache.commons.logging.Log; |
| 20 | import org.apache.commons.logging.LogFactory; |
| 21 | import org.springframework.batch.item.ClearFailedException; |
| 22 | import org.springframework.batch.item.ExecutionContext; |
| 23 | import org.springframework.batch.item.FlushFailedException; |
| 24 | import org.springframework.batch.item.ItemStream; |
| 25 | import org.springframework.batch.item.ItemWriter; |
| 26 | import org.springframework.batch.item.util.ExecutionContextUserSupport; |
| 27 | import org.springframework.batch.item.util.FileUtils; |
| 28 | import org.springframework.batch.item.xml.stax.NoStartEndDocumentStreamWriter; |
| 29 | import org.springframework.beans.factory.InitializingBean; |
| 30 | import org.springframework.core.io.Resource; |
| 31 | import org.springframework.dao.DataAccessResourceFailureException; |
| 32 | import org.springframework.util.Assert; |
| 33 | import org.springframework.util.ClassUtils; |
| 34 | import org.springframework.util.CollectionUtils; |
| 35 | |
| 36 | /** |
| 37 | * An implementation of {@link ItemWriter} which uses StAX and |
| 38 | * {@link EventWriterSerializer} for serializing object to XML. |
| 39 | * |
| 40 | * This item writer also provides restart, statistics and transaction features |
| 41 | * by implementing corresponding interfaces. |
| 42 | * |
| 43 | * Output is buffered until {@link #flush()} is called - only then the actual |
| 44 | * writing to file takes place. |
| 45 | * |
| 46 | * The implementation is *not* thread-safe. |
| 47 | * |
| 48 | * @author Peter Zozom |
| 49 | * @author Robert Kasanicky |
| 50 | * |
| 51 | */ |
| 52 | public class StaxEventItemWriter extends ExecutionContextUserSupport implements ItemWriter, ItemStream, |
| 53 | InitializingBean { |
| 54 | |
| 55 | private static final Log log = LogFactory.getLog(StaxEventItemWriter.class); |
| 56 | |
| 57 | // default encoding |
| 58 | private static final String DEFAULT_ENCODING = "UTF-8"; |
| 59 | |
| 60 | // default encoding |
| 61 | private static final String DEFAULT_XML_VERSION = "1.0"; |
| 62 | |
| 63 | // default root tag name |
| 64 | private static final String DEFAULT_ROOT_TAG_NAME = "root"; |
| 65 | |
| 66 | // restart data property name |
| 67 | private static final String RESTART_DATA_NAME = "position"; |
| 68 | |
| 69 | // restart data property name |
| 70 | private static final String WRITE_STATISTICS_NAME = "record.count"; |
| 71 | |
| 72 | // file system resource |
| 73 | private Resource resource; |
| 74 | |
| 75 | // xml serializer |
| 76 | private EventWriterSerializer serializer; |
| 77 | |
| 78 | // encoding to be used while reading from the resource |
| 79 | private String encoding = DEFAULT_ENCODING; |
| 80 | |
| 81 | // XML version |
| 82 | private String version = DEFAULT_XML_VERSION; |
| 83 | |
| 84 | // name of the root tag |
| 85 | private String rootTagName = DEFAULT_ROOT_TAG_NAME; |
| 86 | |
| 87 | // root element attributes |
| 88 | private Map rootElementAttributes = null; |
| 89 | |
| 90 | // TRUE means, that output file will be overwritten if exists - default is |
| 91 | // TRUE |
| 92 | private boolean overwriteOutput = true; |
| 93 | |
| 94 | // file channel |
| 95 | private FileChannel channel; |
| 96 | |
| 97 | // wrapper for XML event writer that swallows StartDocument and EndDocument |
| 98 | // events |
| 99 | private XMLEventWriter eventWriter; |
| 100 | |
| 101 | // XML event writer |
| 102 | private XMLEventWriter delegateEventWriter; |
| 103 | |
| 104 | // byte offset in file channel at last commit point |
| 105 | private long lastCommitPointPosition = 0; |
| 106 | |
| 107 | // processed record count at last commit point |
| 108 | private long lastCommitPointRecordCount = 0; |
| 109 | |
| 110 | // current count of processed records |
| 111 | private long currentRecordCount = 0; |
| 112 | |
| 113 | private boolean saveState = true; |
| 114 | |
| 115 | // holds the list of items for writing before they are actually written on |
| 116 | // #flush() |
| 117 | private List buffer = new ArrayList(); |
| 118 | |
| 119 | private List headers = new ArrayList(); |
| 120 | |
| 121 | public StaxEventItemWriter() { |
| 122 | setName(ClassUtils.getShortName(StaxEventItemWriter.class)); |
| 123 | } |
| 124 | |
| 125 | /** |
| 126 | * Set output file. |
| 127 | * |
| 128 | * @param resource the output file |
| 129 | */ |
| 130 | public void setResource(Resource resource) { |
| 131 | this.resource = resource; |
| 132 | } |
| 133 | |
| 134 | /** |
| 135 | * Set Object to XML serializer. |
| 136 | * |
| 137 | * @param serializer the Object to XML serializer |
| 138 | */ |
| 139 | public void setSerializer(EventWriterSerializer serializer) { |
| 140 | this.serializer = serializer; |
| 141 | } |
| 142 | |
| 143 | /** |
| 144 | * Get used encoding. |
| 145 | * |
| 146 | * @return the encoding used |
| 147 | */ |
| 148 | public String getEncoding() { |
| 149 | return encoding; |
| 150 | } |
| 151 | |
| 152 | /** |
| 153 | * Set encoding to be used for output file. |
| 154 | * |
| 155 | * @param encoding the encoding to be used |
| 156 | */ |
| 157 | public void setEncoding(String encoding) { |
| 158 | this.encoding = encoding; |
| 159 | } |
| 160 | |
| 161 | /** |
| 162 | * Get XML version. |
| 163 | * |
| 164 | * @return the XML version used |
| 165 | */ |
| 166 | public String getVersion() { |
| 167 | return version; |
| 168 | } |
| 169 | |
| 170 | /** |
| 171 | * Set XML version to be used for output XML. |
| 172 | * |
| 173 | * @param version the XML version to be used |
| 174 | */ |
| 175 | public void setVersion(String version) { |
| 176 | this.version = version; |
| 177 | } |
| 178 | |
| 179 | /** |
| 180 | * Get the tag name of the root element. |
| 181 | * |
| 182 | * @return the root element tag name |
| 183 | */ |
| 184 | public String getRootTagName() { |
| 185 | return rootTagName; |
| 186 | } |
| 187 | |
| 188 | /** |
| 189 | * Set the tag name of the root element. If not set, default name is used |
| 190 | * ("root"). |
| 191 | * |
| 192 | * @param rootTagName the tag name to be used for the root element |
| 193 | */ |
| 194 | public void setRootTagName(String rootTagName) { |
| 195 | this.rootTagName = rootTagName; |
| 196 | } |
| 197 | |
| 198 | /** |
| 199 | * Get attributes of the root element. |
| 200 | * |
| 201 | * @return attributes of the root element |
| 202 | */ |
| 203 | public Map getRootElementAttributes() { |
| 204 | return rootElementAttributes; |
| 205 | } |
| 206 | |
| 207 | /** |
| 208 | * Set the root element attributes to be written. |
| 209 | * |
| 210 | * @param rootElementAttributes attributes of the root element |
| 211 | */ |
| 212 | public void setRootElementAttributes(Map rootElementAttributes) { |
| 213 | this.rootElementAttributes = rootElementAttributes; |
| 214 | } |
| 215 | |
| 216 | /** |
| 217 | * Set "overwrite" flag for the output file. Flag is ignored when output |
| 218 | * file processing is restarted. |
| 219 | * |
| 220 | * @param overwriteOutput |
| 221 | */ |
| 222 | public void setOverwriteOutput(boolean overwriteOutput) { |
| 223 | this.overwriteOutput = overwriteOutput; |
| 224 | } |
| 225 | |
| 226 | /** |
| 227 | * Setter for the headers. This list will be marshalled and output before |
| 228 | * any calls to {@link #write(Object)}. |
| 229 | * @param headers |
| 230 | */ |
| 231 | public void setHeaderItems(Object[] headers) { |
| 232 | this.headers = Arrays.asList(headers); |
| 233 | } |
| 234 | |
| 235 | public void setSaveState(boolean saveState) { |
| 236 | this.saveState = saveState; |
| 237 | } |
| 238 | |
| 239 | /** |
| 240 | * @throws Exception |
| 241 | * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet() |
| 242 | */ |
| 243 | public void afterPropertiesSet() throws Exception { |
| 244 | Assert.notNull(serializer); |
| 245 | } |
| 246 | |
| 247 | /** |
| 248 | * Open the output source |
| 249 | * |
| 250 | * @see org.springframework.batch.item.ItemStream#open(ExecutionContext) |
| 251 | */ |
| 252 | public void open(ExecutionContext executionContext) { |
| 253 | |
| 254 | Assert.notNull(resource); |
| 255 | |
| 256 | long startAtPosition = 0; |
| 257 | boolean restarted = false; |
| 258 | |
| 259 | // if restart data is provided, restart from provided offset |
| 260 | // otherwise start from beginning |
| 261 | if (executionContext.containsKey(getKey(RESTART_DATA_NAME))) { |
| 262 | startAtPosition = executionContext.getLong(getKey(RESTART_DATA_NAME)); |
| 263 | restarted = true; |
| 264 | } |
| 265 | |
| 266 | open(startAtPosition, restarted); |
| 267 | |
| 268 | if (startAtPosition == 0) { |
| 269 | for (Iterator iterator = headers.iterator(); iterator.hasNext();) { |
| 270 | Object header = (Object) iterator.next(); |
| 271 | write(header); |
| 272 | } |
| 273 | } |
| 274 | } |
| 275 | |
| 276 | /** |
| 277 | * Helper method for opening output source at given file position |
| 278 | */ |
| 279 | private void open(long position, boolean restarted) { |
| 280 | |
| 281 | File file; |
| 282 | FileOutputStream os = null; |
| 283 | |
| 284 | try { |
| 285 | file = resource.getFile(); |
| 286 | FileUtils.setUpOutputFile(file, restarted, overwriteOutput); |
| 287 | Assert.state(resource.exists(), "Output resource must exist"); |
| 288 | os = new FileOutputStream(file, true); |
| 289 | channel = os.getChannel(); |
| 290 | setPosition(position); |
| 291 | } |
| 292 | catch (IOException ioe) { |
| 293 | throw new DataAccessResourceFailureException("Unable to write to file resource: [" + resource + "]", ioe); |
| 294 | } |
| 295 | |
| 296 | XMLOutputFactory outputFactory = XMLOutputFactory.newInstance(); |
| 297 | |
| 298 | try { |
| 299 | delegateEventWriter = outputFactory.createXMLEventWriter(os, encoding); |
| 300 | eventWriter = new NoStartEndDocumentStreamWriter(delegateEventWriter); |
| 301 | if (!restarted) { |
| 302 | startDocument(delegateEventWriter); |
| 303 | } |
| 304 | } |
| 305 | catch (XMLStreamException xse) { |
| 306 | throw new DataAccessResourceFailureException("Unable to write to file resource: [" + resource + "]", xse); |
| 307 | } |
| 308 | |
| 309 | } |
| 310 | |
| 311 | /** |
| 312 | * Writes simple XML header containing: |
| 313 | * <ul> |
| 314 | * <li>xml declaration - defines encoding and XML version</li> |
| 315 | * <li>opening tag of the root element and its attributes</li> |
| 316 | * </ul> |
| 317 | * If this is not sufficient for you, simply override this method. Encoding, |
| 318 | * version and root tag name can be retrieved with corresponding getters. |
| 319 | * |
| 320 | * @param writer XML event writer |
| 321 | * @throws XMLStreamException |
| 322 | */ |
| 323 | private void startDocument(XMLEventWriter writer) throws XMLStreamException { |
| 324 | |
| 325 | XMLEventFactory factory = XMLEventFactory.newInstance(); |
| 326 | |
| 327 | // write start document |
| 328 | writer.add(factory.createStartDocument(getEncoding(), getVersion())); |
| 329 | |
| 330 | // write root tag |
| 331 | writer.add(factory.createStartElement("", "", getRootTagName())); |
| 332 | |
| 333 | // write root tag attributes |
| 334 | if (!CollectionUtils.isEmpty(getRootElementAttributes())) { |
| 335 | |
| 336 | for (Iterator i = getRootElementAttributes().entrySet().iterator(); i.hasNext();) { |
| 337 | Map.Entry entry = (Map.Entry) i.next(); |
| 338 | writer.add(factory.createAttribute((String) entry.getKey(), (String) entry.getValue())); |
| 339 | } |
| 340 | |
| 341 | } |
| 342 | |
| 343 | } |
| 344 | |
| 345 | /** |
| 346 | * Writes the EndDocument tag manually. |
| 347 | * |
| 348 | * @param writer XML event writer |
| 349 | * @throws XMLStreamException |
| 350 | */ |
| 351 | protected void endDocument(XMLEventWriter writer) throws XMLStreamException { |
| 352 | |
| 353 | // writer.writeEndDocument(); <- this doesn't work after restart |
| 354 | // we need to write end tag of the root element manually |
| 355 | |
| 356 | ByteBuffer bbuf = ByteBuffer.wrap(("</" + getRootTagName() + ">").getBytes()); |
| 357 | try { |
| 358 | channel.write(bbuf); |
| 359 | } |
| 360 | catch (IOException ioe) { |
| 361 | throw new DataAccessResourceFailureException("Unable to close file resource: [" + resource + "]", ioe); |
| 362 | } |
| 363 | } |
| 364 | |
| 365 | /** |
| 366 | * Flush and close the output source. |
| 367 | * |
| 368 | * @see org.springframework.batch.item.ItemStream#close(ExecutionContext) |
| 369 | */ |
| 370 | public void close(ExecutionContext executionContext) { |
| 371 | |
| 372 | // harmless event to close the root tag if there were no items |
| 373 | XMLEventFactory factory = XMLEventFactory.newInstance(); |
| 374 | try { |
| 375 | delegateEventWriter.add(factory.createCharacters("")); |
| 376 | } |
| 377 | catch (XMLStreamException e) { |
| 378 | log.error(e); |
| 379 | } |
| 380 | |
| 381 | flush(); |
| 382 | try { |
| 383 | endDocument(delegateEventWriter); |
| 384 | eventWriter.close(); |
| 385 | channel.close(); |
| 386 | } |
| 387 | catch (XMLStreamException xse) { |
| 388 | throw new DataAccessResourceFailureException("Unable to close file resource: [" + resource + "]", xse); |
| 389 | } |
| 390 | catch (IOException ioe) { |
| 391 | throw new DataAccessResourceFailureException("Unable to close file resource: [" + resource + "]", ioe); |
| 392 | } |
| 393 | } |
| 394 | |
| 395 | /** |
| 396 | * Write the value object to internal buffer. |
| 397 | * |
| 398 | * @param item the value object |
| 399 | * @see #flush() |
| 400 | */ |
| 401 | public void write(Object item) { |
| 402 | |
| 403 | currentRecordCount++; |
| 404 | buffer.add(item); |
| 405 | } |
| 406 | |
| 407 | /** |
| 408 | * Get the restart data. |
| 409 | * |
| 410 | * @see org.springframework.batch.item.ItemStream#update(ExecutionContext) |
| 411 | */ |
| 412 | public void update(ExecutionContext executionContext) { |
| 413 | |
| 414 | if (saveState) { |
| 415 | Assert.notNull(executionContext, "ExecutionContext must not be null"); |
| 416 | executionContext.putLong(getKey(RESTART_DATA_NAME), getPosition()); |
| 417 | executionContext.putLong(getKey(WRITE_STATISTICS_NAME), currentRecordCount); |
| 418 | } |
| 419 | } |
| 420 | |
| 421 | /* |
| 422 | * Get the actual position in file channel. This method flushes any buffered |
| 423 | * data before position is read. |
| 424 | * |
| 425 | * @return byte offset in file channel |
| 426 | */ |
| 427 | private long getPosition() { |
| 428 | |
| 429 | long position; |
| 430 | |
| 431 | try { |
| 432 | eventWriter.flush(); |
| 433 | position = channel.position(); |
| 434 | } |
| 435 | catch (Exception e) { |
| 436 | throw new DataAccessResourceFailureException("Unable to write to file resource: [" + resource + "]", e); |
| 437 | } |
| 438 | |
| 439 | return position; |
| 440 | } |
| 441 | |
| 442 | /** |
| 443 | * Set the file channel position. |
| 444 | * |
| 445 | * @param newPosition new file channel position |
| 446 | */ |
| 447 | private void setPosition(long newPosition) { |
| 448 | |
| 449 | try { |
| 450 | Assert.state(channel.size() >= lastCommitPointPosition, |
| 451 | "Current file size is smaller than size at last commit"); |
| 452 | channel.truncate(newPosition); |
| 453 | channel.position(newPosition); |
| 454 | } |
| 455 | catch (IOException e) { |
| 456 | throw new DataAccessResourceFailureException("Unable to write to file resource: [" + resource + "]", e); |
| 457 | } |
| 458 | |
| 459 | } |
| 460 | |
| 461 | /** |
| 462 | * Writes buffered items to XML stream and marks restore point. |
| 463 | */ |
| 464 | public void flush() throws FlushFailedException { |
| 465 | |
| 466 | for (Iterator iterator = buffer.listIterator(); iterator.hasNext();) { |
| 467 | Object item = iterator.next(); |
| 468 | serializer.serializeObject(eventWriter, item); |
| 469 | } |
| 470 | try { |
| 471 | eventWriter.flush(); |
| 472 | } |
| 473 | catch (XMLStreamException e) { |
| 474 | throw new FlushFailedException("Failed to flush the events", e); |
| 475 | } |
| 476 | buffer.clear(); |
| 477 | |
| 478 | lastCommitPointPosition = getPosition(); |
| 479 | lastCommitPointRecordCount = currentRecordCount; |
| 480 | } |
| 481 | |
| 482 | /** |
| 483 | * Clear the output buffer |
| 484 | */ |
| 485 | public void clear() throws ClearFailedException { |
| 486 | currentRecordCount = lastCommitPointRecordCount; |
| 487 | buffer.clear(); |
| 488 | } |
| 489 | |
| 490 | } |