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