| 1 | package org.springframework.batch.item.file; |
| 2 | |
| 3 | import java.util.ArrayList; |
| 4 | import java.util.Arrays; |
| 5 | import java.util.Comparator; |
| 6 | import java.util.List; |
| 7 | import java.util.ListIterator; |
| 8 | |
| 9 | import org.apache.commons.logging.Log; |
| 10 | import org.apache.commons.logging.LogFactory; |
| 11 | import org.springframework.batch.item.ExecutionContext; |
| 12 | import org.springframework.batch.item.ItemReader; |
| 13 | import org.springframework.batch.item.ItemStream; |
| 14 | import org.springframework.batch.item.ItemStreamException; |
| 15 | import org.springframework.batch.item.MarkFailedException; |
| 16 | import org.springframework.batch.item.NoWorkFoundException; |
| 17 | import org.springframework.batch.item.ParseException; |
| 18 | import org.springframework.batch.item.ResetFailedException; |
| 19 | import org.springframework.batch.item.UnexpectedInputException; |
| 20 | import org.springframework.batch.item.util.ExecutionContextUserSupport; |
| 21 | import org.springframework.core.io.Resource; |
| 22 | import org.springframework.util.Assert; |
| 23 | import org.springframework.util.ClassUtils; |
| 24 | |
| 25 | /** |
| 26 | * Reads items from multiple resources sequentially - resource list is given by |
| 27 | * {@link #setResources(Resource[])}, the actual reading is delegated to |
| 28 | * {@link #setDelegate(ResourceAwareItemReaderItemStream)}. |
| 29 | * |
| 30 | * Input resources are ordered using {@link #setComparator(Comparator)} to make |
| 31 | * sure resource ordering is preserved between job runs in restart scenario. |
| 32 | * |
| 33 | * Reset (rollback) capability is implemented by item buffering. |
| 34 | * |
| 35 | * |
| 36 | * @author Robert Kasanicky |
| 37 | */ |
| 38 | public class MultiResourceItemReader extends ExecutionContextUserSupport implements ItemReader, ItemStream { |
| 39 | |
| 40 | private static final Log logger = LogFactory.getLog(MultiResourceItemReader.class); |
| 41 | |
| 42 | /** |
| 43 | * Unique object instance that marks resource boundaries in the item buffer |
| 44 | */ |
| 45 | private static final Object END_OF_RESOURCE_MARKER = new Object(); |
| 46 | |
| 47 | private ResourceAwareItemReaderItemStream delegate; |
| 48 | |
| 49 | private Resource[] resources; |
| 50 | |
| 51 | private MultiResourceIndex index = new MultiResourceIndex(); |
| 52 | |
| 53 | private List itemBuffer = new ArrayList(); |
| 54 | |
| 55 | private ListIterator itemBufferIterator = null; |
| 56 | |
| 57 | private boolean shouldReadBuffer = false; |
| 58 | |
| 59 | private boolean saveState = false; |
| 60 | |
| 61 | private Comparator comparator = new Comparator() { |
| 62 | |
| 63 | /** |
| 64 | * Compares resource filenames. |
| 65 | */ |
| 66 | public int compare(Object o1, Object o2) { |
| 67 | Resource r1 = (Resource) o1; |
| 68 | Resource r2 = (Resource) o2; |
| 69 | return r1.getFilename().compareTo(r2.getFilename()); |
| 70 | } |
| 71 | |
| 72 | }; |
| 73 | |
| 74 | private boolean noInput; |
| 75 | |
| 76 | public MultiResourceItemReader() { |
| 77 | setName(ClassUtils.getShortName(MultiResourceItemReader.class)); |
| 78 | } |
| 79 | |
| 80 | /** |
| 81 | * Reads the next item, jumping to next resource if necessary. |
| 82 | */ |
| 83 | public Object read() throws Exception, UnexpectedInputException, NoWorkFoundException, ParseException { |
| 84 | |
| 85 | if (noInput) { |
| 86 | return null; |
| 87 | } |
| 88 | |
| 89 | Object item; |
| 90 | if (shouldReadBuffer) { |
| 91 | item = readBufferedItem(); |
| 92 | } |
| 93 | else { |
| 94 | item = readNextItem(); |
| 95 | } |
| 96 | |
| 97 | index.incrementItemCount(); |
| 98 | |
| 99 | return item; |
| 100 | } |
| 101 | |
| 102 | /** |
| 103 | * Use the delegate to read the next item, jump to next resource if current |
| 104 | * one is exhausted. Items are appended to the buffer. |
| 105 | * @return next item from input |
| 106 | */ |
| 107 | private Object readNextItem() throws Exception { |
| 108 | |
| 109 | Object item = delegate.read(); |
| 110 | |
| 111 | while (item == null) { |
| 112 | |
| 113 | index.incrementResourceCount(); |
| 114 | |
| 115 | if (index.currentResource >= resources.length) { |
| 116 | return null; |
| 117 | } |
| 118 | itemBuffer.add(END_OF_RESOURCE_MARKER); |
| 119 | |
| 120 | delegate.close(new ExecutionContext()); |
| 121 | delegate.setResource(resources[index.currentResource]); |
| 122 | delegate.open(new ExecutionContext()); |
| 123 | |
| 124 | item = delegate.read(); |
| 125 | } |
| 126 | |
| 127 | itemBuffer.add(item); |
| 128 | |
| 129 | return item; |
| 130 | } |
| 131 | |
| 132 | /** |
| 133 | * Read next item from buffer while keeping track of the position within the |
| 134 | * input for possible restart. |
| 135 | * @return next item from buffer |
| 136 | */ |
| 137 | private Object readBufferedItem() { |
| 138 | |
| 139 | Object buffered = itemBufferIterator.next(); |
| 140 | while (buffered == END_OF_RESOURCE_MARKER) { |
| 141 | index.incrementResourceCount(); |
| 142 | buffered = itemBufferIterator.next(); |
| 143 | } |
| 144 | |
| 145 | if (!itemBufferIterator.hasNext()) { |
| 146 | // buffer is exhausted, continue reading from file |
| 147 | shouldReadBuffer = false; |
| 148 | itemBufferIterator = null; |
| 149 | } |
| 150 | return buffered; |
| 151 | } |
| 152 | |
| 153 | /** |
| 154 | * Remove the longer needed items from buffer, mark the index position and |
| 155 | * call mark() on delegate so that it clears its buffers. |
| 156 | */ |
| 157 | public void mark() throws MarkFailedException { |
| 158 | emptyBuffer(); |
| 159 | |
| 160 | index.mark(); |
| 161 | |
| 162 | delegate.mark(); |
| 163 | } |
| 164 | |
| 165 | /** |
| 166 | * Discard the buffered items that have already been read. |
| 167 | */ |
| 168 | private void emptyBuffer() { |
| 169 | if (!shouldReadBuffer) { |
| 170 | itemBuffer.clear(); |
| 171 | itemBufferIterator = null; |
| 172 | } |
| 173 | else { |
| 174 | itemBuffer = itemBuffer.subList(itemBufferIterator.nextIndex(), itemBuffer.size()); |
| 175 | itemBufferIterator = itemBuffer.listIterator(); |
| 176 | } |
| 177 | } |
| 178 | |
| 179 | /** |
| 180 | * Switches to 'read from buffer' state. |
| 181 | * |
| 182 | * @see ItemReader#reset() |
| 183 | */ |
| 184 | public void reset() throws ResetFailedException { |
| 185 | if (!itemBuffer.isEmpty()) { |
| 186 | shouldReadBuffer = true; |
| 187 | itemBufferIterator = itemBuffer.listIterator(); |
| 188 | } |
| 189 | index.reset(); |
| 190 | } |
| 191 | |
| 192 | /** |
| 193 | * Close the {@link #setDelegate(ResourceAwareItemReaderItemStream)} reader |
| 194 | * and reset instance variable values. |
| 195 | */ |
| 196 | public void close(ExecutionContext executionContext) throws ItemStreamException { |
| 197 | noInput = false; |
| 198 | shouldReadBuffer = false; |
| 199 | itemBufferIterator = null; |
| 200 | index = new MultiResourceIndex(); |
| 201 | itemBuffer.clear(); |
| 202 | delegate.close(new ExecutionContext()); |
| 203 | } |
| 204 | |
| 205 | /** |
| 206 | * Figure out which resource to start with in case of restart, open the |
| 207 | * delegate and restore delegate's position in the resource. |
| 208 | */ |
| 209 | public void open(ExecutionContext executionContext) throws ItemStreamException { |
| 210 | |
| 211 | Assert.notNull(resources, "There must be at least one input resource"); |
| 212 | Assert.notNull(delegate, "Delegate must not be null"); |
| 213 | |
| 214 | noInput = false; |
| 215 | if (resources.length == 0) { |
| 216 | logger.warn("No resources to read"); |
| 217 | noInput = true; |
| 218 | return; |
| 219 | } |
| 220 | |
| 221 | Arrays.sort(resources, comparator); |
| 222 | |
| 223 | index.open(executionContext); |
| 224 | |
| 225 | delegate.setResource(resources[index.currentResource]); |
| 226 | |
| 227 | delegate.open(new ExecutionContext()); |
| 228 | |
| 229 | try { |
| 230 | for (int i = 0; i < index.currentItem; i++) { |
| 231 | delegate.read(); |
| 232 | delegate.mark(); |
| 233 | } |
| 234 | } |
| 235 | catch (Exception e) { |
| 236 | throw new ItemStreamException("Could not restore position on restart", e); |
| 237 | } |
| 238 | } |
| 239 | |
| 240 | /** |
| 241 | * Store the current resource index and position in the resource. |
| 242 | */ |
| 243 | public void update(ExecutionContext executionContext) throws ItemStreamException { |
| 244 | if (saveState) { |
| 245 | index.update(executionContext); |
| 246 | } |
| 247 | } |
| 248 | |
| 249 | /** |
| 250 | * @param delegate reads items from single {@link Resource}. |
| 251 | */ |
| 252 | public void setDelegate(ResourceAwareItemReaderItemStream delegate) { |
| 253 | this.delegate = delegate; |
| 254 | } |
| 255 | |
| 256 | /** |
| 257 | * Set the boolean indicating whether or not state should be saved in the |
| 258 | * provided {@link ExecutionContext} during the {@link ItemStream} call to |
| 259 | * update. |
| 260 | * |
| 261 | * @param saveState |
| 262 | */ |
| 263 | public void setSaveState(boolean saveState) { |
| 264 | this.saveState = saveState; |
| 265 | } |
| 266 | |
| 267 | /** |
| 268 | * @param comparator used to order the injected resources, by default |
| 269 | * compares {@link Resource#getFilename()} values. |
| 270 | */ |
| 271 | public void setComparator(Comparator comparator) { |
| 272 | this.comparator = comparator; |
| 273 | } |
| 274 | |
| 275 | /** |
| 276 | * @param resources input resources |
| 277 | */ |
| 278 | public void setResources(Resource[] resources) { |
| 279 | this.resources = resources; |
| 280 | } |
| 281 | |
| 282 | /** |
| 283 | * Facilitates keeping track of the position within multi-resource input. |
| 284 | */ |
| 285 | private class MultiResourceIndex { |
| 286 | |
| 287 | private static final String RESOURCE_KEY = "resourceIndex"; |
| 288 | |
| 289 | private static final String ITEM_KEY = "itemIndex"; |
| 290 | |
| 291 | private int currentResource = 0; |
| 292 | |
| 293 | private int markedResource = 0; |
| 294 | |
| 295 | private long currentItem = 0; |
| 296 | |
| 297 | private long markedItem = 0; |
| 298 | |
| 299 | public void incrementItemCount() { |
| 300 | currentItem++; |
| 301 | } |
| 302 | |
| 303 | public void incrementResourceCount() { |
| 304 | currentResource++; |
| 305 | currentItem = 0; |
| 306 | } |
| 307 | |
| 308 | public void mark() { |
| 309 | markedResource = currentResource; |
| 310 | markedItem = currentItem; |
| 311 | } |
| 312 | |
| 313 | public void reset() { |
| 314 | currentResource = markedResource; |
| 315 | currentItem = markedItem; |
| 316 | } |
| 317 | |
| 318 | public void open(ExecutionContext ctx) { |
| 319 | if (ctx.containsKey(getKey(RESOURCE_KEY))) { |
| 320 | currentResource = Long.valueOf(ctx.getLong(getKey(RESOURCE_KEY))).intValue(); |
| 321 | } |
| 322 | |
| 323 | if (ctx.containsKey(getKey(ITEM_KEY))) { |
| 324 | currentItem = ctx.getLong(getKey(ITEM_KEY)); |
| 325 | } |
| 326 | } |
| 327 | |
| 328 | public void update(ExecutionContext ctx) { |
| 329 | ctx.putLong(getKey(RESOURCE_KEY), index.currentResource); |
| 330 | ctx.putLong(getKey(ITEM_KEY), index.currentItem); |
| 331 | } |
| 332 | } |
| 333 | |
| 334 | } |