| 1 | package org.springframework.batch.item.support; |
| 2 | |
| 3 | import java.util.ArrayList; |
| 4 | import java.util.List; |
| 5 | import java.util.ListIterator; |
| 6 | |
| 7 | import org.springframework.batch.item.ExecutionContext; |
| 8 | import org.springframework.batch.item.ItemReader; |
| 9 | import org.springframework.batch.item.ItemStream; |
| 10 | import org.springframework.batch.item.ItemStreamException; |
| 11 | import org.springframework.batch.item.MarkFailedException; |
| 12 | import org.springframework.batch.item.NoWorkFoundException; |
| 13 | import org.springframework.batch.item.ParseException; |
| 14 | import org.springframework.batch.item.ResetFailedException; |
| 15 | import org.springframework.batch.item.UnexpectedInputException; |
| 16 | import org.springframework.batch.item.util.ExecutionContextUserSupport; |
| 17 | import org.springframework.util.Assert; |
| 18 | |
| 19 | /** |
| 20 | * Abstract superclass for {@link ItemReader}s which use item buffering to |
| 21 | * support reset/rollback. Supports restart by storing item count in the |
| 22 | * {@link ExecutionContext} (therefore requires item ordering to be preserved |
| 23 | * between runs). |
| 24 | * |
| 25 | * Subclasses are inherently *not* thread-safe. |
| 26 | * |
| 27 | * @author Robert Kasanicky |
| 28 | */ |
| 29 | public abstract class AbstractBufferedItemReaderItemStream implements ItemReader, ItemStream { |
| 30 | |
| 31 | private static final String READ_COUNT = "read.count"; |
| 32 | |
| 33 | private int currentItemCount = 0; |
| 34 | |
| 35 | private int lastMarkedItemCount = 0; |
| 36 | |
| 37 | private boolean shouldReadBuffer = false; |
| 38 | |
| 39 | private List itemBuffer = new ArrayList(); |
| 40 | |
| 41 | private ListIterator itemBufferIterator = null; |
| 42 | |
| 43 | private int lastMarkedBufferIndex = 0; |
| 44 | |
| 45 | private ExecutionContextUserSupport ecSupport = new ExecutionContextUserSupport(); |
| 46 | |
| 47 | private boolean saveState = true; |
| 48 | |
| 49 | /** |
| 50 | * Read next item from input. |
| 51 | * @return item |
| 52 | * @throws Exception |
| 53 | */ |
| 54 | protected abstract Object doRead() throws Exception; |
| 55 | |
| 56 | /** |
| 57 | * Open resources necessary to start reading input. |
| 58 | */ |
| 59 | protected abstract void doOpen() throws Exception; |
| 60 | |
| 61 | /** |
| 62 | * Close the resources opened in {@link #doOpen()}. |
| 63 | */ |
| 64 | protected abstract void doClose() throws Exception; |
| 65 | |
| 66 | /** |
| 67 | * Move to the given item index. Subclasses should override this method if |
| 68 | * there is a more efficient way of moving to given index than re-reading |
| 69 | * the input using {@link #doRead()}. |
| 70 | */ |
| 71 | protected void jumpToItem(int itemIndex) throws Exception { |
| 72 | for (int i = 0; i < itemIndex; i++) { |
| 73 | doRead(); |
| 74 | } |
| 75 | } |
| 76 | |
| 77 | public Object read() throws Exception, UnexpectedInputException, NoWorkFoundException, ParseException { |
| 78 | |
| 79 | currentItemCount++; |
| 80 | |
| 81 | if (shouldReadBuffer) { |
| 82 | if (itemBufferIterator.hasNext()) { |
| 83 | return itemBufferIterator.next(); |
| 84 | } |
| 85 | else { |
| 86 | // buffer is exhausted, continue reading from file |
| 87 | shouldReadBuffer = false; |
| 88 | itemBufferIterator = null; |
| 89 | } |
| 90 | } |
| 91 | |
| 92 | Object item = doRead(); |
| 93 | itemBuffer.add(item); |
| 94 | |
| 95 | return item; |
| 96 | } |
| 97 | |
| 98 | /** |
| 99 | * Mark is supported as long as this {@link ItemStream} is used in a |
| 100 | * single-threaded environment. The state backing the mark is a single |
| 101 | * counter, keeping track of the current position, so multiple threads |
| 102 | * cannot be accommodated. |
| 103 | * |
| 104 | * @see org.springframework.batch.item.support.AbstractItemReader#mark() |
| 105 | */ |
| 106 | public void mark() throws MarkFailedException { |
| 107 | |
| 108 | if (!shouldReadBuffer) { |
| 109 | itemBuffer.clear(); |
| 110 | itemBufferIterator = null; |
| 111 | lastMarkedBufferIndex = 0; |
| 112 | } |
| 113 | else { |
| 114 | lastMarkedBufferIndex = itemBufferIterator.nextIndex(); |
| 115 | } |
| 116 | |
| 117 | lastMarkedItemCount = currentItemCount; |
| 118 | } |
| 119 | |
| 120 | public void reset() throws ResetFailedException { |
| 121 | |
| 122 | currentItemCount = lastMarkedItemCount; |
| 123 | shouldReadBuffer = true; |
| 124 | itemBufferIterator = itemBuffer.listIterator(lastMarkedBufferIndex); |
| 125 | } |
| 126 | |
| 127 | protected int getCurrentItemCount() { |
| 128 | return currentItemCount; |
| 129 | } |
| 130 | |
| 131 | protected void setCurrentItemCount(int count) { |
| 132 | this.currentItemCount = count; |
| 133 | } |
| 134 | |
| 135 | public void close(ExecutionContext executionContext) throws ItemStreamException { |
| 136 | currentItemCount = 0; |
| 137 | lastMarkedItemCount = 0; |
| 138 | lastMarkedBufferIndex = 0; |
| 139 | itemBufferIterator = null; |
| 140 | shouldReadBuffer = false; |
| 141 | itemBuffer.clear(); |
| 142 | |
| 143 | try { |
| 144 | doClose(); |
| 145 | } |
| 146 | catch (Exception e) { |
| 147 | throw new ItemStreamException("Error while closing item reader", e); |
| 148 | } |
| 149 | } |
| 150 | |
| 151 | public void open(ExecutionContext executionContext) throws ItemStreamException { |
| 152 | |
| 153 | try { |
| 154 | doOpen(); |
| 155 | } |
| 156 | catch (Exception e) { |
| 157 | throw new ItemStreamException("Failed to initialize the reader", e); |
| 158 | } |
| 159 | |
| 160 | if (executionContext.containsKey(ecSupport.getKey(READ_COUNT))) { |
| 161 | int itemCount = new Long(executionContext.getLong(ecSupport.getKey(READ_COUNT))).intValue(); |
| 162 | |
| 163 | try { |
| 164 | jumpToItem(itemCount); |
| 165 | } |
| 166 | catch (Exception e) { |
| 167 | throw new ItemStreamException("Could not move to stored position on restart", e); |
| 168 | } |
| 169 | |
| 170 | currentItemCount = itemCount; |
| 171 | } |
| 172 | |
| 173 | } |
| 174 | |
| 175 | public void update(ExecutionContext executionContext) throws ItemStreamException { |
| 176 | if (saveState) { |
| 177 | Assert.notNull(executionContext, "ExecutionContext must not be null"); |
| 178 | executionContext.putLong(ecSupport.getKey(READ_COUNT), currentItemCount); |
| 179 | } |
| 180 | |
| 181 | } |
| 182 | |
| 183 | public void setName(String name) { |
| 184 | ecSupport.setName(name); |
| 185 | } |
| 186 | |
| 187 | /** |
| 188 | * Set the flag that determines whether to save internal data for |
| 189 | * {@link ExecutionContext}. Only switch this to false if you don't want to |
| 190 | * save any state from this stream, and you don't need it to be restartable. |
| 191 | * |
| 192 | * @param saveState flag value (default true). |
| 193 | */ |
| 194 | public void setSaveState(boolean saveState) { |
| 195 | this.saveState = saveState; |
| 196 | } |
| 197 | |
| 198 | } |