| 1 | package org.springframework.batch.item.xml.stax; |
| 2 | |
| 3 | import java.util.NoSuchElementException; |
| 4 | |
| 5 | import javax.xml.namespace.QName; |
| 6 | import javax.xml.stream.XMLEventFactory; |
| 7 | import javax.xml.stream.XMLEventReader; |
| 8 | import javax.xml.stream.XMLStreamException; |
| 9 | import javax.xml.stream.events.EndDocument; |
| 10 | import javax.xml.stream.events.EndElement; |
| 11 | import javax.xml.stream.events.StartDocument; |
| 12 | import javax.xml.stream.events.StartElement; |
| 13 | import javax.xml.stream.events.XMLEvent; |
| 14 | |
| 15 | import org.springframework.dao.DataAccessResourceFailureException; |
| 16 | |
| 17 | /** |
| 18 | * Default implementation of {@link FragmentEventReader} |
| 19 | * |
| 20 | * @author Robert Kasanicky |
| 21 | */ |
| 22 | public class DefaultFragmentEventReader extends AbstractEventReaderWrapper implements FragmentEventReader { |
| 23 | |
| 24 | // true when the next event is the StartElement of next fragment |
| 25 | private boolean startFragmentFollows = false; |
| 26 | |
| 27 | // true when the next event is the EndElement of current fragment |
| 28 | private boolean endFragmentFollows = false; |
| 29 | |
| 30 | // true while cursor is inside fragment |
| 31 | private boolean insideFragment = false; |
| 32 | |
| 33 | // true when reader should behave like the cursor was at the end of document |
| 34 | private boolean fakeDocumentEnd = false; |
| 35 | |
| 36 | private StartDocument startDocumentEvent = null; |
| 37 | |
| 38 | private EndDocument endDocumentEvent = null; |
| 39 | |
| 40 | // fragment root name is remembered so that the matching closing element can |
| 41 | // be identified |
| 42 | private QName fragmentRootName = null; |
| 43 | |
| 44 | // counts the occurrences of current fragmentRootName (increased for |
| 45 | // StartElement, decreased for EndElement) |
| 46 | private int matchCounter = 0; |
| 47 | |
| 48 | /** |
| 49 | * Caches the StartDocument event for later use. |
| 50 | * @param wrappedEventReader the original wrapped event reader |
| 51 | */ |
| 52 | public DefaultFragmentEventReader(XMLEventReader wrappedEventReader) { |
| 53 | super(wrappedEventReader); |
| 54 | try { |
| 55 | startDocumentEvent = (StartDocument) wrappedEventReader.peek(); |
| 56 | } |
| 57 | catch (XMLStreamException e) { |
| 58 | throw new DataAccessResourceFailureException("Error reading start document from event reader", e); |
| 59 | } |
| 60 | |
| 61 | endDocumentEvent = XMLEventFactory.newInstance().createEndDocument(); |
| 62 | } |
| 63 | |
| 64 | public void markStartFragment() { |
| 65 | startFragmentFollows = true; |
| 66 | fragmentRootName = null; |
| 67 | } |
| 68 | |
| 69 | public boolean hasNext() { |
| 70 | try { |
| 71 | if (peek() != null) { |
| 72 | return true; |
| 73 | } |
| 74 | } |
| 75 | catch (XMLStreamException e) { |
| 76 | throw new DataAccessResourceFailureException("Error reading XML stream", e); |
| 77 | } |
| 78 | return false; |
| 79 | } |
| 80 | |
| 81 | public Object next() { |
| 82 | try { |
| 83 | return nextEvent(); |
| 84 | } |
| 85 | catch (XMLStreamException e) { |
| 86 | throw new DataAccessResourceFailureException("Error reading XML stream", e); |
| 87 | } |
| 88 | } |
| 89 | |
| 90 | public XMLEvent nextEvent() throws XMLStreamException { |
| 91 | if (fakeDocumentEnd) { |
| 92 | throw new NoSuchElementException(); |
| 93 | } |
| 94 | XMLEvent event = wrappedEventReader.peek(); |
| 95 | XMLEvent proxyEvent = alterEvent(event, false); |
| 96 | checkFragmentEnd(proxyEvent); |
| 97 | if (event == proxyEvent) { |
| 98 | wrappedEventReader.nextEvent(); |
| 99 | } |
| 100 | |
| 101 | return proxyEvent; |
| 102 | } |
| 103 | |
| 104 | /** |
| 105 | * Sets the endFragmentFollows flag to true if next event is the last event |
| 106 | * of the fragment. |
| 107 | * @param event peek() from wrapped event reader |
| 108 | */ |
| 109 | private void checkFragmentEnd(XMLEvent event) { |
| 110 | if (event.isStartElement() && ((StartElement) event).getName().equals(fragmentRootName)) { |
| 111 | matchCounter++; |
| 112 | } |
| 113 | else if (event.isEndElement() && ((EndElement) event).getName().equals(fragmentRootName)) { |
| 114 | matchCounter--; |
| 115 | if (matchCounter == 0) { |
| 116 | endFragmentFollows = true; |
| 117 | } |
| 118 | } |
| 119 | } |
| 120 | |
| 121 | /** |
| 122 | * @param event peek() from wrapped event reader |
| 123 | * @param peek if true do not change the internal state |
| 124 | * @return StartDocument event if peek() points to beginning of fragment |
| 125 | * EndDocument event if cursor is right behind the end of fragment original |
| 126 | * event otherwise |
| 127 | */ |
| 128 | private XMLEvent alterEvent(XMLEvent event, boolean peek) { |
| 129 | if (startFragmentFollows) { |
| 130 | fragmentRootName = ((StartElement) event).getName(); |
| 131 | if (!peek) { |
| 132 | startFragmentFollows = false; |
| 133 | insideFragment = true; |
| 134 | } |
| 135 | return startDocumentEvent; |
| 136 | } |
| 137 | else if (endFragmentFollows) { |
| 138 | if (!peek) { |
| 139 | endFragmentFollows = false; |
| 140 | insideFragment = false; |
| 141 | fakeDocumentEnd = true; |
| 142 | } |
| 143 | return endDocumentEvent; |
| 144 | } |
| 145 | return event; |
| 146 | } |
| 147 | |
| 148 | public XMLEvent peek() throws XMLStreamException { |
| 149 | if (fakeDocumentEnd) { |
| 150 | return null; |
| 151 | } |
| 152 | return alterEvent(wrappedEventReader.peek(), true); |
| 153 | } |
| 154 | |
| 155 | /** |
| 156 | * Finishes reading the fragment in case the fragment was processed without |
| 157 | * being read until the end. |
| 158 | */ |
| 159 | public void markFragmentProcessed() { |
| 160 | if (insideFragment|| startFragmentFollows) { |
| 161 | try { |
| 162 | while (!(nextEvent() instanceof EndDocument)) { |
| 163 | // just read all events until EndDocument |
| 164 | } |
| 165 | } |
| 166 | catch (XMLStreamException e) { |
| 167 | throw new DataAccessResourceFailureException("Error reading XML stream", e); |
| 168 | } |
| 169 | } |
| 170 | fakeDocumentEnd = false; |
| 171 | } |
| 172 | |
| 173 | public void reset() { |
| 174 | insideFragment = false; |
| 175 | startFragmentFollows = false; |
| 176 | endFragmentFollows = false; |
| 177 | fakeDocumentEnd = false; |
| 178 | } |
| 179 | |
| 180 | } |