| 1 | package org.springframework.batch.item.xml; |
| 2 | |
| 3 | import java.io.InputStream; |
| 4 | |
| 5 | import javax.xml.namespace.QName; |
| 6 | import javax.xml.stream.XMLEventReader; |
| 7 | import javax.xml.stream.XMLInputFactory; |
| 8 | import javax.xml.stream.XMLStreamException; |
| 9 | import javax.xml.stream.events.StartElement; |
| 10 | |
| 11 | import org.apache.commons.logging.Log; |
| 12 | import org.apache.commons.logging.LogFactory; |
| 13 | import org.springframework.batch.item.file.ResourceAwareItemReaderItemStream; |
| 14 | import org.springframework.batch.item.support.AbstractBufferedItemReaderItemStream; |
| 15 | import org.springframework.batch.item.xml.stax.DefaultFragmentEventReader; |
| 16 | import org.springframework.batch.item.xml.stax.FragmentEventReader; |
| 17 | import org.springframework.beans.factory.InitializingBean; |
| 18 | import org.springframework.core.io.Resource; |
| 19 | import org.springframework.dao.DataAccessResourceFailureException; |
| 20 | import org.springframework.util.Assert; |
| 21 | import org.springframework.util.ClassUtils; |
| 22 | |
| 23 | /** |
| 24 | * Item reader for reading XML input based on StAX. |
| 25 | * |
| 26 | * It extracts fragments from the input XML document which correspond to records |
| 27 | * for processing. The fragments are wrapped with StartDocument and EndDocument |
| 28 | * events so that the fragments can be further processed like standalone XML |
| 29 | * documents. |
| 30 | * |
| 31 | * The implementation is *not* thread-safe. |
| 32 | * |
| 33 | * @author Robert Kasanicky |
| 34 | */ |
| 35 | public class StaxEventItemReader extends AbstractBufferedItemReaderItemStream implements |
| 36 | ResourceAwareItemReaderItemStream, InitializingBean { |
| 37 | |
| 38 | private static final Log logger = LogFactory.getLog(StaxEventItemReader.class); |
| 39 | |
| 40 | private FragmentEventReader fragmentReader; |
| 41 | |
| 42 | private XMLEventReader eventReader; |
| 43 | |
| 44 | private EventReaderDeserializer eventReaderDeserializer; |
| 45 | |
| 46 | private Resource resource; |
| 47 | |
| 48 | private InputStream inputStream; |
| 49 | |
| 50 | private String fragmentRootElementName; |
| 51 | |
| 52 | private boolean noInput; |
| 53 | |
| 54 | public StaxEventItemReader() { |
| 55 | setName(ClassUtils.getShortName(StaxEventItemReader.class)); |
| 56 | } |
| 57 | |
| 58 | public void setResource(Resource resource) { |
| 59 | this.resource = resource; |
| 60 | } |
| 61 | |
| 62 | /** |
| 63 | * @param eventReaderDeserializer maps xml fragments corresponding to |
| 64 | * records to objects |
| 65 | */ |
| 66 | public void setFragmentDeserializer(EventReaderDeserializer eventReaderDeserializer) { |
| 67 | this.eventReaderDeserializer = eventReaderDeserializer; |
| 68 | } |
| 69 | |
| 70 | /** |
| 71 | * @param fragmentRootElementName name of the root element of the fragment |
| 72 | * TODO String can be ambiguous due to namespaces, use QName? |
| 73 | */ |
| 74 | public void setFragmentRootElementName(String fragmentRootElementName) { |
| 75 | this.fragmentRootElementName = fragmentRootElementName; |
| 76 | } |
| 77 | |
| 78 | /** |
| 79 | * Ensure that all required dependencies for the ItemReader to run are |
| 80 | * provided after all properties have been set. |
| 81 | * |
| 82 | * @see org.springframework.beans.factory.InitializingBean#afterPropertiesSet() |
| 83 | * @throws IllegalArgumentException if the Resource, FragmentDeserializer or |
| 84 | * FragmentRootElementName is null, or if the root element is empty. |
| 85 | * @throws IllegalStateException if the Resource does not exist. |
| 86 | */ |
| 87 | public void afterPropertiesSet() throws Exception { |
| 88 | Assert.notNull(eventReaderDeserializer, "The FragmentDeserializer must not be null."); |
| 89 | Assert.hasLength(fragmentRootElementName, "The FragmentRootElementName must not be null"); |
| 90 | } |
| 91 | |
| 92 | /** |
| 93 | * Responsible for moving the cursor before the StartElement of the fragment |
| 94 | * root. |
| 95 | * |
| 96 | * This implementation simply looks for the next corresponding element, it |
| 97 | * does not care about element nesting. You will need to override this |
| 98 | * method to correctly handle composite fragments. |
| 99 | * |
| 100 | * @return <code>true</code> if next fragment was found, |
| 101 | * <code>false</code> otherwise. |
| 102 | */ |
| 103 | protected boolean moveCursorToNextFragment(XMLEventReader reader) { |
| 104 | try { |
| 105 | while (true) { |
| 106 | while (reader.peek() != null && !reader.peek().isStartElement()) { |
| 107 | reader.nextEvent(); |
| 108 | } |
| 109 | if (reader.peek() == null) { |
| 110 | return false; |
| 111 | } |
| 112 | QName startElementName = ((StartElement) reader.peek()).getName(); |
| 113 | if (startElementName.getLocalPart().equals(fragmentRootElementName)) { |
| 114 | return true; |
| 115 | } |
| 116 | else { |
| 117 | reader.nextEvent(); |
| 118 | } |
| 119 | } |
| 120 | } |
| 121 | catch (XMLStreamException e) { |
| 122 | throw new DataAccessResourceFailureException("Error while reading from event reader", e); |
| 123 | } |
| 124 | } |
| 125 | |
| 126 | protected void doClose() throws Exception { |
| 127 | try { |
| 128 | if (fragmentReader != null) { |
| 129 | fragmentReader.close(); |
| 130 | } |
| 131 | if (inputStream != null) { |
| 132 | inputStream.close(); |
| 133 | } |
| 134 | } |
| 135 | finally { |
| 136 | fragmentReader = null; |
| 137 | inputStream = null; |
| 138 | } |
| 139 | |
| 140 | } |
| 141 | |
| 142 | protected void doOpen() throws Exception { |
| 143 | Assert.notNull(resource, "The Resource must not be null."); |
| 144 | |
| 145 | noInput = false; |
| 146 | if (!resource.exists()) { |
| 147 | noInput = true; |
| 148 | logger.warn("Input resource does not exist"); |
| 149 | return; |
| 150 | } |
| 151 | |
| 152 | inputStream = resource.getInputStream(); |
| 153 | eventReader = XMLInputFactory.newInstance().createXMLEventReader(inputStream); |
| 154 | fragmentReader = new DefaultFragmentEventReader(eventReader); |
| 155 | |
| 156 | } |
| 157 | |
| 158 | /** |
| 159 | * Move to next fragment and map it to item. |
| 160 | */ |
| 161 | protected Object doRead() throws Exception { |
| 162 | if (noInput) { |
| 163 | return null; |
| 164 | } |
| 165 | |
| 166 | Object item = null; |
| 167 | |
| 168 | if (moveCursorToNextFragment(fragmentReader)) { |
| 169 | fragmentReader.markStartFragment(); |
| 170 | item = eventReaderDeserializer.deserializeFragment(fragmentReader); |
| 171 | fragmentReader.markFragmentProcessed(); |
| 172 | } |
| 173 | |
| 174 | return item; |
| 175 | } |
| 176 | |
| 177 | } |