技巧: 使用 StAX 部分解析 XML 文档

import java.io.*;
import javax.xml.stream.*;
import javax.xml.stream.events.XMLEvent;
public class ParseFilteredByEvent {
   public static void main(String[] args)
      throws FileNotFoundException, XMLStreamException {
      // Use  reference implementation
      System.setProperty(
         "javax.xml.stream.XMLInputFactory",
         "com.bea.xml.stream.MXParserFactory");
      // Create the XML input factory
      XMLInputFactory factory = XMLInputFactory.newInstance();
      // Create event reader
      FileReader reader = new FileReader("somefile.xml");
      XMLEventReader eventReader = factory.createXMLEventReader(reader);
      // Create a filtered reader
      XMLEventReader filteredEventReader =
         factory.createFilteredReader(eventReader, new EventFilter() {
         public boolean accept(XMLEvent event) {
            // Exclude PIs
            return (!event.isProcessingInstruction());
         }
      });
      // Main event loop
      while (filteredEventReader.hasNext()) {
         XMLEvent e = filteredEventReader.next();
         System.out.println(e);
      }
   }
}

      // Create stream reader
      XMLStreamReader xmlr =
         xmlif.createXMLStreamReader(new FileReader("somefile.xml"));
      // Create a filtered stream reader
      XMLStreamReader xmlfr = xmlif.createFilteredReader(xmlr, filter);

   // Exclusion path
   private static QName[] exclude = new QName[] { 
      new QName("invoice"), new QName("item")};
   private static StreamFilter filter = new StreamFilter() {
      // Element level
      int depth = -1;
      // Last matching path segment
      int match = -1;
      // Filter result
      boolean process = true;
      // Character position in document
      int currentPos = -1;
      
      public boolean accept(XMLStreamReader reader) {
         // Get character position
         Location loc = reader.getLocation();
         int pos = loc.getCharacterOffset();
         // Inhibit double execution
         if (pos != currentPos) {
            currentPos = pos;
            switch (reader.getEventType()) {
               case XMLStreamConstants.START_ELEMENT :
                  // Increment element depth
                  if (++depth < exclude.length && match == depth - 1) {
                     // Compare path segment with current element
                     if (reader.getName().equals(exclude[depth]))
                        // Equal - set segment pointer
                        match = depth;
                  }
                  // Process all elements not in path
                  process = match < exclude.length - 1;
                  break;
               // End of XML element
               case XMLStreamConstants.END_ELEMENT :
                  // Process all elements not in path
                  process = match < exclude.length - 1;
                  // Decrement element depth
                  if (--depth < match)
                     // Update segment pointer
                     match = depth;
                  break;
            }
         }
         return process;
      }
   };