OsmHandler.java

// This software is released into the Public Domain.  See copying.txt for details.
package org.openstreetmap.osmosis.xml.v0_6.impl;

import java.util.logging.Logger;

import org.openstreetmap.osmosis.core.OsmosisRuntimeException;
import org.openstreetmap.osmosis.core.task.v0_6.Sink;
import org.openstreetmap.osmosis.xml.common.ElementProcessor;
import org.xml.sax.Attributes;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.helpers.DefaultHandler;

/**
 * This class is a SAX default handler for processing OSM XML files. It utilises
 * a tree of element processors to extract the data from the xml structure.
 *
 * @author Brett Henderson
 */
public class OsmHandler extends DefaultHandler {
	private static final Logger LOG = Logger.getLogger(OsmHandler.class.getName());
	private static final String ELEMENT_NAME_OSM = "osm";
	
	/**
	 * The root element processor used to process the osm element.
	 */
	private ElementProcessor osmElementProcessor;
	
	/**
	 * The currently active element processor. This is updated whenever new xml
	 * elements are entered or exited.
	 */
	private ElementProcessor elementProcessor;
	
	
	/**
	 * Provides location information about the current position in the file
	 * which is useful for reporting errors.
	 */
	private Locator documentLocator;
	
	
	/**
	 * Creates a new instance.
	 * 
	 * @param osmSink
	 *            The new osmSink to write data to.
	 * @param enableDateParsing
	 *            If true, dates will be parsed from xml data, else the current
	 *            date will be used thus saving parsing time.
	 */
	public OsmHandler(Sink osmSink, boolean enableDateParsing) {
		osmElementProcessor = new OsmElementProcessor(null, osmSink, enableDateParsing, true);
	}
	
	
	/**
	 * Begins processing of a new element.
	 * 
	 * @param uri
	 *            The uri.
	 * @param localName
	 *            The localName.
	 * @param qName
	 *            The qName.
	 * @param attributes
	 *            The attributes.
	 */
	@Override
	public void startElement(String uri, String localName, String qName, Attributes attributes) {
		// Get the appropriate element processor for the element.
		if (elementProcessor != null) {
			// We already have an active element processor, therefore use the
			// active element processor to retrieve the appropriate child
			// element processor.
			elementProcessor = elementProcessor.getChild(uri, localName, qName);
		} else if (ELEMENT_NAME_OSM.equals(qName)) {
			// There is no active element processor which means we have
			// encountered the root osm element.
			elementProcessor = osmElementProcessor;
		} else {
			// There is no active element processor which means that this is a
			// root element. The root element in this case does not match the
			// expected name.
			throw new OsmosisRuntimeException("This does not appear to be an OSM XML file.");
		}
		
		// Initialise the element processor with the attributes of the new element.
		elementProcessor.begin(attributes);
	}
	
	
	/**
	 * Ends processing of the current element.
	 * 
	 * @param uri
	 *            The uri.
	 * @param localName
	 *            The localName.
	 * @param qName
	 *            The qName.
	 */
	@Override
	public void endElement(String uri, String localName, String qName) {
		// Tell the currently active element processor to complete its processing.
		elementProcessor.end();
		
		// Set the active element processor to the parent of the existing processor.
		elementProcessor = elementProcessor.getParent();
	}

	
	/**
	 * Sets the document locator which is used to report the position in the
	 * file when errors occur.
	 * 
	 * @param documentLocator
	 *            The document locator.
	 */
	@Override
	public void setDocumentLocator(Locator documentLocator) {
		this.documentLocator = documentLocator;
	}
	
	
	/**
	 * Called by the SAX parser when an error occurs. Used by this class to
	 * report the current position in the file.
	 * 
	 * @param e
	 *            The exception that occurred.
	 * @throws SAXException
	 *             if the error reporting throws an exception.
	 */
	@Override
	public void error(SAXParseException e) throws SAXException {
		LOG.severe(
			"Unable to parse xml file.  publicId=(" + documentLocator.getPublicId()
			+ "), systemId=(" + documentLocator.getSystemId()
			+ "), lineNumber=" + documentLocator.getLineNumber()
			+ ", columnNumber=" + documentLocator.getColumnNumber() + ".");
		
		super.error(e);
	}
}