source: josm/src/org/openstreetmap/josm/io/OsmReader.java@ 72

package org.openstreetmap.josm.io;

import java.io.IOException;
import java.io.Reader;
import java.util.HashMap;
import java.util.Map;

import org.openstreetmap.josm.data.coor.LatLon;
import org.openstreetmap.josm.data.osm.DataSet;
import org.openstreetmap.josm.data.osm.LineSegment;
import org.openstreetmap.josm.data.osm.Node;
import org.openstreetmap.josm.data.osm.OsmPrimitive;
import org.openstreetmap.josm.data.osm.Way;
import org.openstreetmap.josm.data.osm.visitor.AddVisitor;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;

import uk.co.wilson.xml.MinML2;

/**
 * Parser for the Osm Api. Read from an input stream and construct a dataset out of it.
 * 
 * @author Imi
 */
public class OsmReader extends MinML2 {

        /**
         * The dataset to add parsed objects to.
         */
        private DataSet ds = new DataSet();

        /**
         * The visitor to use to add the data to the set.
         */
        private AddVisitor adder = new AddVisitor(ds);
        
        /**
         * The current processed primitive.
         */
        private OsmPrimitive current;

        /**
         * All read nodes so far.
         */
        private Map<Long, Node> nodes = new HashMap<Long, Node>();
        /**
         * All read segents so far.
         */
        private Map<Long, LineSegment> lineSegments = new HashMap<Long, LineSegment>();
        
        /**
         * Parse the given input source and return the dataset.
         */
        public static DataSet parseDataSet(Reader source) throws SAXException, IOException {
                OsmReader osm = new OsmReader(source);

                // clear all negative ids (new to this file)
                for (OsmPrimitive o : osm.ds.allPrimitives())
                        if (o.id < 0)
                                o.id = 0;
                
                return osm.ds;
        }

        private OsmReader(Reader source) throws SAXException, IOException {
                parse(source);
        }

        @Override
        public void startElement(String namespaceURI, String localName, String qName, Attributes atts) throws SAXException {
                try {
                        if (qName.equals("osm")) {
                                if (atts == null)
                                        throw new SAXException("Unknown version.");
                                if (!"0.3".equals(atts.getValue("version")))
                                        throw new SAXException("Unknown version: "+atts.getValue("version"));
                        } else if (qName.equals("node")) {
                                Node n = new Node(new LatLon(getDouble(atts, "lat"), getDouble(atts, "lon")));
                                current = n;
                                readCommon(atts);
                                current.id = getLong(atts, "id");
                                nodes.put(n.id, n);
                        } else if (qName.equals("segment")) {
                                current = new LineSegment(
                                                nodes.get(getLong(atts, "from")), 
                                                nodes.get(getLong(atts, "to")));
                                readCommon(atts);
                                lineSegments.put(current.id, (LineSegment)current);
                        } else if (qName.equals("way")) {
                                current = new Way();
                                readCommon(atts);
                        } else if (qName.equals("seg")) {
                                if (current instanceof Way) {
                                        long id = getLong(atts, "id");
                                        LineSegment ls = lineSegments.get(id);
                                        if (ls == null) {
                                                ls = new LineSegment(id); // incomplete line segment
                                                lineSegments.put(id, ls);
                                                adder.visit(ls);
                                        }
                                        ((Way)current).segments.add(ls);
                                }
                        } else if (qName.equals("tag")) {
                                current.put(atts.getValue("k"), atts.getValue("v"));
                        }
                } catch (NumberFormatException x) {
                        throw new SAXException(x.getMessage(), x);
                } catch (NullPointerException x) {
                        throw new SAXException("NullPointerException. Possible some missing tags.", x);
                }
        }

        
        @Override
        public void endElement(String namespaceURI, String localName, String qName) {
                if (qName.equals("node") || qName.equals("segment") || qName.equals("way") || qName.equals("area")) {
                        current.visit(adder);
                }
        }

        /**
         * Read out the common attributes from atts and put them into this.current.
         */
        private void readCommon(Attributes atts) {
                current.id = getLong(atts, "id");
                String action = atts.getValue("action");
                if ("delete".equals(action))
                        current.setDeleted(true);
                else if ("modify".equals(action)) {
                        current.modified = true;
                        current.modifiedProperties = true;
                } else if ("modify/object".equals(action))
                        current.modified = true;
                else if ("modify/property".equals(action))
                        current.modifiedProperties = true;
        }

        private double getDouble(Attributes atts, String value) {
                return Double.parseDouble(atts.getValue(value));
        }
        private long getLong(Attributes atts, String value) {
                return Long.parseLong(atts.getValue(value));
        }
}