source: josm/src/org/openstreetmap/josm/io/OsmWriter.java@ 35

package org.openstreetmap.josm.io;

import java.io.IOException;
import java.io.Writer;
import java.util.Collection;
import java.util.LinkedList;
import java.util.List;
import java.util.Map.Entry;

import org.jdom.Document;
import org.jdom.Element;
import org.jdom.output.Format;
import org.jdom.output.XMLOutputter;
import org.openstreetmap.josm.data.osm.DataSet;
import org.openstreetmap.josm.data.osm.Key;
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.Track;
import org.openstreetmap.josm.data.osm.visitor.Visitor;


/**
 * Save the dataset into a stream as osm intern xml format.
 * @author imi
 */
public class OsmWriter implements Visitor {

        /**
         * The output writer to write the xml stream to.
         */
        private final Writer out;
        /**
         * The commands that should be uploaded on the server.
         */
        private DataSet ds;
        /**
         * The counter for new created objects. Starting at -1 and goes down.
         */
        private long newIdCounter = -1;

        /**
         * Set from the visitor functions as result.
         */
        private Element element;
        /**
         * Filled with all generated properties tags.
         */
        private Collection<Element> properties;
        
        public OsmWriter(Writer out, DataSet dataSet) {
                this.out = out;
                ds = dataSet;
        }

        /**
         * Output the data to the stream
         * @throws IOException In case of stream IO errors.
         */
        @SuppressWarnings("unchecked")
        public void output() throws IOException {
                Element root = new Element("osm");
                List<Element> list = root.getChildren();
                properties = new LinkedList<Element>();
                for (OsmPrimitive osm : ds.allPrimitives()) {
                        if (!osm.isDeleted()) {
                                osm.visit(this);
                                list.add(element);
                        }
                }
                list.addAll(properties);
                properties = new LinkedList<Element>();
                Element deleted = new Element("deleted");
                Collection<Element> allDeleted = deleted.getChildren();
                for (OsmPrimitive osm : ds.allPrimitives()) {
                        if (osm.isDeleted()) {
                                osm.visit(this);
                                allDeleted.add(element);
                        }
                }
                allDeleted.addAll(properties);
                if (!allDeleted.isEmpty())
                        list.add(deleted);

                Document d = new Document(root);
                XMLOutputter xmlOut = new XMLOutputter(Format.getPrettyFormat());
                xmlOut.output(d, out);
        }

        /**
         * Create a properties element.
         */
        private Element parseProperty(OsmPrimitive osm, Entry<Key, String> entry) {
                Element e = new Element("property");
                Key key = entry.getKey();
                e.setAttribute("uid", ""+osm.id);
                e.setAttribute("key", key.name);
                e.setAttribute("value", entry.getValue());
                return e;
        }
        
        /**
         * Add the id attribute to the element and the properties to the collection.
         */
        private void addProperties(Element e, OsmPrimitive osm) {
                if (osm.id == 0)
                        osm.id = newIdCounter--;
                e.setAttribute("uid", ""+osm.id);
                if (osm.keys != null)
                        for (Entry<Key, String> entry : osm.keys.entrySet())
                                properties.add(parseProperty(osm, entry));
        }

        /**
         * Create an node element. Add all properties of the node to the properties-list.
         */
        public void visit(Node n) {
                element = new Element("node");
                addProperties(element, n);
                element.setAttribute("lat", ""+n.coor.lat);
                element.setAttribute("lon", ""+n.coor.lon);
        }

        /**
         * Create an line segment element. Add all properties of the node to the properties-list.
         */
        public void visit(LineSegment ls) {
                element = new Element("segment");
                addProperties(element, ls);
                element.setAttribute("from", ""+ls.start.id);
                element.setAttribute("to", ""+ls.end.id);
        }

        /**
         * Create an track element. Add all properties of the node to the properties-list.
         */
        @SuppressWarnings("unchecked")
        public void visit(Track t) {
                Element e = new Element("track");
                addProperties(e, t);
                for (LineSegment ls : t.segments)
                        e.getChildren().add(new Element("segment").setAttribute("uid", ""+ls.id));
        }

        public void visit(Key k) {
                element = new Element("property");
                addProperties(element, k);
        }
}