source: josm/src/org/openstreetmap/josm/actions/SaveAction.java@ 54

package org.openstreetmap.josm.actions;

import java.awt.event.ActionEvent;
import java.awt.event.InputEvent;
import java.awt.event.KeyEvent;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;

import javax.swing.JFileChooser;
import javax.swing.JOptionPane;
import javax.swing.KeyStroke;
import javax.swing.filechooser.FileFilter;

import org.openstreetmap.josm.Main;
import org.openstreetmap.josm.data.osm.OsmPrimitive;
import org.openstreetmap.josm.io.GpxWriter;
import org.openstreetmap.josm.io.OsmWriter;

/**
 * Export the data  as OSM intern xml file.
 * 
 * TODO: This is very redundant with SaveGpxAction. Merge both actions into one!
 *  
 * @author imi
 */
public class SaveAction extends JosmAction {

        /**
         * Construct the action with "Save" as label.
         */
        public SaveAction() {
                super("Save", "save", "Save the current data.", null, KeyStroke.getAWTKeyStroke(KeyEvent.VK_S, InputEvent.CTRL_DOWN_MASK));
        }
        
        public void actionPerformed(ActionEvent event) {
                if (Main.main.getMapFrame() == null) {
                        JOptionPane.showMessageDialog(Main.main, "No document open so nothing to save.");
                        return;
                }
                if (isDataSetEmpty() && JOptionPane.NO_OPTION == JOptionPane.showConfirmDialog(Main.main, "The document contains no data. Save anyway?", "Empty document", JOptionPane.YES_NO_OPTION))
                        return;

                JFileChooser fc = new JFileChooser(Main.main.currentDirectory);
                for (int i = 0; i < ExtensionFileFilter.filters.length; ++i)
                        fc.addChoosableFileFilter(ExtensionFileFilter.filters[i]);
                fc.setAcceptAllFileFilterUsed(true);
                fc.showSaveDialog(Main.main);
                File file = fc.getSelectedFile();
                if (file == null)
                        return;
                Main.main.currentDirectory = fc.getCurrentDirectory();
                if (file.exists() && JOptionPane.YES_OPTION != 
                                JOptionPane.showConfirmDialog(Main.main, "File exists. Overwrite?", "Overwrite", JOptionPane.YES_NO_OPTION))
                        return;

                try {
                        String fn = file.getPath();
                        if (fn.indexOf('.') == -1) {
                                FileFilter ff = fc.getFileFilter();
                                if (ff instanceof ExtensionFileFilter) {
                                        fn = fn + "." + ((ExtensionFileFilter)ff).defaultExtension;
                                        file = new File(fn);
                                }
                        }
                        FileWriter fileWriter;
                        if (ExtensionFileFilter.filters[ExtensionFileFilter.GPX].acceptName(fn))
                                new GpxWriter(fileWriter = new FileWriter(file), Main.main.ds).output();
                        else if (ExtensionFileFilter.filters[ExtensionFileFilter.OSM].acceptName(fn))
                                new OsmWriter(fileWriter = new FileWriter(file), Main.main.ds).output();
                        else if (ExtensionFileFilter.filters[ExtensionFileFilter.CSV].acceptName(fn)) {
                                JOptionPane.showMessageDialog(Main.main, "CSV output not supported yet.");
                                return;
                        } else {
                                JOptionPane.showMessageDialog(Main.main, "Unknown file extension.");
                                return;
                        }
                        fileWriter.close();
                        Main.main.getMapFrame().mapView.editLayer().cleanData(null, false);
                } catch (IOException e) {
                        e.printStackTrace();
                        JOptionPane.showMessageDialog(Main.main, "An error occoured while saving.\n"+e.getMessage());
                }
        }

        /**
         * Check the data set if it would be empty on save. It is empty, if it contains
         * no objects (after all objects that are created and deleted without beeing 
         * transfered to the server have been removed).
         *  
         * @return <code>true</code>, if a save result in an empty data set.
         */
        private boolean isDataSetEmpty() {
                for (OsmPrimitive osm : Main.main.ds.allPrimitives())
                        if (!osm.isDeleted() || osm.id > 0)
                                return false;
                return true;
        }

}