Added functionality for reading m3u playlists.

src/main/java/musicplayer/PlayerGUI.java

@@ -10,6 +10,8 @@ import musicplayer.db.Gateway;
 import musicplayer.model.Album;
 import musicplayer.model.Song;
 import musicplayer.swingmodels.PlaylistTableModel;
+import musicplayer.util.LibraryUtils;
+import musicplayer.util.PlaylistUtils;
 
 import javax.swing.*;
 import javax.swing.filechooser.FileNameExtensionFilter;
@@ -17,7 +19,10 @@ import javax.swing.tree.DefaultMutableTreeNode;
 import javax.swing.tree.DefaultTreeModel;
 import javax.swing.tree.TreeNode;
 import java.awt.*;
-import java.awt.event.*;
+import java.awt.event.ItemEvent;
+import java.awt.event.MouseAdapter;
+import java.awt.event.MouseEvent;
+import java.awt.event.MouseListener;
 import java.io.File;
 import java.io.IOException;
 import java.nio.file.Path;
@@ -432,19 +437,20 @@ public class PlayerGUI implements PlayerCallbackInterface, LibraryCallbackInterf
         });
         playlistTools.add(menuItem);
 
+        FileNameExtensionFilter m3uExtensionFilter = new FileNameExtensionFilter("m3u playlist", "m3u");
         menuItem = new JMenuItem("Save Playlist");
         menuItem.addActionListener(e -> {
             if(!playlistTableModel.isEmpty()) {
                 JFileChooser fileChooser = new JFileChooser();
                 fileChooser.setDialogType(JFileChooser.SAVE_DIALOG);
                 fileChooser.setSelectedFile(new File("playlist.m3u"));
-                fileChooser.setFileFilter(new FileNameExtensionFilter("m3u playlist", "m3u"));
+                fileChooser.setFileFilter(m3uExtensionFilter);
                 if (fileChooser.showSaveDialog(mainPanel) == JFileChooser.APPROVE_OPTION) {
                     String filename = fileChooser.getSelectedFile().toString();
                     if (!filename.endsWith(".m3u"))
                         filename += ".m3u";
                     try {
-                        playlistTableModel.writePlaylistToFile(new File(filename));
+                        PlaylistUtils.writePlaylistToFile(playlistTableModel.getSongList(), new File(filename));
                     } catch (IOException e1) {
                         JOptionPane.showMessageDialog(null, e1.getMessage() + "\n" + Arrays.toString(e1.getStackTrace()), "Error", JOptionPane.ERROR_MESSAGE);
                     }
@@ -453,6 +459,17 @@ public class PlayerGUI implements PlayerCallbackInterface, LibraryCallbackInterf
         });
         playlistTools.add(menuItem);
 
+        menuItem = new JMenuItem("Open Playlist");
+        menuItem.addActionListener(e -> {
+            JFileChooser fileChooser = new JFileChooser();
+            fileChooser.setDialogType(JFileChooser.OPEN_DIALOG);
+            fileChooser.setFileFilter(m3uExtensionFilter);
+            if(fileChooser.showOpenDialog(mainPanel) == JFileChooser.APPROVE_OPTION){
+                PlaylistUtils.readPlaylistFromFile(fileChooser.getSelectedFile()).stream().forEach(playlistTableModel::addSong);
+            }
+        });
+        playlistTools.add(menuItem);
+
         // Add everything to the menu bar itself
         menuBar.add(playlistTools);
         return menuBar;

src/main/java/musicplayer/swingmodels/PlaylistTableModel.java

@@ -3,7 +3,6 @@ package musicplayer.swingmodels;
 import musicplayer.model.Song;
 
 import javax.swing.table.AbstractTableModel;
-import java.io.*;
 import java.util.Collections;
 import java.util.List;
 import java.util.Optional;
@@ -170,20 +169,10 @@ public class PlaylistTableModel extends AbstractTableModel {
         fireTableDataChanged();
     }
 
-    public String getM3UPlaylist(){
+    /**
-        StringBuilder output = new StringBuilder("#EXTM3U\n");
+     * @return Songs currently in the playlist.
-        songList.forEach(x -> output.append(x.getM3UFormatString()));
+     */
-        return output.toString();
+    public List<Song> getSongList(){
-    }
+        return songList;
-
-    public void writePlaylistToFile(File targetFile) throws IOException {
-        if(!targetFile.exists())
-            targetFile.createNewFile();
-        try (BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(targetFile), "utf-8"))) {
-            writer.write("#EXTM3U\n");
-            for(Song song : songList){
-               writer.write(song.getM3UFormatString());
-            }
-        }
     }
 }

src/main/java/musicplayer/util/LibraryUtils.java

@@ -1,4 +1,4 @@
-package musicplayer;
+package musicplayer.util;
 
 import musicplayer.callbacks.LibraryCallbackInterface;
 import musicplayer.db.Gateway;
@@ -16,7 +16,7 @@ import java.nio.file.Path;
 import java.util.List;
 import java.util.Optional;
 
-final class LibraryUtils {
+public final class LibraryUtils {
 
     private static final String musicFileExtensionRegex = "(?iu).*\\.(mp3|mp4|flac|ogg)";
     private static Thread updaterThread;
@@ -35,7 +35,7 @@ final class LibraryUtils {
                             .filter(f -> f.toString().matches(musicFileExtensionRegex)).map(LibraryUtils::autoParse)
                             .forEach(x -> x.ifPresent(i -> {
                                 Gateway.addSong(i);
-                                if(callbacksEnabled)
+                                if (callbacksEnabled)
                                     callbackInterface.currentlyUpdating(i.toString());
                             }));
                 } catch (IOException e) {
@@ -63,7 +63,7 @@ final class LibraryUtils {
      * @param targetFile Path to file to extract metadata from.
      * @return Metadata contained in targetFile.
      */
-    private static Optional<ExtractedMetadata> autoParse(Path targetFile) {
+    public static Optional<ExtractedMetadata> autoParse(Path targetFile) {
         Tag audioTags = null;
         try {
             audioTags = AudioFileIO.read(targetFile.toFile()).getTag();

src/main/java/musicplayer/util/PlaylistUtils.java

@@ -0,0 +1,61 @@
+package musicplayer.util;
+
+import musicplayer.model.Album;
+import musicplayer.model.Artist;
+import musicplayer.model.Song;
+
+import java.io.*;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+import java.util.stream.Collectors;
+
+public final class PlaylistUtils {
+
+    /**
+     * Write a list of songs to a file as an m3u format playlist file.
+     * @param playlist Playlist of songs to write.
+     * @param targetFile File to write playlist into.
+     * @throws IOException
+     */
+    public static void writePlaylistToFile(List<Song> playlist, File targetFile) throws IOException {
+        if(!targetFile.exists())
+            targetFile.createNewFile();
+        try (BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(targetFile), "utf-8"))) {
+            writer.write("#EXTM3U\n");
+            for(Song song : playlist){
+                writer.write(song.getM3UFormatString());
+            }
+        }
+    }
+
+    /**
+     * Read songs in from an m3u playlist.
+     * Songs in the playlist with files that don't actually exists will be dropped.
+     * @param targetFile File to read m3u playlist data from.
+     * @return List of songs contained in the playlist.
+     */
+    public static List<Song> readPlaylistFromFile(File targetFile){
+        List<Song> result = new ArrayList<>();
+        if(targetFile.exists()){
+            try {
+                List<String> playlistData = Files.lines(targetFile.toPath()).filter(x -> !x.isEmpty() && !x.contains("#EXTINF")).collect(Collectors.toList());
+                if(playlistData.get(0).equals("#EXTM3U")){
+                    playlistData.remove(0);
+                    List<Path> songPaths = playlistData.stream().map(Paths::get).collect(Collectors.toList());
+                    for(int i = 0; i < songPaths.size(); i++){
+                        if(!Files.exists(songPaths.get(i))){ // If song file doesn't exists, try treating it as relative
+                            songPaths.set(i, Paths.get(targetFile.getParent(), songPaths.get(i).toString()));
+                        }
+                    }
+                    songPaths.stream().map(LibraryUtils::autoParse).filter(Optional::isPresent).map(Optional::get)
+                            .forEach(x -> result.add(new Song(x.getTrackNumber(), x.getDiscNumber(), x.getTitle(), new Artist(x.getArtist()), new Album(x.getAlbum()), x.getGenre(), x.getSongFile())));
+                }
+            } catch (IOException ignored) { }
+        }
+        return result;
+    }
+}