Added new library display type. Generified populateLibrary and Gateway listAll functionality.

src/main/java/musicplayer/ConfigManager.java

@@ -1,6 +1,9 @@
 package musicplayer;
 
-import java.io.*;
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileWriter;
+import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;

src/main/java/musicplayer/LibraryConfigGUI.java

@@ -3,7 +3,7 @@ package musicplayer;
 import musicplayer.swingmodels.LibraryListModel;
 
 import javax.swing.*;
-import java.awt.BorderLayout;
+import java.awt.*;
 import java.io.File;
 import java.util.List;
 

src/main/java/musicplayer/LibraryUtils.java

@@ -10,7 +10,7 @@ import org.jaudiotagger.audio.exceptions.ReadOnlyFileException;
 import org.jaudiotagger.tag.Tag;
 import org.jaudiotagger.tag.TagException;
 
-import java.io.*;
+import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.List;

src/main/java/musicplayer/PlayerGUI.java

@@ -90,8 +90,8 @@ public class PlayerGUI implements PlayerCallbackInterface, LibraryCallbackInterf
      *
      * @param libraryData Map of albums with a lists of associated songs.
      */
-    private void populateLibrary(Map<Album, List<Song>> libraryData) {
+    private <T> void populateLibrary(Map<T, List<Song>> libraryData) {
-        TreeMap<Album, List<Song>> sortedData = new TreeMap<>(libraryData);
+        TreeMap<T, List<Song>> sortedData = new TreeMap<>(libraryData);
         DefaultTreeModel model = new DefaultTreeModel(new DefaultMutableTreeNode());
         DefaultMutableTreeNode parentNode = (DefaultMutableTreeNode) model.getRoot();
         sortedData.forEach((k, v) -> {
@@ -236,8 +236,9 @@ public class PlayerGUI implements PlayerCallbackInterface, LibraryCallbackInterf
      */
     private Map<String, Runnable> createDisplayVariantMap() {
         Map<String, Runnable> value = new HashMap<>();
-        value.put("Song", () -> Gateway.listAllSongs().ifPresent(this::populateLibrary));
+        value.put("Song", () -> Gateway.listAllT(Song.class).ifPresent(this::populateLibrary));
         value.put("Album/Song", () -> Gateway.listAllSongsGroupedByAlbum().ifPresent(this::populateLibrary));
+        value.put("Artist/Song", () -> Gateway.listAllSongsGroupedByArtist().ifPresent(this::populateLibrary));
 
         return value;
     }

src/main/java/musicplayer/db/Gateway.java

@@ -43,13 +43,15 @@ public class Gateway {
     }
 
     /**
-     * @return List of all songs currently stored in the database.
+     * List all items in the database of a certain type.
+     * @param typeClass Class representing the type of items to find.
+     * @return List of all items in the database of class typeClass.
      */
-    public static Optional<List<Song>> listAllSongs() {
+    public static <T> Optional<List<T>> listAllT(Class<T> typeClass){
         try (Session session = DatabaseManager.getInstance().getSession()) {
             @SuppressWarnings("unchecked")
-            List<Song> songs = session.createCriteria(Song.class).list();
+            List<T> output = session.createCriteria(typeClass).list();
-            return (songs == null || songs.isEmpty()) ? Optional.empty() : Optional.of(songs);
+            return (output == null || output.isEmpty()) ? Optional.empty() : Optional.of(output);
         }
     }
 
@@ -57,12 +59,22 @@ public class Gateway {
      * @return All songs currently in the database, grouped by album.
      */
     public static Optional<Map<Album, List<Song>>> listAllSongsGroupedByAlbum() {
-        Optional<List<Song>> songList = listAllSongs();
+        Optional<List<Song>> songList = listAllT(Song.class);
         return (songList.isPresent()) ?
                 Optional.of(songList.get().stream().collect(Collectors.groupingBy(Song::getAlbum)))
                 : Optional.empty();
     }
 
+    /**
+     * @return All songs currently in the database, grouped by artist.
+     */
+    public static Optional<Map<Artist, List<Song>>> listAllSongsGroupedByArtist() {
+        Optional<List<Song>> songList = listAllT(Song.class);
+        return (songList.isPresent()) ?
+                Optional.of(songList.get().stream().collect(Collectors.groupingBy(Song::getArtist)))
+                : Optional.empty();
+    }
+
     /**
      * Add a new song to the database.
      *

src/main/java/musicplayer/model/ExtractedMetadata.java

@@ -6,7 +6,10 @@ import org.jaudiotagger.tag.Tag;
 import javax.imageio.ImageIO;
 import java.awt.*;
 import java.awt.image.BufferedImage;
-import java.io.*;
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.Optional;

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

@@ -3,7 +3,9 @@ package musicplayer.swingmodels;
 import musicplayer.model.Song;
 
 import javax.swing.table.AbstractTableModel;
-import java.util.*;
+import java.util.Collections;
+import java.util.List;
+import java.util.Optional;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 

src/test/java/musicplayer/db/GatewayTest.java

@@ -16,7 +16,8 @@ import java.io.File;
 import java.util.List;
 import java.util.Map;
 
-import static org.junit.Assert.*;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
 
 public class GatewayTest {
 
@@ -63,6 +64,28 @@ public class GatewayTest {
         assertEquals(testArtist, retrievedArtist);
     }
 
+    @Test
+    public void testListAllSongsGroupedByArtist() throws Exception {
+        Artist artist1 = new Artist("Test 1");
+        Artist artist2 = new Artist("Test 2");
+        Song song1 = new Song("1", "1", "s1", artist1, new Album("a"), "", "");
+        Song song2 = new Song("2", "1", "s2", artist1, new Album("b"), "", "");
+        Song song3 = new Song("1", "1", "t1", artist2, new Album("c"), "", "");
+        session.beginTransaction();
+        session.save(song1);
+        session.save(song2);
+        session.save(song3);
+        session.getTransaction().commit();
+        assertTrue(Gateway.listAllSongsGroupedByArtist().isPresent());
+        Map<Artist, List<Song>> result = Gateway.listAllSongsGroupedByArtist().get();
+        assertTrue(result.size() == 2);
+        assertTrue(result.get(artist1).size() == 2);
+        assertTrue(result.get(artist2).size() == 1);
+        assertTrue(result.get(artist1).contains(song1));
+        assertTrue(result.get(artist1).contains(song2));
+        assertTrue(result.get(artist2).contains(song3));
+    }
+
     @Test
     public void testGetOneArtistEmptyDB() throws Exception {
         assertTrue(!Gateway.getOneArtist("").isPresent());
@@ -78,8 +101,8 @@ public class GatewayTest {
         session.save(song2);
         session.save(song3);
         session.getTransaction().commit();
-        assertTrue(Gateway.listAllSongs().isPresent());
+        assertTrue(Gateway.listAllT(Song.class).isPresent());
-        List<Song> result = Gateway.listAllSongs().get();
+        List<Song> result = Gateway.listAllT(Song.class).get();
         assertTrue(result.size() == 3);
         assertTrue(result.contains(song1));
         assertTrue(result.contains(song2));
@@ -88,7 +111,7 @@ public class GatewayTest {
 
     @Test
     public void testListAllSongsEmptyDB() throws Exception {
-        assertTrue(!Gateway.listAllSongs().isPresent());
+        assertTrue(!Gateway.listAllT(Song.class).isPresent());
     }
 
     @Test