Add lazy group implementation and creator.

diff --git a/src/main/java/net/pterodactylus/demoscenemusic/data/DataManager.java b/src/main/java/net/pterodactylus/demoscenemusic/data/DataManager.java
index b56634f..374bb6c 100644 (file)
--- a/src/main/java/net/pterodactylus/demoscenemusic/data/DataManager.java
+++ b/src/main/java/net/pterodactylus/demoscenemusic/data/DataManager.java
@@ -49,6 +49,7 @@ import net.pterodactylus.util.database.ValueFieldWhereClause;
 public class DataManager {
 
        private final ObjectCreator<Artist> artistCreator = new ArtistCreator();
+       private final ObjectCreator<Group> groupCreator = new GroupCreator();
 
        private final Database database;
 
@@ -250,4 +251,45 @@ public class DataManager {
 
        }
 
+       private class LazyGroup extends DefaultGroup {
+
+               private final Memoizer<Void> artistsMemoizer = new Memoizer<Void>(new Callable<Void>() {
+
+                       @Override
+                       public Void call() throws Exception {
+                               if (!hasValue("artists")) {
+                                       value("artists", Collection.class).set(getArtistsByGroup(id()));
+                               }
+                               return null;
+                       }
+
+               });
+
+               public LazyGroup(String id) {
+                       super(id);
+               }
+
+               /**
+                * {@inheritDoc}
+                */
+               @Override
+               public Collection<Artist> artists() {
+                       artistsMemoizer.get();
+                       return super.artists();
+               }
+
+       }
+
+       private class GroupCreator implements ObjectCreator<Group> {
+
+               /**
+                * {@inheritDoc}
+                */
+               @Override
+               public Group createObject(ResultSet resultSet) throws SQLException {
+                       return new LazyGroup(resultSet.getString("GROUPS.ID")).name(resultSet.getString("GROUPS.NAME")).url(resultSet.getString("GROUPS.URL"));
+               }
+
+       }
+
 }