Cache player names gotten from Mojang API

.gitignore

@@ -114,3 +114,6 @@ run/
 
 # Minecraft server for testing
 testserver/
+
+# Player Name Caches
+cachedPlayerNames.json

src/main/java/com/technicjelle/bluemapofflineplayermarkers/BlueMapOfflinePlayerMarkers.java

@@ -41,6 +41,7 @@ public void onEnable() {
 		config = new PaperConfig(this);
 
 		Singletons.init(new PaperServer(this), getLogger(), config, new BlueMapMarkerHandler(), new BMApiStatus());
+		Singletons.getServer().startUp();
 
 		//all actual startup and shutdown logic moved to BlueMapAPI enable/disable methods, so `/bluemap reload` also reloads this plugin
 		BlueMapAPI.onEnable(onEnableListener);
@@ -74,6 +75,7 @@ public void onEnable() {
 	public void onDisable() {
 		BlueMapAPI.unregisterListener(onEnableListener);
 		BlueMapAPI.unregisterListener(onDisableListener);
+		Singletons.getServer().shutDown();
 		Singletons.getLogger().info("BlueMap Offline Player Markers plugin disabled!");
 		Singletons.cleanup();
 	}

src/main/java/com/technicjelle/bluemapofflineplayermarkers/common/Server.java

@@ -1,22 +1,62 @@
 package com.technicjelle.bluemapofflineplayermarkers.common;
 
 import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
 import com.google.gson.JsonObject;
+import com.google.gson.reflect.TypeToken;
+import com.technicjelle.bluemapofflineplayermarkers.core.Singletons;
 
-import java.io.IOException;
-import java.io.InputStreamReader;
+import java.io.*;
 import java.net.URL;
 import java.net.URLConnection;
 import java.nio.file.Path;
 import java.time.Instant;
+import java.util.HashMap;
+import java.util.Map;
 import java.util.Optional;
 import java.util.UUID;
 
 public interface Server {
-	Gson _gson = new Gson();
+	Gson _gson = new GsonBuilder()
+			.setLenient()
+//			.setPrettyPrinting() //Disabled to discourage people from editing the file by hand
+			.enableComplexMapKeySerialization()
+			.create();
+
+	Map<UUID, String> _cachedPlayerNames = new HashMap<>();
+	String _cacheFileName = "cachedPlayerNames.json";
+
+	default void startUp() {
+		//load cached player names
+		Path cacheFolder = Singletons.getServer().getConfigFolder();
+		File cacheFile = new File(cacheFolder.toFile(), _cacheFileName);
+		if (cacheFile.exists()) {
+			try (InputStreamReader reader = new FileReader(cacheFile)) {
+				Map<UUID, String> map = _gson.fromJson(reader, new TypeToken<Map<UUID, String>>() {}.getType());
+				if (map != null) {
+					_cachedPlayerNames.putAll(map);
+				}
+			} catch (IOException e) {
+				throw new RuntimeException(e);
+			}
+		}
+	}
+
+	default void shutDown() {
+		//save cached player names
+		Path cacheFolder = Singletons.getServer().getConfigFolder();
+		File cacheFile = new File(cacheFolder.toFile(), _cacheFileName);
+		try (Writer writer = new FileWriter(cacheFile)) {
+			_gson.toJson(_cachedPlayerNames, writer);
+		} catch (IOException e) {
+			throw new RuntimeException(e);
+		}
+	}
 
 	boolean isPlayerOnline(UUID playerUUID);
 
+	Path getConfigFolder();
+
 	Path getPlayerDataFolder();
 
 	/**
@@ -29,15 +69,24 @@ public interface Server {
 
 	/**
 	 * Requests the player's name from the Mojang API. May be slow.
+	 *
 	 * @throws IOException If there was an error with the connection.
 	 */
 	static String nameFromMojangAPI(UUID playerUUID) throws IOException {
+		String name = _cachedPlayerNames.get(playerUUID);
+		if (name != null) {
+			Singletons.getLogger().info("Requested player name from Mojang API, but returning from cache instead for " + playerUUID);
+			return name;
+		}
+		Singletons.getLogger().info("Requesting player name from Mojang API for " + playerUUID);
 		URL url = new URL("https://sessionserver.mojang.com/session/minecraft/profile/" + playerUUID);
 		URLConnection request = url.openConnection();
 		request.connect();
 
 		JsonObject response = _gson.fromJson(new InputStreamReader(request.getInputStream()), JsonObject.class);
-		return response.get("name").getAsString();
+		name = response.get("name").getAsString();
+		_cachedPlayerNames.put(playerUUID, name);
+		return name;
 	}
 
 	Optional<UUID> guessWorldUUID(Object object);

src/main/java/com/technicjelle/bluemapofflineplayermarkers/impl/paper/PaperServer.java

@@ -2,6 +2,7 @@
 
 import com.destroystokyo.paper.profile.PlayerProfile;
 import com.technicjelle.bluemapofflineplayermarkers.common.Server;
+import com.technicjelle.bluemapofflineplayermarkers.core.Singletons;
 import org.bukkit.Bukkit;
 import org.bukkit.OfflinePlayer;
 import org.bukkit.World;
@@ -15,9 +16,11 @@
 import java.util.UUID;
 
 public class PaperServer implements Server {
+	final JavaPlugin plugin;
 	final org.bukkit.Server server;
 
 	public PaperServer(JavaPlugin plugin) {
+		this.plugin = plugin;
 		this.server = plugin.getServer();
 	}
 
@@ -27,6 +30,11 @@ public boolean isPlayerOnline(UUID playerUUID) {
 		return op.isOnline();
 	}
 
+	@Override
+	public Path getConfigFolder() {
+		return plugin.getDataFolder().toPath();
+	}
+
 	@Override
 	public Path getPlayerDataFolder() {
 		//I really don't like "getWorlds().get(0)" as a way to get the main world, but as far as I can tell there is no other way

src/test/java/LoadOfflineMarkersTest.java

@@ -7,6 +7,7 @@
 public class LoadOfflineMarkersTest {
 	@After
 	public void cleanup() {
+		Singletons.getServer().shutDown();
 		Singletons.cleanup();
 	}
 
@@ -19,6 +20,7 @@ public void extract_info_from_playerdata_files() {
 				new MockMarkerHandler(),
 				new MockBMApiStatus()
 		);
+		Singletons.getServer().startUp();
 		FileMarkerLoader.loadOfflineMarkers();
 	}
 }

src/test/java/mockery/MockServer.java

@@ -22,6 +22,11 @@ public boolean isPlayerOnline(UUID playerUUID) {
 		return false;
 	}
 
+	@Override
+	public Path getConfigFolder() {
+		return getPlayerDataFolder();
+	}
+
 	@Override
 	public Path getPlayerDataFolder() {
 		Path path = Paths.get("").resolve("src/test/resources/" + playerDataFolderName);