generate missing methods in SerializedOfflinePlayer at runtime

src/main/java/com/comphenix/protocol/events/PacketEvent.java

@@ -527,7 +527,7 @@ private void writeObject(ObjectOutputStream output) throws IOException {
 
         // Write the name of the player (or NULL if it's not set)
         Player player = getPlayer();
-        output.writeObject(player != null ? new SerializedOfflinePlayer(player) : null);
+        output.writeObject(player != null ? SerializedOfflinePlayer.init(player) : null);
     }
 
     private void readObject(ObjectInputStream input) throws ClassNotFoundException, IOException {

src/main/java/com/comphenix/protocol/events/SerializedOfflinePlayer.java

@@ -51,8 +51,12 @@
 import java.lang.reflect.Method;
 import java.time.Duration;
 import java.time.Instant;
+import java.util.ArrayList;
 import java.util.Date;
+import java.util.HashSet;
+import java.util.List;
 import java.util.Map;
+import java.util.Set;
 import java.util.UUID;
 import java.util.concurrent.ConcurrentHashMap;
 
@@ -61,7 +65,7 @@
  *
  * @author Kristian
  */
-class SerializedOfflinePlayer implements OfflinePlayer, Serializable {
+abstract class SerializedOfflinePlayer implements OfflinePlayer, Serializable {
 
     /**
      * Generated by Eclipse.
@@ -84,11 +88,33 @@ class SerializedOfflinePlayer implements OfflinePlayer, Serializable {
     private long lastSeen;
 
     private static final Constructor<?> proxyPlayerConstructor = setupProxyPlayerConstructor();
+    private static final Constructor<? extends SerializedOfflinePlayer> CLASS_CONSTRUCTOR = setupClassConstructor();
+
+    /**
+     * Initialize a serializable offline player object from another offline player.
+     * <p>
+     * All other methods cause an exception.
+     *
+     * @param player - another offline player.
+     * @return A serializable offline player object.
+     */
+    public static SerializedOfflinePlayer init(OfflinePlayer player) {
+        try {
+            CLASS_CONSTRUCTOR.setAccessible(true);
+            return CLASS_CONSTRUCTOR.newInstance(player);
+        } catch (IllegalAccessException e) {
+            throw new RuntimeException("Cannot access reflection.", e);
+        } catch (InstantiationException e) {
+            throw new RuntimeException("Cannot instantiate object.", e);
+        } catch (InvocationTargetException e) {
+            throw new RuntimeException("Error in invocation.", e);
+        }
+    }
 
     /**
      * Constructor used by serialization.
      */
-    public SerializedOfflinePlayer() {
+    protected SerializedOfflinePlayer() {
         // Do nothing
     }
 
@@ -97,7 +123,7 @@ public SerializedOfflinePlayer() {
      *
      * @param offline - another player.
      */
-    public SerializedOfflinePlayer(OfflinePlayer offline) {
+    protected SerializedOfflinePlayer(OfflinePlayer offline) {
         this.name = offline.getName();
         this.uuid = offline.getUniqueId();
         this.firstPlayed = offline.getFirstPlayed();
@@ -342,6 +368,47 @@ public Player getProxyPlayer() {
         }
     }
 
+    private static Constructor<? extends SerializedOfflinePlayer> setupClassConstructor() {
+        final Method[] existingMethods = SerializedOfflinePlayer.class.getDeclaredMethods();
+        final Set<String> existingMethodNames = new HashSet<>();
+
+        for (int idx = 0; idx < existingMethods.length; idx++) {
+            existingMethodNames.add(existingMethods[idx].getName());
+        }
+
+        final Method[] offlinePlayerMethods = OfflinePlayer.class.getMethods();
+        final List<String> methodNamesToAdd = new ArrayList<>();
+
+        for (int idx = 0; idx < offlinePlayerMethods.length; idx++) {
+            final String name = offlinePlayerMethods[idx].getName();
+
+            if (!existingMethodNames.contains(name)) {
+                methodNamesToAdd.add(name);
+            }
+        }
+
+        final ElementMatcher.Junction<ByteCodeElement> missingMethods =
+                ElementMatchers.namedOneOf(methodNamesToAdd.toArray(new String[methodNamesToAdd.size()]));
+
+        final InvocationHandlerAdapter throwException = InvocationHandlerAdapter.of((obj, method, args) -> {
+            throw new UnsupportedOperationException(
+                    "The method " + method.getName() + " is not supported.");
+        });
+
+        try {
+            return ByteBuddyFactory.getInstance()
+                    .createSubclass(SerializedOfflinePlayer.class)
+                    .method(missingMethods)
+                    .intercept(throwException)
+                    .make()
+                    .load(ByteBuddyFactory.getInstance().getClassLoader(), ClassLoadingStrategy.Default.INJECTION)
+                    .getLoaded()
+                    .getConstructor(OfflinePlayer.class);
+        } catch (NoSuchMethodException ex) {
+            throw new RuntimeException("Failed to find SerializedOfflinePlayer constructor!", ex);
+        }
+    }
+
     private static Constructor<? extends Player> setupProxyPlayerConstructor() {
         final Method[] offlinePlayerMethods = OfflinePlayer.class.getMethods();
         final String[] methodNames = new String[offlinePlayerMethods.length];

src/test/java/com/comphenix/protocol/events/SerializedOfflinePlayerTest.java

@@ -39,7 +39,7 @@ public void initMocks() {
         when(offlinePlayer.hasPlayedBefore()).thenReturn(playedBefore);
         when(offlinePlayer.isWhitelisted()).thenReturn(whitelisted);
 
-        serializedOfflinePlayer = new SerializedOfflinePlayer(offlinePlayer);
+        serializedOfflinePlayer = SerializedOfflinePlayer.init(offlinePlayer);
     }
 
     @Test