Support reloading to some extent, if you use protocol lib it will kick all your players... (So you probably should just get a PluginManager...)

One day i'll fully patch to work... (If I don't kick the players it ends up that ProtocolLib implodes and nobody can connect.)

src/main/java/us/myles/ViaVersion/ViaVersionPlugin.java

@@ -9,6 +9,7 @@ import lombok.NonNull;
 import org.bukkit.Bukkit;
 import org.bukkit.entity.Player;
 import org.bukkit.plugin.java.JavaPlugin;
+import us.myles.ViaVersion.api.Pair;
 import us.myles.ViaVersion.api.ViaVersion;
 import us.myles.ViaVersion.api.ViaVersionAPI;
 import us.myles.ViaVersion.api.ViaVersionConfig;
@@ -31,6 +32,7 @@ import us.myles.ViaVersion.util.ReflectionUtil;
 import java.io.File;
 import java.lang.reflect.Field;
 import java.lang.reflect.Method;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 import java.util.UUID;
@@ -42,19 +44,36 @@ import java.util.concurrent.TimeUnit;
 public class ViaVersionPlugin extends JavaPlugin implements ViaVersionAPI, ViaVersionConfig {
 
     private final Map<UUID, UserConnection> portedPlayers = new ConcurrentHashMap<>();
+    private List<ChannelFuture> injectedFutures = new ArrayList<>();
+    private List<Pair<Field, Object>> injectedLists = new ArrayList<>();
     private ViaCommandHandler commandHandler;
     private boolean debug = false;
 
     @Override
-    public void onEnable() {
+    public void onLoad() {
         ViaVersion.setInstance(this);
         generateConfig();
         if (System.getProperty("ViaVersion") != null) {
-            getLogger().severe("ViaVersion is already loaded, we don't support reloads. Please reboot if you wish to update.");
-            getLogger().severe("Some features may not work.");
-            return;
+            if (Bukkit.getPluginManager().getPlugin("ProtocolLib") != null) {
+                getLogger().severe("ViaVersion is already loaded, we're going to kick all the players... because otherwise we'll crash because of ProtocolLib.");
+                for (Player player : Bukkit.getOnlinePlayers()) {
+                    player.kickPlayer("Server reload, please rejoin!");
+                }
+
+            } else {
+                getLogger().severe("ViaVersion is already loaded, this should work fine... Otherwise reboot the server!!!");
+
+            }
         }
 
+        getLogger().info("ViaVersion " + getDescription().getVersion() + " is now loaded, injecting.");
+        injectPacketHandler();
+    }
+
+    @Override
+    public void onEnable() {
+        if (isCheckForUpdates())
+            UpdateUtil.sendUpdateMessage(this);
         // Gather version :)
         Bukkit.getScheduler().scheduleSyncDelayedTask(this, new Runnable() {
             @Override
@@ -70,12 +89,6 @@ public class ViaVersionPlugin extends JavaPlugin implements ViaVersionAPI, ViaVe
             }
         });
 
-        getLogger().info("ViaVersion " + getDescription().getVersion() + " is now enabled, injecting.");
-        injectPacketHandler();
-
-
-        if (isCheckForUpdates())
-            UpdateUtil.sendUpdateMessage(this);
 
         Bukkit.getPluginManager().registerEvents(new UpdateListener(this), this);
 
@@ -83,6 +96,12 @@ public class ViaVersionPlugin extends JavaPlugin implements ViaVersionAPI, ViaVe
         getCommand("viaversion").setTabCompleter(commandHandler);
     }
 
+    @Override
+    public void onDisable() {
+        getLogger().info("ViaVersion is disabling, if this is a reload it may not work.");
+        uninject();
+    }
+
     public void gatherProtocolVersion() {
         try {
             Class<?> serverClazz = ReflectionUtil.nms("MinecraftServer");
@@ -185,6 +204,7 @@ public class ViaVersionPlugin extends JavaPlugin implements ViaVersionAPI, ViaVe
                             }
                         }
                     };
+                    injectedLists.add(new Pair<>(field, connection));
                     field.set(connection, wrapper);
                     // Iterate through current list
                     synchronized (wrapper) {
@@ -213,6 +233,7 @@ public class ViaVersionPlugin extends JavaPlugin implements ViaVersionAPI, ViaVe
                 ChannelInitializer newInit = new ViaVersionInitializer(oldInit);
 
                 ReflectionUtil.set(bootstrapAcceptor, "childHandler", newInit);
+                injectedFutures.add(future);
             } catch (NoSuchFieldException e) {
                 // field not found
                 throw new Exception("Unable to find childHandler, blame " + bootstrapAcceptor.getClass().getName());
@@ -223,6 +244,35 @@ public class ViaVersionPlugin extends JavaPlugin implements ViaVersionAPI, ViaVe
         }
     }
 
+    private void uninject() {
+        // TODO: Uninject from players currently online to prevent protocol lib issues.
+        for (ChannelFuture future : injectedFutures) {
+            ChannelHandler bootstrapAcceptor = future.channel().pipeline().first();
+            try {
+                ChannelInitializer<SocketChannel> oldInit = ReflectionUtil.get(bootstrapAcceptor, "childHandler", ChannelInitializer.class);
+                if (oldInit instanceof ViaVersionInitializer) {
+                    ReflectionUtil.set(bootstrapAcceptor, "childHandler", ((ViaVersionInitializer) oldInit).getOriginal());
+                }
+            } catch (Exception e) {
+                System.out.println("Failed to remove injection... reload won't work with connections sorry");
+            }
+        }
+        injectedFutures.clear();
+
+        for (Pair<Field, Object> pair : injectedLists) {
+            try {
+                Object o = pair.getKey().get(pair.getValue());
+                if (o instanceof ListWrapper) {
+                    pair.getKey().set(pair.getValue(), ((ListWrapper) o).getOriginalList());
+                }
+            } catch (IllegalAccessException e) {
+                System.out.println("Failed to remove injection... reload might not work with connections sorry");
+            }
+        }
+
+        injectedLists.clear();
+    }
+
     @Override
     public boolean isPorted(Player player) {
         return isPorted(player.getUniqueId());

src/main/java/us/myles/ViaVersion/handlers/ViaDecodeHandler.java

@@ -56,6 +56,7 @@ public class ViaDecodeHandler extends ByteToMessageDecoder {
                     throw e;
                 }
             }
+
             // call minecraft decoder
             try {
                 list.addAll(PipelineUtil.callDecode(this.minecraftDecoder, ctx, bytebuf));

src/main/java/us/myles/ViaVersion/handlers/ViaVersionInitializer.java

@@ -12,11 +12,11 @@ import java.lang.reflect.Method;
 
 public class ViaVersionInitializer extends ChannelInitializer<SocketChannel> {
 
-    private final ChannelInitializer<SocketChannel> oldInit;
+    private final ChannelInitializer<SocketChannel> original;
     private Method method;
 
     public ViaVersionInitializer(ChannelInitializer<SocketChannel> oldInit) {
-        this.oldInit = oldInit;
+        this.original = oldInit;
         try {
             this.method = ChannelInitializer.class.getDeclaredMethod("initChannel", Channel.class);
             this.method.setAccessible(true);
@@ -25,13 +25,17 @@ public class ViaVersionInitializer extends ChannelInitializer<SocketChannel> {
         }
     }
 
+    public ChannelInitializer<SocketChannel> getOriginal() {
+        return original;
+    }
+
     @Override
     protected void initChannel(SocketChannel socketChannel) throws Exception {
         UserConnection info = new UserConnection(socketChannel);
         // init protocol
         new ProtocolPipeline(info);
         // Add originals
-        this.method.invoke(this.oldInit, socketChannel);
+        this.method.invoke(this.original, socketChannel);
         // Add our transformers
         ViaEncodeHandler encoder = new ViaEncodeHandler(info, (MessageToByteEncoder) socketChannel.pipeline().get("encoder"));
         ViaDecodeHandler decoder = new ViaDecodeHandler(info, (ByteToMessageDecoder) socketChannel.pipeline().get("decoder"));

src/main/java/us/myles/ViaVersion/util/ListWrapper.java

@@ -14,6 +14,10 @@ public abstract class ListWrapper implements List {
 
     public abstract void handleAdd(Object o);
 
+    public List getOriginalList() {
+        return list;
+    }
+
     @Override
     public synchronized int size() {
         return this.list.size();