Small fixes to mod loader

 - Load classpath mods first, use LinkedHashMap to preserve order
 - Use MethodHandles rather than sun.reflect.ConstructorAccessor in ReflectionUtils (Java 9 compatibility)
 - Move Side class out of ModInfo
 - Change RiftLoader.isClient to RiftLoader.getSide()

src/main/java/org/dimdev/rift/listener/DimensionTypeAdder.java

@@ -9,7 +9,7 @@
 
 public interface DimensionTypeAdder {
     static DimensionType newDimensionType(int id, String name, String suffix, Supplier<? extends Dimension> dimensionSupplier) {
-        return ReflectionUtils.makeEnumInstance(DimensionType.class, new Object[]{name.toUpperCase(), -1, id, name, suffix, dimensionSupplier});
+        return ReflectionUtils.makeEnumInstance(DimensionType.class, name.toUpperCase(), -1, id, name, suffix, dimensionSupplier);
     }
 
     Set<? extends DimensionType> getDimensionTypes();

src/main/java/org/dimdev/rift/listener/client/AmbientMusicTypeProvider.java

@@ -8,7 +8,7 @@
 
 public interface AmbientMusicTypeProvider {
     static MusicType newMusicType(String name, SoundEvent sound, int minDelay, int maxDelay) {
-        return ReflectionUtils.makeEnumInstance(MusicType.class, new Object[] {name, -1, sound, minDelay, maxDelay });
+        return ReflectionUtils.makeEnumInstance(MusicType.class, name, -1, sound, minDelay, maxDelay);
     }
 
     MusicType getAmbientMusicType(Minecraft client);

src/main/java/org/dimdev/rift/mixin/hook/MixinNetHandlerPlayServer.java

@@ -40,7 +40,7 @@ private void handleModCustomPayload(CPacketCustomPayload packet, CallbackInfo ci
         Class<? extends Message> messageClass = Message.REGISTRY.getObject(channelName);
         if (messageClass != null) {
             try {
-                Message message = RiftLoader.instance.newInstanceOfClass(messageClass);
+                Message message = RiftLoader.instance.newInstance(messageClass);
                 message.read(data);
                 message.process(new ServerMessageContext(server, player, netManager));
             } catch (ReflectiveOperationException e) {

src/main/java/org/dimdev/rift/mixin/hook/client/MixinNetHandlerPlayClient.java

@@ -58,7 +58,7 @@ private void handleModCustomPayload(SPacketCustomPayload packet, CallbackInfo ci
         Class<? extends Message> messageClass = Message.REGISTRY.getObject(channelName);
         if (messageClass != null) {
             try {
-                Message message = RiftLoader.instance.newInstanceOfClass(messageClass);
+                Message message = RiftLoader.instance.newInstance(messageClass);
                 message.read(data);
                 message.process(new ClientMessageContext(
                         client,

src/main/java/org/dimdev/riftloader/DuplicateModException.java

@@ -0,0 +1,19 @@
+package org.dimdev.riftloader;
+
+public class DuplicateModException extends RuntimeException {
+    private final ModInfo mod1;
+    private final ModInfo mod2;
+
+    public DuplicateModException(ModInfo mod1, ModInfo mod2) {
+        if (!mod1.id.equals(mod2.id)) {
+            throw new IllegalArgumentException();
+        }
+
+        this.mod1 = mod1;
+        this.mod2 = mod2;
+    }
+
+    public String getMessage() {
+        return "Duplicate mod " + mod1.id + ":\r\n - " + mod1.source + "\r\n - " + mod2.source;
+    }
+}

src/main/java/org/dimdev/riftloader/Main.java

@@ -1,12 +1,11 @@
 package org.dimdev.riftloader;
 
 import net.minecraft.launchwrapper.Launch;
+import org.dimdev.utils.ReflectionUtils;
 
 import javax.swing.*;
 import java.io.*;
-import java.lang.reflect.Method;
 import java.net.URL;
-import java.net.URLClassLoader;
 import java.nio.channels.Channels;
 import java.nio.file.Files;
 import java.nio.file.Paths;
@@ -51,10 +50,10 @@ public static void main(String... args) throws Throwable {
                 new FileOutputStream(serverJar).getChannel().transferFrom(Channels.newChannel(url.openStream()), 0, Long.MAX_VALUE);
             }
 
-            addURLToClasspath(serverJar.toURI().toURL());
+            ReflectionUtils.addURLToClasspath(serverJar.toURI().toURL());
 
             for (String url : LIBRARIES) {
-                addURLToClasspath(getOrDownload(new File("libs"), new URL(url)).toURI().toURL());
+                ReflectionUtils.addURLToClasspath(getOrDownload(new File("libs"), new URL(url)).toURI().toURL());
             }
 
             List<String> argsList = new ArrayList<>(Arrays.asList(args).subList(1, args.length));
@@ -80,12 +79,6 @@ private static File getOrDownload(File directory, URL url) throws IOException {
         return target;
     }
 
-    private static void addURLToClasspath(URL url) throws Exception {
-        Method method = URLClassLoader.class.getDeclaredMethod("addURL", URL.class);
-        method.setAccessible(true);
-        method.invoke(ClassLoader.getSystemClassLoader(), url);
-    }
-
     public static void runClientInstaller() {
         try {
             UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());

src/main/java/org/dimdev/riftloader/ModInfo.java

@@ -10,7 +10,7 @@
 public class ModInfo {
     public static Gson GSON = new GsonBuilder()
             .registerTypeAdapter(Listener.class, (JsonSerializer<Listener>) (listener, type, context) -> {
-                if (listener.priority == 0 && listener.sides == Sides.BOTH) {
+                if (listener.priority == 0 && listener.side == Side.BOTH) {
                     return new JsonPrimitive(listener.className);
                 }
 
@@ -25,20 +25,10 @@ public class ModInfo {
             })
             .create();
 
-    public enum Sides {
-        @SerializedName("client") CLIENT,
-        @SerializedName("server") SERVER,
-        @SerializedName("both") BOTH;
-
-        public boolean includes(Sides sides) {
-            return this == BOTH || this == sides;
-        }
-    }
-
     public static class Listener {
         @SerializedName("class") public String className;
         public int priority = 0;
-        @SerializedName("side") public Sides sides = Sides.BOTH;
+        public Side side = Side.BOTH;
 
         public Listener(String className) {
             this.className = className;

src/main/java/org/dimdev/riftloader/RiftLoader.java

@@ -10,17 +10,16 @@
 import org.dimdev.riftloader.listener.Instantiator;
 import org.dimdev.utils.InstanceListMap;
 import org.dimdev.utils.InstanceMap;
+import org.dimdev.utils.ReflectionUtils;
 
 import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.lang.reflect.Constructor;
-import java.lang.reflect.Method;
 import java.net.MalformedURLException;
 import java.net.URISyntaxException;
 import java.net.URL;
-import java.net.URLClassLoader;
 import java.util.*;
 import java.util.jar.JarEntry;
 import java.util.jar.JarFile;
@@ -32,17 +31,23 @@ public class RiftLoader {
 
     public final File modsDir = new File(Launch.minecraftHome, "mods");
     public final File configDir = new File(Launch.minecraftHome, "config");
-    public boolean isClient;
+    private Side side;
+    private boolean loaded;
 
     public AccessTransformer accessTransformer;
-    private Map<String, ModInfo> modInfoMap = new HashMap<>();
+    private Map<String, ModInfo> modInfoMap = new LinkedHashMap<>();
     private List<Class<?>> listenerClasses = new ArrayList<>();
     private InstanceMap listenerInstanceMap = new InstanceMap();
     private InstanceListMap listeners = new InstanceListMap();
     private InstanceListMap customListenerInstances = new InstanceListMap();
 
     public void load(boolean isClient) {
-        this.isClient = isClient;
+        if (loaded) {
+            throw new IllegalStateException("Already loaded");
+        }
+        loaded = true;
+
+        side = isClient ? Side.CLIENT : Side.SERVER;
 
         findMods(modsDir);
         sortMods();
@@ -55,7 +60,40 @@ public void load(boolean isClient) {
      * the 'modsDir' directory (creating it if it doesn't exist) and loads them
      * into the 'modInfoMap'.
      **/
-    public void findMods(File modsDir) {
+    private void findMods(File modsDir) {
+        // Load classpath mods
+        log.info("Searching mods on classpath");
+        try {
+            Enumeration<URL> urls = ClassLoader.getSystemResources("riftmod.json");
+            while (urls.hasMoreElements()) {
+                URL url = urls.nextElement();
+                InputStream in = url.openStream();
+
+                // Convert jar utls to file urls (from JarUrlConnection.parseSpecs)
+                switch (url.getProtocol()) {
+                    case "jar":
+                        String spec = url.getFile();
+
+                        int separator = spec.indexOf("!/");
+                        if (separator == -1) {
+                            throw new MalformedURLException("no !/ found in url spec:" + spec);
+                        }
+
+                        url = new URL(spec.substring(0, separator));
+
+                        loadModFromJson(in, new File(url.toURI()));
+                        break;
+                    case "file":
+                        loadModFromJson(in, new File(url.toURI()).getParentFile());
+                        break;
+                    default:
+                        throw new RuntimeException("Unsupported protocol: " + url);
+                }
+            }
+        } catch (IOException | URISyntaxException e) {
+            throw new RuntimeException(e);
+        }
+
         // Load jar mods
         log.info("Searching for mods in " + modsDir);
         modsDir.mkdirs();
@@ -90,36 +128,6 @@ public void findMods(File modsDir) {
             }
         }
 
-        // Load classpath mods
-        log.info("Searching mods on classpath");
-        try {
-            Enumeration<URL> urls = ClassLoader.getSystemResources("riftmod.json");
-            while (urls.hasMoreElements()) {
-                URL url = urls.nextElement();
-                InputStream in = url.openStream();
-
-                // Convert jar utls to file urls (from JarUrlConnection.parseSpecs)
-                if (url.getProtocol().equals("jar")) {
-                    String spec = url.getFile();
-
-                    int separator = spec.indexOf("!/");
-                    if (separator == -1) {
-                        throw new MalformedURLException("no !/ found in url spec:" + spec);
-                    }
-
-                    url = new URL(spec.substring(0, separator));
-
-                    loadModFromJson(in, new File(url.toURI()));
-                } else if (url.getProtocol().equals("file")) {
-                    loadModFromJson(in, new File(url.toURI()).getParentFile());
-                } else {
-                    throw new RuntimeException("Unsupported protocol: " + url);
-                }
-            }
-        } catch (IOException | URISyntaxException e) {
-            throw new RuntimeException(e);
-        }
-
         log.info("Loaded " + modInfoMap.size() + " mods");
     }
 
@@ -134,7 +142,7 @@ private void loadModFromJson(InputStream in, File source) {
                 log.error("Mod file " + modInfo.source + "'s riftmod.json is missing a 'id' field");
                 return;
             } else if (modInfoMap.containsKey(modInfo.id)) {
-                throw new ModConflictException("Duplicate mod '" + modInfo.id + "': " + modInfoMap.get(modInfo.id).source + ", " + modInfo.source);
+                throw new DuplicateModException(modInfo, modInfoMap.get(modInfo.id));
             }
 
             // Add the mod to the 'id -> mod info' map
@@ -145,11 +153,11 @@ private void loadModFromJson(InputStream in, File source) {
         }
     }
 
-    public void sortMods() {
-        log.debug("Sorting mods"); // TODO
+    private void sortMods() {
+        log.debug("Sorting mods");
     }
 
-    public void initMods() {
+    private void initMods() {
         log.info("Initializing mods");
         // Load all the mod jars
         for (ModInfo modInfo : modInfoMap.values()) {
@@ -164,7 +172,7 @@ public void initMods() {
         for (ModInfo modInfo : modInfoMap.values()) {
             if (modInfo.listeners != null) {
                 for (ModInfo.Listener listener : modInfo.listeners) {
-                    if (listener.sides.includes(isClient ? ModInfo.Sides.CLIENT : ModInfo.Sides.SERVER)) {
+                    if (listener.side.includes(side)) {
                         Class<?> listenerClass;
                         try {
                             listenerClass = Launch.classLoader.findClass(listener.className);
@@ -185,17 +193,11 @@ public void initMods() {
     }
 
     private static void addURLToClasspath(URL url) {
-        try {
-            Method method = URLClassLoader.class.getDeclaredMethod("addURL", URL.class);
-            method.setAccessible(true);
-            method.invoke(ClassLoader.getSystemClassLoader(), url);
-            Launch.classLoader.addURL(url);
-        } catch (ReflectiveOperationException e) {
-            throw new RuntimeException(e);
-        }
+        ReflectionUtils.addURLToClasspath(url);
+        Launch.classLoader.addURL(url);
     }
 
-    public void initAccessTransformer() {
+    private void initAccessTransformer() {
         try {
             AccessTransformationSet transformations = new AccessTransformationSet();
 
@@ -216,14 +218,14 @@ public void initAccessTransformer() {
         }
     }
 
-    public void addMod(ModInfo mod) {
-        modInfoMap.put(mod.id, mod);
-    }
-
     public Collection<ModInfo> getMods() {
         return modInfoMap.values();
     }
 
+    public Side getSide() {
+        return side;
+    }
+
     public <T> List<T> getListeners(Class<T> listenerInterface) {
         List<T> listenerInstances = listeners.get(listenerInterface);
 
@@ -245,7 +247,7 @@ public <T> void loadListeners(Class<T> listenerInterface) {
                 T listenerInstance = listenerInterface.cast(listenerInstanceMap.get(listenerClass));
                 if (listenerInstance == null) {
                     try {
-                        listenerInstance = listenerInterface.cast(newInstanceOfClass(listenerClass));
+                        listenerInstance = listenerInterface.cast(newInstance(listenerClass));
                         listenerInstanceMap.castAndPut(listenerClass, listenerInstance);
                     } catch (ReflectiveOperationException e) {
                         throw new RuntimeException("Failed to create listener instance", e);
@@ -262,16 +264,16 @@ public <T> void loadListeners(Class<T> listenerInterface) {
         }
     }
 
-    public <T> T newInstanceOfClass(Class<T> listenerClass) throws ReflectiveOperationException {
-        for (Constructor<?> constructor : listenerClass.getConstructors()) {
+    public <T> T newInstance(Class<T> clazz) throws ReflectiveOperationException {
+        for (Constructor<?> constructor : clazz.getConstructors()) {
             if (constructor.getParameterCount() == 0) {
-                return listenerClass.cast(constructor.newInstance());
+                return clazz.cast(constructor.newInstance());
             }
         }
 
         // No no-args constructor found, ask mod instantiators to build an instance
         for (Instantiator instantiator : getListeners(Instantiator.class)) {
-            T instance = instantiator.newInstance(listenerClass);
+            T instance = instantiator.newInstance(clazz);
             if (instance != null) {
                 return instance;
             }

src/main/java/org/dimdev/riftloader/Side.java

@@ -0,0 +1,13 @@
+package org.dimdev.riftloader;
+
+import com.google.gson.annotations.SerializedName;
+
+public enum Side {
+    @SerializedName("client") CLIENT,
+    @SerializedName("server") SERVER,
+    @SerializedName("both") BOTH;
+
+    public boolean includes(Side side) {
+        return this == BOTH || this == side;
+    }
+}

src/main/java/org/dimdev/riftloader/listener/Instantiator.java

@@ -13,10 +13,10 @@ public interface Instantiator {
      * Creates an instance of a certain class, or null if the instantiator
      * can't handle it.
      *
-     * @param listenerClass class to instantiate
+     * @param clazz class to instantiate
      * @return an instance of listenerClass, or null to skip this instantiator
      * @throws ReflectiveOperationException if the instantiator can handle this type of class,
      *                                      but an error occured during instantiation
      */
-    <T> T newInstance(Class<T> listenerClass) throws ReflectiveOperationException;
+    <T> T newInstance(Class<T> clazz) throws ReflectiveOperationException;
 }