Upgrade plugin loader

Author: rcx

src/main/java/the/bytecode/club/jda/JDA.java

@@ -16,8 +16,6 @@
 import java.io.FileInputStream;
 import java.io.IOException;
 import java.net.MalformedURLException;
-import java.net.URL;
-import java.net.URLClassLoader;
 import java.nio.file.Files;
 import java.nio.file.Paths;
 import java.util.ArrayList;
@@ -90,14 +88,7 @@ else if (!pluginsDir.isDirectory())
                 System.out.println("Skipping non-jar " + pluginFile.getName());
                 continue;
             }
-
-            try {
-                ClassLoader loader = URLClassLoader.newInstance(new URL[] {pluginFile.toURL()}, JDA.class.getClassLoader());
-                Class.forName("Plugin", true, loader).getConstructor().newInstance();
-            } catch (ReflectiveOperationException e) {
-                System.err.println("Failed to load plugin " + pluginFile.getName());
-                e.printStackTrace();
-            }
+            PluginLoader.tryLoadPlugin(pluginFile);
         }
     }
 

src/main/java/the/bytecode/club/jda/PluginLoader.java

@@ -0,0 +1,63 @@
+package the.bytecode.club.jda;
+
+import java.io.*;
+import java.lang.reflect.Method;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.net.URLClassLoader;
+
+public class PluginLoader {
+    public static void tryLoadPlugin(File pluginFile) throws MalformedURLException {
+        String pluginFileName = pluginFile.getName();
+        try {
+            ClassLoader loader = new URLClassLoader(new URL[] { pluginFile.toURI().toURL() }) {
+                public URL getResource(String name) {
+                    if (name.startsWith("\0JDA-hack:"))
+                        return findResource(name.substring(name.indexOf(':') + 1));
+                    else
+                        return super.getResource(name);
+                }
+            };
+
+            InputStream metaInfStream = loader.getResourceAsStream("\0JDA-hack:META-INF/MANIFEST.MF");
+            if (metaInfStream == null) {
+                System.out.println("Invalid plugin " + pluginFileName + ": no manifest");
+                return;
+            }
+
+            String mainClass = parseManifest(metaInfStream);
+            if (mainClass == null) {
+                System.out.println("Invalid plugin " + pluginFileName + ": unable to parse manifest");
+                return;
+            }
+
+            Class<?> clazz = Class.forName(mainClass, true, loader);
+            Method mainMethod = clazz.getMethod("main", String[].class);
+            mainMethod.invoke(null, (Object) new String[0]);
+        } catch (ReflectiveOperationException e) {
+            System.err.println("Failed to load plugin " + pluginFileName);
+            e.printStackTrace();
+        }
+    }
+
+    // Read Main-Class attribute from manifest. Return null if invalid
+    public static String parseManifest(InputStream manifestStream) {
+        BufferedReader reader = new BufferedReader(new InputStreamReader(manifestStream));
+        String line;
+        try {
+            while ((line = reader.readLine()) != null) {
+                String[] parts = line.split(":");
+                if (parts.length < 2)
+                    return null;
+
+                String header = parts[0];
+                if (header.equals("Main-Class")) {
+                    return parts[1].trim();
+                }
+            }
+            return null;
+        } catch (IOException e) {
+            return null;
+        }
+    }
+}