Replace ScriptRuntime#main(String scriptClassName, String[] args) by ScriptRuntime#main(Class scriptClass, String[] args) and to optimizer.Codegen#generateMain code to generate call to Class.forName before calling ScriptRuntime#main. In this way script byte code can access Class object if generated script is loaded via different class loader then Rhino classes.

js/rhino/src/org/mozilla/javascript/ScriptRuntime.java

@@ -1818,34 +1818,31 @@ public class ScriptRuntime {
         return new ImporterTopLevel(cx);
     }
 
-    public static void main(String scriptClassName, String[] args)
+    public static void main(Class scriptClass, String[] args)
         throws JavaScriptException
     {
         Context cx = Context.enter();
-        ScriptableObject global = getGlobal(cx);
-
-        // get the command line arguments and define "arguments"
-        // array in the top-level object
-        Scriptable argsObj = cx.newArray(global, args);
-        global.defineProperty("arguments", argsObj,
-                              ScriptableObject.DONTENUM);
-
         try {
-            Class cl = loadClassName(scriptClassName);
-            Script script = (Script) cl.newInstance();
+            Script script = null;
+            try {
+                script = (Script)scriptClass.newInstance();
+            } catch (InstantiationException e) {
+            } catch (IllegalAccessException e) {
+            }
+            if (script == null) {
+                throw new RuntimeException("Error creating script object");
+            }
+            ScriptableObject global = getGlobal(cx);
+
+            // get the command line arguments and define "arguments"
+            // array in the top-level object
+            Scriptable argsObj = cx.newArray(global, args);
+            global.defineProperty("arguments", argsObj,
+                                  ScriptableObject.DONTENUM);
             script.exec(cx, global);
-            return;
-        }
-        catch (ClassNotFoundException e) {
-        }
-        catch (InstantiationException e) {
-        }
-        catch (IllegalAccessException e) {
-        }
-        finally {
+        } finally {
             Context.exit();
         }
-        throw new RuntimeException("Error creating script object");
     }
 
     public static Scriptable initScript(Context cx, Scriptable scope,

js/rhino/src/org/mozilla/javascript/optimizer/Codegen.java

@@ -1018,15 +1018,19 @@ public class Codegen extends Interpreter {
         startNewMethod("main", "([Ljava/lang/String;)V", 1, true, true);
 
         push(this.name);        // load the name of this class
+        classFile.add(ByteCode.INVOKESTATIC,
+                      "java/lang/Class",
+                      "forName",
+                      "(Ljava/lang/String;)",
+                      "Ljava/lang/Class;");
         addByteCode(ByteCode.ALOAD_0); // load 'args'
         addScriptRuntimeInvoke("main",
-                              "(Ljava/lang/String;[Ljava/lang/String;)",
+                              "(Ljava/lang/Class;[Ljava/lang/String;)",
                               "V");
         addByteCode(ByteCode.RETURN);
         finishMethod(cx, null);
     }
 
-
     private void generateExecute(Context cx) {
         String signature = "(Lorg/mozilla/javascript/Context;" +
                             "Lorg/mozilla/javascript/Scriptable;)" +