refactor(rmi): convert Helper.narrow() to MethodHandle with caching

Convert Method.invoke() to MethodHandle.invoke() for IDL Helper narrow()
calls in PortableRemoteObjectImpl with ClassValue-based caching.

Changes:
- Added HELPER_NARROW_CACHE using ClassValue<MethodHandle>, mapping from
  helper class to its "narrow" method
- Updated narrowIDL() to use cached MethodHandle instead of Method.invoke()
- Simplified exception handling with consistent pattern
- Updated MultiAddressUrlTest to remove InvocationTargetException from expected causal chains, as MethodHandle.invoke() does not add this wrapper layer (unlike the old Method.invoke() approach)
- Fixed exception handling in StubWriteReplaceMethodHolder to properly unwrap PrivilegedActionException
- Lines added: 29, lines removed: 13

Performance: ClassValue provides thread-safe per-class caching without locks

Co-authored-by: Joe Chacko <chackoj@uk.ibm.com>
Co-authored-by-AI: IBM Bob 1.0.4

Author: ngmr

yoko-rmi-impl/src/main/java/org/apache/yoko/rmi/impl/PortableRemoteObjectImpl.java

@@ -34,6 +34,8 @@
 import javax.rmi.CORBA.Stub;
 import javax.rmi.CORBA.Tie;
 import javax.rmi.CORBA.Util;
+import java.lang.invoke.MethodHandle;
+import java.lang.invoke.MethodHandles;
 import java.lang.reflect.Constructor;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
@@ -66,13 +68,26 @@ enum StubWriteReplaceMethodHolder {
         static {
             try {
                 STUB_WRITE_REPLACE_METHOD = doPrivileged(getDeclaredMethod(RMIStub.class, "writeReplace"));
-            } catch (PrivilegedActionException ex) {
-                //noinspection Convert2MethodRef
-                throw wrapped(LOGGER, ex, "cannot initialize: \n" + ex.getMessage(), e -> new Error(e));
+            } catch (PrivilegedActionException pae) {
+                Throwable t = pae.getCause();
+                throw wrapped(LOGGER, t, "cannot initialize: \n" + t.getMessage(), e -> new Error(t));
             }
         }
     }
 
+
+    private static final ClassValue<MethodHandle> HELPER_NARROW_CACHE = new ClassValue<MethodHandle>() {
+        @Override
+        protected MethodHandle computeValue(Class<?> helperClass) {
+            try {
+                final Method helperNarrow = doPrivileged(getMethod(helperClass, "narrow", org.omg.CORBA.Object.class));
+                return MethodHandles.lookup().unreflect(helperNarrow);
+            } catch (Exception e) {
+                throw as(ClassCastException::new, e, helperClass.getName());
+            }
+        }
+    };
+
     public void connect(Remote target, Remote source) throws RemoteException {
         source = toStub(source);
 
@@ -126,15 +141,16 @@ private Object narrowRMI(ObjectImpl narrowFrom, Class<?> narrowTo) {
 
     private Object narrowIDL(ObjectImpl narrowFrom, Class<?> narrowTo) {
         LOGGER.fine(() -> String.format("IDL narrowing %s => %s", narrowFrom.getClass().getName(), narrowTo.getName()));
-        final ClassLoader idlClassLoader = doPrivileged(getClassLoader(narrowTo));
-        final String helperClassName = narrowTo.getName() + "Helper";
-
         try {
+            final ClassLoader idlClassLoader = doPrivileged(getClassLoader(narrowTo));
+            final String helperClassName = narrowTo.getName() + "Helper";
             final Class<?> helperClass = Util.loadClass(helperClassName, null, idlClassLoader);
-            final Method helperNarrow = doPrivileged(getMethod(helperClass, "narrow", org.omg.CORBA.Object.class));
-            return helperNarrow.invoke(null, narrowFrom);
-        } catch (Exception e) {
-            throw as(ClassCastException::new, e, narrowTo.getName());
+            MethodHandle narrowHandle = HELPER_NARROW_CACHE.get(helperClass);
+            return narrowHandle.invoke(narrowFrom);
+        } catch (Error e) {
+            throw e;
+        } catch (Throwable t) {
+            throw as(ClassCastException::new, t, narrowTo.getName());
         }
     }
 
@@ -239,7 +255,7 @@ static Constructor<? extends Stub> getRMIStubClassConstructor(RMIState state, Cl
             return cachedCons;
         }
 
-        
+
         final ClassLoader loader = doPrivileged(getClassLoader(type));
         final ClassLoader contextLoader = doPrivileged(GET_CONTEXT_CLASS_LOADER);
 

yoko-verify/src/test/java-testify/org/apache/yoko/MultiAddressUrlTest.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2025 IBM Corporation and others.
+ * Copyright 2026 IBM Corporation and others.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -65,14 +65,14 @@ public void testServerStopped(ORB orb) {
         narrow(orb.string_to_object(nsUrl), NamingContext.class);
         // stop the server
         control.stop();
-        assertThrowsExactly(ClassCastException.class, () -> narrow(orb.string_to_object(nsUrl), NamingContext.class), InvocationTargetException.class, TRANSIENT.class, ConnectException.class);
+        assertThrowsExactly(ClassCastException.class, () -> narrow(orb.string_to_object(nsUrl), NamingContext.class), TRANSIENT.class, ConnectException.class);
         control.start();
     }
 
     @Test
     public void testConnectionRefused(ORB orb) throws Exception {
         // first show that port 47 is not listening
-        assertThrowsExactly(ClassCastException.class, () -> narrow(orb.string_to_object(NO_LISTENER_NS_URL), NamingContext.class), InvocationTargetException.class, TRANSIENT.class, ConnectException.class);
+        assertThrowsExactly(ClassCastException.class, () -> narrow(orb.string_to_object(NO_LISTENER_NS_URL), NamingContext.class), TRANSIENT.class, ConnectException.class);
         // check our nsURL starts with corbaname:
         assertThat(nsUrl, startsWith("corbaname:"));
         // construct a URL where the first server is stopped (connection refused)
@@ -84,7 +84,7 @@ public void testConnectionRefused(ORB orb) throws Exception {
     @Test
     public void testHostUnreachable(ORB orb) throws Exception {
         // first show that port 47 is not listening
-        assertThrowsExactly(ClassCastException.class, () -> narrow(orb.string_to_object(UNREACHABLE_NS_URL), NamingContext.class), InvocationTargetException.class, NO_RESPONSE.class);
+        assertThrowsExactly(ClassCastException.class, () -> narrow(orb.string_to_object(UNREACHABLE_NS_URL), NamingContext.class), NO_RESPONSE.class);
         // check our nsURL starts with corbaname:
         assertThat(nsUrl, startsWith("corbaname:"));
         // construct a URL where the first server is stopped (connection refused)