Limit which classes are retransformed (#118786)

During entitlements initialization the transformer is added to
instrumenation after some classes are already loaded. Currently we end
up force loading (though not initializing) all classes that want to
transform. This commit simplifies the retransform to only apply to
classes which we know are already loaded by the jdk, which
Instrumentation provides.

Author: rjernst

libs/entitlement/src/main/java/org/elasticsearch/entitlement/initialization/EntitlementInitialization.java

@@ -34,6 +34,7 @@
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardOpenOption;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashMap;
 import java.util.List;
@@ -72,17 +73,17 @@ public static void initialize(Instrumentation inst) throws Exception {
 
         Instrumenter instrumenter = INSTRUMENTER_FACTORY.newInstrumenter(EntitlementChecker.class, checkMethods);
         inst.addTransformer(new Transformer(instrumenter, classesToTransform), true);
-        // TODO: should we limit this array somehow?
-        var classesToRetransform = classesToTransform.stream().map(EntitlementInitialization::internalNameToClass).toArray(Class[]::new);
-        inst.retransformClasses(classesToRetransform);
+        inst.retransformClasses(findClassesToRetransform(inst.getAllLoadedClasses(), classesToTransform));
     }
 
-    private static Class<?> internalNameToClass(String internalName) {
-        try {
-            return Class.forName(internalName.replace('/', '.'), false, ClassLoader.getPlatformClassLoader());
-        } catch (ClassNotFoundException e) {
-            throw new RuntimeException(e);
+    private static Class<?>[] findClassesToRetransform(Class<?>[] loadedClasses, Set<String> classesToTransform) {
+        List<Class<?>> retransform = new ArrayList<>();
+        for (Class<?> loadedClass : loadedClasses) {
+            if (classesToTransform.contains(loadedClass.getName().replace(".", "/"))) {
+                retransform.add(loadedClass);
+            }
         }
+        return retransform.toArray(new Class<?>[0]);
     }
 
     private static PolicyManager createPolicyManager() throws IOException {