Add feature flag

Author: hyerans

core/src/main/java/org/mule/runtime/core/internal/context/DefaultMuleContext.java

@@ -39,6 +39,7 @@
 import static org.mule.runtime.api.config.MuleRuntimeFeature.PARALLEL_FOREACH_FLATTEN_MESSAGE;
 import static org.mule.runtime.api.config.MuleRuntimeFeature.PUT_TRACE_ID_AND_SPAN_ID_IN_MDC;
 import static org.mule.runtime.api.config.MuleRuntimeFeature.RETHROW_EXCEPTIONS_IN_IDEMPOTENT_MESSAGE_VALIDATOR;
+import static org.mule.runtime.api.config.MuleRuntimeFeature.SEPARATE_CLASSLOADER_FOR_POLICY_ISOLATION;
 import static org.mule.runtime.api.config.MuleRuntimeFeature.SET_VARIABLE_WITH_NULL_VALUE;
 import static org.mule.runtime.api.config.MuleRuntimeFeature.START_EXTENSION_COMPONENTS_WITH_ARTIFACT_CLASSLOADER;
 import static org.mule.runtime.api.config.MuleRuntimeFeature.SUPPRESS_ERRORS;
@@ -343,6 +344,7 @@ public class DefaultMuleContext implements MuleContextWithRegistry, PrivilegedMu
       configureComputeConnectionErrorsInStats();
       configureToStringTransformerTransformIteratorElements();
       configureEnablePolicyIsolation();
+      configureSeparateClassLoaderForPolicyIsolation();
       configureEntityResolverFailOnFirstErrorFeature();
       configureEnableProfilingService();
       configureSetVariableWithNullVale();
@@ -1305,6 +1307,17 @@ private static void configureEnablePolicyIsolation() {
                                                 minMuleVersion(v4_4_0));
   }
 
+  /**
+   * Configures the {@link MuleRuntimeFeature#SEPARATE_CLASSLOADER_FOR_POLICY_ISOLATION} feature flag.
+   *
+   * @since 4.6.0
+   */
+  private static void configureSeparateClassLoaderForPolicyIsolation() {
+    FeatureFlaggingRegistry featureFlaggingRegistry = FeatureFlaggingRegistry.getInstance();
+    featureFlaggingRegistry.registerFeatureFlag(SEPARATE_CLASSLOADER_FOR_POLICY_ISOLATION,
+                                                minMuleVersion(v4_6_0));
+  }
+
   /**
    * Configures the {@link MuleRuntimeFeature#ENTITY_RESOLVER_FAIL_ON_FIRST_ERROR} feature flag.
    *

modules/deployment-model-impl/src/main/java/org/mule/runtime/module/deployment/impl/internal/policy/DefaultPolicyTemplateFactory.java

@@ -7,6 +7,7 @@
 package org.mule.runtime.module.deployment.impl.internal.policy;
 
 import static org.mule.runtime.api.config.MuleRuntimeFeature.ENABLE_POLICY_ISOLATION;
+import static org.mule.runtime.api.config.MuleRuntimeFeature.SEPARATE_CLASSLOADER_FOR_POLICY_ISOLATION;
 import static org.mule.runtime.api.util.Preconditions.checkArgument;
 import static org.mule.runtime.deployment.model.internal.DefaultRegionPluginClassLoadersFactory.getArtifactPluginId;
 import static org.mule.runtime.module.artifact.api.classloader.DefaultArtifactClassLoaderFilter.NULL_CLASSLOADER_FILTER;
@@ -123,11 +124,13 @@ public PolicyTemplate createArtifact(Application application, PolicyTemplateDesc
                                                                ownPolicyClassLoader));
   }
 
+  // Use additional feature flag SEPARATE_CLASSLOADER_FOR_POLICY_ISOLATION,
+  // so that we can use isolated classloader as parent classloader, only when this feature is enabled.
   private boolean isPolicyIsolationEnabled(PolicyTemplateDescriptor descriptor) {
-    return isFeatureEnabled(ENABLE_POLICY_ISOLATION, descriptor);
+    return isFeatureEnabled(ENABLE_POLICY_ISOLATION, descriptor) &&
+        isFeatureEnabled(SEPARATE_CLASSLOADER_FOR_POLICY_ISOLATION, descriptor);
   }
 
-  //
   private boolean hasRequiredPlugin(PolicyTemplateDescriptor descriptor) {
     if (descriptor == null || descriptor.getPlugins() == null) {
       return false;