another attempt with helper class

Author: SylvainJuge

instrumentation/spring/spring-webmvc/spring-webmvc-3.1/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/spring/webmvc/v3_1/DispatcherServletInstrumentation.java

@@ -15,9 +15,9 @@
 
 import io.opentelemetry.context.Context;
 import io.opentelemetry.context.Scope;
+import io.opentelemetry.javaagent.bootstrap.IndyProxyHelper;
 import io.opentelemetry.javaagent.extension.instrumentation.TypeInstrumentation;
 import io.opentelemetry.javaagent.extension.instrumentation.TypeTransformer;
-import java.lang.reflect.Field;
 import java.util.List;
 import net.bytebuddy.asm.Advice;
 import net.bytebuddy.description.type.TypeDescription;
@@ -73,13 +73,7 @@ public static void afterRefresh(
         // inline advice: no proxy class is used
         filter = (OpenTelemetryHandlerMappingFilter) bean;
       } else {
-        // non-inlined advice: proxy class is used
-        try {
-          Field delegate = bean.getClass().getField("delegate");
-          filter = (OpenTelemetryHandlerMappingFilter) delegate.get(bean);
-        } catch (NoSuchFieldException | IllegalAccessException e) {
-          throw new IllegalStateException(e);
-        }
+        filter = IndyProxyHelper.unwrapIfNeeded(bean, OpenTelemetryHandlerMappingFilter.class);
       }
       filter.setHandlerMappings(handlerMappings);
     }

instrumentation/spring/spring-webmvc/spring-webmvc-6.0/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/spring/webmvc/v6_0/DispatcherServletInstrumentation.java

@@ -15,9 +15,9 @@
 
 import io.opentelemetry.context.Context;
 import io.opentelemetry.context.Scope;
+import io.opentelemetry.javaagent.bootstrap.IndyProxyHelper;
 import io.opentelemetry.javaagent.extension.instrumentation.TypeInstrumentation;
 import io.opentelemetry.javaagent.extension.instrumentation.TypeTransformer;
-import java.lang.reflect.Field;
 import java.util.List;
 import net.bytebuddy.asm.Advice;
 import net.bytebuddy.description.type.TypeDescription;
@@ -74,13 +74,7 @@ public static void afterRefresh(
         // inline advice: no proxy class is used
         filter = (OpenTelemetryHandlerMappingFilter) bean;
       } else {
-        // non-inlined advice: proxy class is used
-        try {
-          Field delegate = bean.getClass().getField("delegate");
-          filter = (OpenTelemetryHandlerMappingFilter) delegate.get(bean);
-        } catch (NoSuchFieldException | IllegalAccessException e) {
-          throw new IllegalStateException(e);
-        }
+        filter = IndyProxyHelper.unwrapIfNeeded(bean, OpenTelemetryHandlerMappingFilter.class);
       }
       filter.setHandlerMappings(handlerMappings);
     }

javaagent-bootstrap/src/main/java/io/opentelemetry/javaagent/bootstrap/IndyProxyHelper.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.javaagent.bootstrap;
+
+import java.lang.reflect.Field;
+
+public class IndyProxyHelper {
+
+  private IndyProxyHelper() {
+  }
+
+  public static <T> T unwrapIfNeeded(Object o, Class<T> type) {
+    if (type.isAssignableFrom(o.getClass())) {
+      return type.cast(o);
+    }
+    // public delegate field on indy proxy
+    try {
+      Field delegateField = o.getClass().getField("delegate");
+      Object delegate = delegateField.get(o);
+      if (type.isAssignableFrom(delegate.getClass())) {
+        return type.cast(delegate);
+      }
+    } catch (NoSuchFieldException | IllegalAccessException e) {
+      throw new IllegalStateException(e);
+    }
+
+    return null;
+  }
+}