turns out proxy delegate access is not needed

Author: SylvainJuge

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

@@ -17,7 +17,6 @@
 import io.opentelemetry.context.Scope;
 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;
@@ -62,20 +61,13 @@ public static class HandlerMappingAdvice {
     public static void afterRefresh(
         @Advice.Argument(0) ApplicationContext springCtx,
         @Advice.FieldValue("handlerMappings") List<HandlerMapping> handlerMappings) {
-      if (springCtx.containsBean("otelAutoDispatcherFilter")) {
-        Object bean = springCtx.getBean("otelAutoDispatcherFilter");
-        try {
-          // the bean is a proxy of OpenTelemetryHandlerMappingFilter, so we need to access the
-          // proxied object, trying to use reflection to invoke methods triggers stack overflows
-          Field delegate = bean.getClass().getField("delegate");
-          Object delegateObject = delegate.get(bean);
-          OpenTelemetryHandlerMappingFilter mappingFilter =
-              (OpenTelemetryHandlerMappingFilter) delegateObject;
-          mappingFilter.setHandlerMappings(handlerMappings);
-        } catch (IllegalAccessException | NoSuchFieldException e) {
-          throw new IllegalStateException(e);
-        }
+
+      if (handlerMappings == null || !springCtx.containsBean("otelAutoDispatcherFilter")) {
+        return;
       }
+      OpenTelemetryHandlerMappingFilter filter =
+          springCtx.getBean("otelAutoDispatcherFilter", 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

@@ -17,7 +17,6 @@
 import io.opentelemetry.context.Scope;
 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;
@@ -63,21 +62,15 @@ public static void afterRefresh(
         @Advice.Argument(0) ApplicationContext springCtx,
         @Advice.FieldValue("handlerMappings") List<HandlerMapping> handlerMappings) {
 
-      if (springCtx.containsBean("otelAutoDispatcherFilter")) {
-        Object bean = springCtx.getBean("otelAutoDispatcherFilter");
-        try {
-          // the bean is a proxy of OpenTelemetryHandlerMappingFilter, so we need to access the
-          // proxied object, trying to use reflection to invoke methods triggers stack overflows
-          Field delegate = bean.getClass().getField("delegate");
-          Object delegateObject = delegate.get(bean);
-          OpenTelemetryHandlerMappingFilter mappingFilter =
-              (OpenTelemetryHandlerMappingFilter) delegateObject;
-          mappingFilter.setHandlerMappings(handlerMappings);
-        } catch (IllegalAccessException | NoSuchFieldException e) {
-          throw new IllegalStateException(e);
-        }
+      if (handlerMappings == null || !springCtx.containsBean("otelAutoDispatcherFilter")) {
+        return;
       }
+
+      OpenTelemetryHandlerMappingFilter filter = springCtx.getBean("otelAutoDispatcherFilter",
+          OpenTelemetryHandlerMappingFilter.class);
+      filter.setHandlerMappings(handlerMappings);
     }
+
   }
 
   @SuppressWarnings("unused")

javaagent-tooling/src/main/java/io/opentelemetry/javaagent/tooling/instrumentation/indy/IndyProxyFactory.java

@@ -93,8 +93,7 @@ public DynamicType.Unloaded<?> generateProxy(
             .implement(classToProxy.getInterfaces())
             .name(proxyClassName)
             .annotateType(classToProxy.getDeclaredAnnotations())
-            // field must be public to enable resolving the proxy target using introspection
-            .defineField(DELEGATE_FIELD_NAME, Object.class, Modifier.PUBLIC | Modifier.FINAL);
+            .defineField(DELEGATE_FIELD_NAME, Object.class, Modifier.PRIVATE | Modifier.FINAL);
 
     for (MethodDescription.InDefinedShape method : classToProxy.getDeclaredMethods()) {
       if (method.isPublic()) {