Resolve the issue of failing to retrieve attachments in dubbo 2.7.6 and 2.7.7

instrumentation/apache-dubbo-2.7/library-autoconfigure/src/main/java/io/opentelemetry/instrumentation/apachedubbo/v2_7/DubboHeadersGetter.java

@@ -6,14 +6,31 @@
 package io.opentelemetry.instrumentation.apachedubbo.v2_7;
 
 import io.opentelemetry.context.propagation.TextMapGetter;
+import java.lang.reflect.Method;
+import java.util.Map;
+import java.util.Set;
+import org.apache.dubbo.rpc.RpcInvocation;
 
 enum DubboHeadersGetter implements TextMapGetter<DubboRequest> {
   INSTANCE;
 
   @Override
-  @SuppressWarnings("deprecation") // deprecation for dubbo 3.2.15
+  @SuppressWarnings("unchecked") // unchecked for 2.7.6, 2.7.7
   public Iterable<String> keys(DubboRequest request) {
-    return request.invocation().getAttachments().keySet();
+    RpcInvocation invocation = request.invocation();
+    Map<String, String> attachments = invocation.getAttachments();
+    Set<String> keys = invocation.getAttachments().keySet();
+    // In 2.7.6, 2.7.7, the StringToObjectMap implementation does not correctly retrieve the keySet.
+    if (keys.size() == 0 && "ObjectToStringMap".equals(attachments.getClass().getSimpleName())) {
+      Method getObjectAttachmentsMethod = null;
+      try {
+        getObjectAttachmentsMethod = invocation.getClass().getMethod("getObjectAttachments");
+        return ((Map<String, Object>) getObjectAttachmentsMethod.invoke(invocation)).keySet();
+      } catch (Exception e) {
+        // ignore
+      }
+    }
+    return keys;
   }
 
   @Override