Remove reflection from ensureClassInitialized, fix <clinit> ordering

Replace the reflective initialize() fallback in ensureClassInitialized()
with a pure Class.forName() approach. The recursive <clinit> issue in
CosmosItemSerializer is fixed by moving 'static { initialize(); }' before
the DEFAULT_SERIALIZER field, so the accessor is registered before
DefaultCosmosItemSerializer's <clinit> needs it.

ensureClassInitialized() is now a clean 3-line method with no reflection.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: jeet1995

sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/CosmosItemSerializer.java

@@ -30,6 +30,9 @@
  */
 public abstract class CosmosItemSerializer {
 
+    // Register the accessor before any static fields that may trigger other classes'
+    // <clinit> which need this accessor (e.g., DefaultCosmosItemSerializer).
+    static { initialize(); }
 
     /**
      * Gets the default Cosmos item serializer. This serializer is used by default when no custom serializer is
@@ -163,6 +166,4 @@ public ObjectMapper getItemObjectMapper(CosmosItemSerializer serializer) {
                 }
             });
     }
-
-    static { initialize(); }
 }

sdk/cosmos/azure-cosmos/src/main/java/com/azure/cosmos/implementation/ImplementationBridgeHelpers.java

@@ -123,24 +123,11 @@ public static void initializeAllAccessors() {
      */
     private static void ensureClassInitialized(String className) {
         try {
-            Class<?> cls = Class.forName(className, true, ImplementationBridgeHelpers.class.getClassLoader());
-            // Class.forName triggers <clinit> for first-time loading. However, during recursive
-            // <clinit> from the same thread (e.g., CosmosItemSerializer.<clinit> → DefaultCosmosItemSerializer
-            // → getCosmosItemSerializerAccessor() → ensureClassInitialized("CosmosItemSerializer")),
-            // Class.forName is a no-op per JLS §12.4.2. In that case the accessor hasn't been registered
-            // yet. Calling initialize() as a regular static method IS allowed during recursive <clinit>
-            // from the same thread and will explicitly register the accessor.
-            java.lang.reflect.Method initMethod = cls.getDeclaredMethod("initialize");
-            initMethod.setAccessible(true);
-            initMethod.invoke(null);
+            Class.forName(className, true, ImplementationBridgeHelpers.class.getClassLoader());
         } catch (ClassNotFoundException e) {
             logger.error("Failed to load class for accessor initialization: {}", className, e);
             throw new IllegalStateException(
                 "Unable to load class for accessor initialization: " + className, e);
-        } catch (NoSuchMethodException e) {
-            // Not all classes have an initialize() method — Class.forName alone suffices for those
-        } catch (java.lang.reflect.InvocationTargetException | IllegalAccessException e) {
-            logger.debug("Could not invoke initialize() on {}: {}", className, e.getMessage());
         }
     }