Feature/support auto generated timestamp in nested objects

.changes/next-release/feature-AmazonDynamoDBEnhancedClient-381e9b3.json

@@ -0,0 +1,6 @@
+{
+    "type": "feature",
+    "category": "Amazon DynamoDB Enhanced Client",
+    "contributor": "",
+    "description": "Added support for DynamoDbAutoGeneratedTimestampAttribute annotation in nested objects."
+}

services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/extensions/AutoGeneratedTimestampRecordExtension.java

@@ -20,8 +20,11 @@
 import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
+import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.function.Consumer;
+import java.util.stream.Collectors;
 import software.amazon.awssdk.annotations.NotThreadSafe;
 import software.amazon.awssdk.annotations.SdkPublicApi;
 import software.amazon.awssdk.annotations.ThreadSafe;
@@ -30,6 +33,7 @@
 import software.amazon.awssdk.enhanced.dynamodb.DynamoDbEnhancedClientExtension;
 import software.amazon.awssdk.enhanced.dynamodb.DynamoDbExtensionContext;
 import software.amazon.awssdk.enhanced.dynamodb.EnhancedType;
+import software.amazon.awssdk.enhanced.dynamodb.TableSchema;
 import software.amazon.awssdk.enhanced.dynamodb.mapper.StaticAttributeTag;
 import software.amazon.awssdk.enhanced.dynamodb.mapper.StaticTableMetadata;
 import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
@@ -126,28 +130,70 @@ public static AutoGeneratedTimestampRecordExtension create() {
      */
     @Override
     public WriteModification beforeWrite(DynamoDbExtensionContext.BeforeWrite context) {
+        Collection customMetadataObject = context.tableMetadata()
+                                                 .customMetadataObject(CUSTOM_METADATA_KEY, Collection.class).orElse(null);
 
-        Collection<String> customMetadataObject = context.tableMetadata()
-                                       .customMetadataObject(CUSTOM_METADATA_KEY, Collection.class).orElse(null);
+        Map<String, AttributeValue> itemToTransform = new HashMap<>(context.items());
+        if (customMetadataObject != null) {
+            customMetadataObject.forEach(
+                key -> insertTimestampInItemToTransform(itemToTransform, key.toString(),
+                                                        context.tableSchema().converterForAttribute(key)));
+        }
+        itemToTransform.forEach((key, value) -> {
+            if (value.hasM() && value.m() != null) {
+                Optional<? extends TableSchema<?>> nestedSchema = getNestedSchema(context.tableSchema(), key);
+                if (nestedSchema != null && nestedSchema.isPresent()) {
+                    itemToTransform.put(key, AttributeValue.builder().m(processNestedObject(value.m(), nestedSchema.get())).build());
+                }
+            }
+        });
 
-        if (customMetadataObject == null) {
+        if (itemToTransform.isEmpty()) {
             return WriteModification.builder().build();
         }
-        Map<String, AttributeValue> itemToTransform = new HashMap<>(context.items());
-        customMetadataObject.forEach(
-            key -> insertTimestampInItemToTransform(itemToTransform, key,
-                                                    context.tableSchema().converterForAttribute(key)));
         return WriteModification.builder()
                                 .transformedItem(Collections.unmodifiableMap(itemToTransform))
                                 .build();
     }
 
+    private Map<String, AttributeValue> processNestedObject(Map<String, AttributeValue> nestedMap, TableSchema<?> nestedSchema) {
+        Map<String, AttributeValue> updatedNestedMap = new HashMap<>(nestedMap);
+        Collection customMetadataObject = nestedSchema.tableMetadata()
+                                                      .customMetadataObject(CUSTOM_METADATA_KEY, Collection.class).orElse(null);
+        for (Map.Entry<String, AttributeValue> entry : nestedMap.entrySet()) {
+            String nestedKey = entry.getKey();
+            AttributeValue nestedValue = entry.getValue();
+
+            if (nestedValue.hasM()) {
+                updatedNestedMap.put(nestedKey,
+                                     AttributeValue.builder().m(processNestedObject(nestedValue.m(), nestedSchema)).build());
+            } else if (nestedValue.hasL()) {
+                List<AttributeValue> updatedList = nestedValue.l().stream()
+                                                              .map(listItem -> listItem.hasM() ?
+                                                                               AttributeValue.builder().m(processNestedObject(listItem.m(), nestedSchema)).build() : listItem)
+                                                              .collect(Collectors.toList());
+                updatedNestedMap.put(nestedKey, AttributeValue.builder().l(updatedList).build());
+            } else {
+                AttributeConverter<?> converter = nestedSchema.converterForAttribute(nestedKey);
+                if (converter != null && customMetadataObject != null && customMetadataObject.contains(nestedKey)) {
+                    insertTimestampInItemToTransform(updatedNestedMap, nestedKey, converter);
+                }
+            }
+        }
+        return updatedNestedMap;
+    }
+
+
     private void insertTimestampInItemToTransform(Map<String, AttributeValue> itemToTransform,
                                                   String key,
                                                   AttributeConverter converter) {
         itemToTransform.put(key, converter.transformFrom(clock.instant()));
     }
 
+    private Optional<? extends TableSchema<?>> getNestedSchema(TableSchema<?> parentSchema, String attributeName) {
+        return parentSchema.converterForAttribute(attributeName).type().tableSchema();
+    }
+
     /**
      *  Builder for a {@link AutoGeneratedTimestampRecordExtension}
      */