Updated after handling Matt's comments

Author: joviegas

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

@@ -86,14 +86,13 @@ static <T> BeanTableSchema<T> fromBean(Class<T> beanClass) {
         return BeanTableSchema.create(beanClass);
     }
 
-
     /**
-     * Provides interfaces to interact with DynamoDB tables as {@link EnhancedDocument} where the complete Schema of the table
-     * is not required.
-     * @return A {@link DocumentTableSchema.Builder} for instantiating DocumentTableSchema.
+     * Provides interfaces to interact with DynamoDB tables as {@link EnhancedDocument} where the complete Schema of the table is
+     * not required.
      *
+     * @return A {@link DocumentTableSchema.Builder} for instantiating DocumentTableSchema.
      */
-    static DocumentTableSchema.Builder documentSchemaBuilder(){
+    static DocumentTableSchema.Builder documentSchemaBuilder() {
         return DocumentTableSchema.builder();
     }
 

services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/document/EnhancedDocument.java

@@ -73,6 +73,9 @@ public AttributeValue transformFrom(JsonNode input) {
 
     @Override
     public JsonNode transformTo(AttributeValue input) {
+        if (AttributeValue.fromNul(true).equals(input)) {
+            return NullJsonNode.instance();
+        }
         return EnhancedAttributeValue.fromAttributeValue(input).convert(VISITOR);
     }
 

services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/internal/converter/attribute/JsonItemAttributeConverter.java

@@ -38,7 +38,7 @@ public static JsonNodeToAttributeValueMapConverter instance() {
 
     @Override
     public AttributeValue visitNull() {
-        return AttributeValue.builder().build();
+        return AttributeValue.fromNul(true);
     }
 
     @Override
@@ -70,7 +70,8 @@ public AttributeValue visitObject(Map<String, JsonNode> object) {
                                                 .collect(Collectors.toMap(
                                                     entry -> entry.getKey(),
                                                     entry -> entry.getValue().visit(this),
-                                                    (left, right) -> left, LinkedHashMap::new))).build();
+                                                    (left, right) -> left, LinkedHashMap::new)))
+                             .build();
     }
 
     @Override

services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/internal/converter/attribute/JsonNodeToAttributeValueMapConverter.java

@@ -15,7 +15,6 @@
 
 package software.amazon.awssdk.enhanced.dynamodb.internal.converter.attribute;
 
-import java.math.BigInteger;
 import software.amazon.awssdk.annotations.Immutable;
 import software.amazon.awssdk.annotations.SdkInternalApi;
 import software.amazon.awssdk.annotations.ThreadSafe;

services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/internal/converter/attribute/SdkNumberAttributeConverter.java

@@ -15,7 +15,6 @@
 
 package software.amazon.awssdk.enhanced.dynamodb.internal.converter.string;
 
-import java.math.BigInteger;
 import software.amazon.awssdk.annotations.Immutable;
 import software.amazon.awssdk.annotations.SdkInternalApi;
 import software.amazon.awssdk.annotations.ThreadSafe;

services-custom/dynamodb-enhanced/src/main/java/software/amazon/awssdk/enhanced/dynamodb/internal/converter/string/SdkNumberStringConverter.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+package software.amazon.awssdk.enhanced.dynamodb.internal.document;
+
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+import software.amazon.awssdk.annotations.SdkInternalApi;
+import software.amazon.awssdk.protocols.jsoncore.JsonNode;
+import software.amazon.awssdk.protocols.jsoncore.JsonNodeVisitor;
+
+@SdkInternalApi
+public class IdentityJsonNodeVisitor implements JsonNodeVisitor<Object> {
+    @Override
+    public Object visitNull() {
+        return null;
+    }
+
+    @Override
+    public Object visitBoolean(boolean bool) {
+        return bool;
+    }
+
+    @Override
+    public Object visitNumber(String number) {
+        return number;
+    }
+
+    @Override
+    public Object visitString(String string) {
+        return string;
+    }
+
+    @Override
+    public Object visitArray(List<JsonNode> array) {
+        return array.stream()
+                    .map(n -> n.visit(this))
+                    .collect(Collectors.toList());
+    }
+
+    @Override
+    public Object visitObject(Map<String, JsonNode> object) {
+        Map<String, Object> result = new LinkedHashMap<>(object.size());
+        object.forEach((k, v) -> {
+            result.put(k, v.visit(this));
+        });
+        return result;
+    }
+
+    @Override
+    public Object visitEmbeddedObject(Object embeddedObject) {
+        return embeddedObject;
+    }
+}