Convert null string to null attribute value

Author: zoewangg

.changes/next-release/bugfix-DynamoDBEnhancedClient-efd901b.json

@@ -0,0 +1,6 @@
+{
+    "category": "DynamoDB Enhanced Client", 
+    "contributor": "", 
+    "type": "bugfix", 
+    "description": "Converts string to NULL attribute if it's null. See [#2243](https://github.com/aws/aws-sdk-java-v2/issues/2243)"
+}

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

@@ -29,6 +29,7 @@
 import software.amazon.awssdk.enhanced.dynamodb.AttributeConverter;
 import software.amazon.awssdk.enhanced.dynamodb.AttributeValueType;
 import software.amazon.awssdk.enhanced.dynamodb.EnhancedType;
+import software.amazon.awssdk.enhanced.dynamodb.internal.AttributeValues;
 import software.amazon.awssdk.enhanced.dynamodb.internal.converter.TypeConvertingVisitor;
 import software.amazon.awssdk.enhanced.dynamodb.internal.converter.string.BooleanStringConverter;
 import software.amazon.awssdk.enhanced.dynamodb.internal.converter.string.ByteArrayStringConverter;
@@ -64,7 +65,7 @@ public AttributeValueType attributeValueType() {
 
     @Override
     public AttributeValue transformFrom(String input) {
-        return AttributeValue.builder().s(input).build();
+        return input == null ? AttributeValues.nullAttributeValue() : AttributeValue.builder().s(input).build();
     }
 
     @Override

services-custom/dynamodb-enhanced/src/test/java/software/amazon/awssdk/enhanced/dynamodb/converters/attribute/StringAttributeConvertersTest.java

@@ -40,6 +40,7 @@
 import org.junit.Test;
 import software.amazon.awssdk.core.SdkBytes;
 import software.amazon.awssdk.enhanced.dynamodb.AttributeValueType;
+import software.amazon.awssdk.enhanced.dynamodb.internal.AttributeValues;
 import software.amazon.awssdk.enhanced.dynamodb.internal.converter.attribute.CharSequenceAttributeConverter;
 import software.amazon.awssdk.enhanced.dynamodb.internal.converter.attribute.CharacterArrayAttributeConverter;
 import software.amazon.awssdk.enhanced.dynamodb.internal.converter.attribute.CharacterAttributeConverter;
@@ -128,6 +129,7 @@ public void stringAttributeConverterBehaves() {
         String chars = "foo";
         String numChars = "42";
 
+        assertThat(transformFrom(converter, null)).isSameAs(AttributeValues.nullAttributeValue());
         assertThat(transformFrom(converter, chars).s()).isSameAs(chars);
         assertThat(transformFrom(converter, emptyChars).s()).isSameAs(emptyChars);
 

services-custom/dynamodb-enhanced/src/test/java/software/amazon/awssdk/enhanced/dynamodb/mapper/BeanTableSchemaTest.java

@@ -845,6 +845,35 @@ public void mapBean_stringStringMap() {
         assertThat(reverse, is(equalTo(mapBean)));
     }
 
+    @Test
+    public void mapBean_mapWithNullValue() {
+        BeanTableSchema<MapBean> beanTableSchema = BeanTableSchema.create(MapBean.class);
+        MapBean mapBean = new MapBean();
+        mapBean.setId("id-value");
+
+        Map<String, String> testMap = new HashMap<>();
+        testMap.put("one", null);
+        testMap.put("three", "four");
+
+        mapBean.setStringMap(testMap);
+
+        Map<String, AttributeValue> itemMap = beanTableSchema.itemToMap(mapBean, true);
+
+        Map<String, AttributeValue> expectedMap = new HashMap<>();
+        expectedMap.put("one", AttributeValues.nullAttributeValue());
+        expectedMap.put("three", stringValue("four"));
+        AttributeValue expectedMapValue = AttributeValue.builder()
+                                                        .m(expectedMap)
+                                                        .build();
+
+        assertThat(itemMap.size(), is(2));
+        assertThat(itemMap, hasEntry("id", stringValue("id-value")));
+        assertThat(itemMap, hasEntry("stringMap", expectedMapValue));
+
+        MapBean reverse = beanTableSchema.mapToItem(itemMap);
+        assertThat(reverse, is(equalTo(mapBean)));
+    }
+
     @Test
     public void mapBean_nestedStringMap() {
         BeanTableSchema<MapBean> beanTableSchema = BeanTableSchema.create(MapBean.class);

services-custom/dynamodb-enhanced/src/test/java/software/amazon/awssdk/enhanced/dynamodb/mapper/StaticTableSchemaTest.java

@@ -1216,6 +1216,24 @@ public void mapperCanHandleGenericMap() {
                                 AttributeValue.builder().m(attributeValueMap).build());
     }
 
+    @Test
+    public void mapperCanHandleMapWithNullValue() {
+        Map<String, String> stringMap = new HashMap<>();
+        stringMap.put("one", null);
+        stringMap.put("two", "three");
+
+        Map<String, AttributeValue> attributeValueMap = new HashMap<>();
+        attributeValueMap.put("one", AttributeValue.builder().nul(true).build());
+        attributeValueMap.put("two", AttributeValue.builder().s("three").build());
+
+        verifyNullableAttribute(EnhancedType.mapOf(String.class, String.class),
+                                a -> a.name("value")
+                                      .getter(FakeMappedItem::getAStringMap)
+                                      .setter(FakeMappedItem::setAStringMap),
+                                FakeMappedItem.builder().aStringMap(stringMap).build(),
+                                AttributeValue.builder().m(attributeValueMap).build());
+    }
+
     @Test
     public void mapperCanHandleIntDoubleMap() {
         Map<Integer, Double> intDoubleMap = new ConcurrentHashMap<>();