EnumAttributeConverter: enums can be identified by toString() or name(). toString() is the default for backward compatibility

Author: martinKindall

.changes/next-release/bugfix-AmazonDynamoDB-2bb1833.json

@@ -0,0 +1,6 @@
+{
+    "category": "Amazon DynamoDB", 
+    "contributor": "martinKindall",
+    "type": "bugfix", 
+    "description": "Created static method EnumAttributeConverter::createWithNameAsKeys which creates a converter based on the Enum::name method to identify enums, rather than Enum::toString. This is preferable because Enum::name is final and cannot be overwritten, as opposed to Enum::toString. EnumAttributeConverter::create is kept as it is, for backward compatibility."
+}

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

@@ -19,6 +19,7 @@
 import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.Map;
+import java.util.function.Function;
 import software.amazon.awssdk.annotations.SdkInternalApi;
 import software.amazon.awssdk.enhanced.dynamodb.AttributeConverter;
 import software.amazon.awssdk.enhanced.dynamodb.AttributeValueType;
@@ -33,6 +34,12 @@
  * This stores values in DynamoDB as a string.
  *
  * <p>
+ * Use EnumAttributeConverter::create in order to use Enum::toString as the enum identifier
+ *
+ * <p>
+ * Use EnumAttributeConverter::createWithNameAsKeys in order to use Enum::name as the enum identifier
+ *
+ * <p>
  * This can be created via {@link #create(Class)}.
  */
 @SdkInternalApi
@@ -41,23 +48,30 @@ public class EnumAttributeConverter<T extends Enum<T>> implements AttributeConve
     private final Class<T> enumClass;
     private final Map<String, T> enumValueMap;
 
-    private EnumAttributeConverter(Class<T> enumClass) {
+    private final Function<T, String> keyExtractor;
+
+    private EnumAttributeConverter(Class<T> enumClass, Function<T, String> keyExtractor) {
         this.enumClass = enumClass;
+        this.keyExtractor = keyExtractor;
 
         Map<String, T> mutableEnumValueMap = new LinkedHashMap<>();
         Arrays.stream(enumClass.getEnumConstants())
-              .forEach(enumConstant -> mutableEnumValueMap.put(enumConstant.toString(), enumConstant));
+              .forEach(enumConstant -> mutableEnumValueMap.put(keyExtractor.apply(enumConstant), enumConstant));
 
         this.enumValueMap = Collections.unmodifiableMap(mutableEnumValueMap);
     }
 
     public static <T extends Enum<T>> EnumAttributeConverter<T> create(Class<T> enumClass) {
-        return new EnumAttributeConverter<>(enumClass);
+        return new EnumAttributeConverter<>(enumClass, Enum::toString);
+    }
+
+    public static <T extends Enum<T>> EnumAttributeConverter<T> createWithNameAsKeys(Class<T> enumClass) {
+        return new EnumAttributeConverter<>(enumClass, Enum::name);
     }
 
     @Override
     public AttributeValue transformFrom(T input) {
-        return AttributeValue.builder().s(input.toString()).build();
+        return AttributeValue.builder().s(keyExtractor.apply(input)).build();
     }
 
     @Override

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

@@ -0,0 +1,90 @@
+/*
+ * 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.converters.attribute;
+
+import org.junit.jupiter.api.Test;
+import software.amazon.awssdk.enhanced.dynamodb.internal.converter.attribute.EnumAttributeConverter;
+import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class EnumAttributeConverterTest {
+
+    @Test
+    public void transformFromDefault_returnsToString() {
+        EnumAttributeConverter<Animal> animalConverter = EnumAttributeConverter.create(Animal.class);
+        AttributeValue attribute = animalConverter.transformFrom(Animal.CAT);
+
+        assertThat(attribute.s()).isEqualTo("I am a Cat!");
+    }
+
+    @Test
+    public void transformToDefault_returnsEnum() {
+        EnumAttributeConverter<Animal> animalConverter = EnumAttributeConverter.create(Animal.class);
+
+        Animal dog = animalConverter.transformTo(AttributeValue.fromS("I am a Dog!"));
+
+        assertThat(dog).isEqualTo(Animal.DOG);
+    }
+
+    @Test
+    public void transformFromWithNames_returnsName() {
+        EnumAttributeConverter<Person> personConverter = EnumAttributeConverter.createWithNameAsKeys(Person.class);
+        AttributeValue attribute = personConverter.transformFrom(Person.JANE);
+
+        assertThat(attribute.s()).isEqualTo("JANE");
+
+        assertThat(Person.JANE.toString()).isEqualTo("I am a cool person");
+    }
+
+    @Test
+    public void transformToWithNames_returnsEnum() {
+        EnumAttributeConverter<Person> personConverter = EnumAttributeConverter.createWithNameAsKeys(Person.class);
+
+        Person john = personConverter.transformTo(AttributeValue.fromS("JOHN"));
+
+        assertThat(Person.JOHN.toString()).isEqualTo("I am a cool person");
+
+        assertThat(john).isEqualTo(Person.JOHN);
+    }
+
+    private static enum Animal {
+        DOG,
+        CAT;
+
+        @Override
+        public String toString() {
+            switch (this) {
+                case DOG:
+                    return "I am a Dog!";
+                case CAT:
+                    return "I am a Cat!";
+                default:
+                    return null;
+            }
+        }
+    }
+
+    private static enum Person {
+        JOHN,
+        JANE;
+
+        @Override
+        public String toString() {
+            return "I am a cool person";
+        }
+    }
+}