aws · musketyr · Apr 1, 2020 · Apr 1, 2020 · Apr 2, 2020
@@ -1,4 +1,9 @@
 # __2.11.7__ __2020-04-01__
+
+## __Amazon DynamoDB Enhanced Client [Preview]__
+  - ### Features
+    - Added support for exposing attribute accessor and converters. 
+
 ## __AWS IoT__
   - ### Features
     - This release introduces Dimensions for AWS IoT Device Defender. Dimensions can be used in Security Profiles to collect and monitor fine-grained metrics.
@@ -11,6 +16,7 @@
   - ### Features
     - Updated service endpoint metadata.
 
+
 # __2.11.6__ __2020-03-31__
 ## __AWS Elemental MediaStore__
   - ### Features

@@ -0,0 +1,66 @@
+/*
+ * 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;
+
+import java.util.function.BiConsumer;
+import java.util.function.Function;
+import software.amazon.awssdk.annotations.SdkPublicApi;
+import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
+
+/**
+ * Represents an attribute of a table model.
+ *
+ * @param <T> type of the model.
+ * @param <R> type type of the attribute.
+ */
+@SdkPublicApi
+public interface Attribute<T, R> {
+
+    /**
+     * Returns the name of the attribute.
+     *
+     * @return the name of the attribute.
+     */
+    String attributeName();
+
+    /**
+     * Returns the {@link AttributeType} of the attribute which helps with converting the values.
+     *
+     * @return the {@link AttributeType} of the attribute which helps with converting the values.
+     */
+    AttributeType<R> attributeType();
+
+    /**
+     * Returns the function which can be used to obtain the attribute value as {@link AttributeValue} from given object.
+     *
+     * @return the function which can be used to obtain the attribute value as {@link AttributeValue} from given object.
+     */
+    Function<T, AttributeValue> attributeGetterMethod();
+
+    /**
+     * Returns the consumer which can be used to set the attribute value as {@link AttributeValue} from given object.
+     *
+     * @return the consumer which can be used to set the attribute value as {@link AttributeValue} from given object.
+     */
+    BiConsumer<T, AttributeValue> updateItemMethod();
+
+    /**
+     * Returns the {@link TableMetadata} of the parent model.
+     *
+     * @return the {@link TableMetadata} of the parent model.
+     */
+    TableMetadata tableMetadata();
+}
@@ -0,0 +1,48 @@
+/*
+ * 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;
+
+import software.amazon.awssdk.annotations.SdkPublicApi;
+import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
+
+/**
+ * Attribute type helps to convert attribute values from and to their {@link AttributeValue} representation.
+ * @param <T> the type of the attribute.
+ */
+@SdkPublicApi
+public interface AttributeType<T> {
+
+    /**
+     * Converts an object representing value of a attribute into {@link AttributeValue}.
+     *
+     * @param object an object to be converted.
+     * @return {@link AttributeValue} representation of the object.
+     */
+    AttributeValue objectToAttributeValue(T object);
+
+    /**
+     * Converts an {@link AttributeValue} to the value expected by the attribute.
+     * @param attributeValue  {@link AttributeValue} to be converted.
+     * @return the object representation of the {@link AttributeValue}.
+     */
+    T attributeValueToObject(AttributeValue attributeValue);
+
+    /**
+     * Returns the {@link AttributeValueType} representation of the Java class of the attribute.
+     * @return the {@link AttributeValueType} representation of the Java class of the attribute.
+     */
+    AttributeValueType attributeValueType();
+}
@@ -115,4 +115,12 @@ static <T> BeanTableSchema<T> fromBean(Class<T> beanClass) {
      * @return The {@link EnhancedType} of the modelled item this TableSchema maps to.
      */
     EnhancedType<T> itemType();
+
+    /**
+     * Returns an attribute accessor from the modelled object.
+     *
+     * @param key The attribute name describing which attribute to obtain.
+     * @return A single {@link Attribute} for accessing the requested modelled attribute in the model object.
+     */
+    Attribute<T, ?> attribute(String key);
 }
@@ -22,32 +22,32 @@
 import java.util.function.Consumer;
 import java.util.function.Function;
 import software.amazon.awssdk.annotations.SdkInternalApi;
-import software.amazon.awssdk.enhanced.dynamodb.AttributeValueType;
+import software.amazon.awssdk.enhanced.dynamodb.AttributeType;
 import software.amazon.awssdk.enhanced.dynamodb.mapper.StaticAttribute;
 import software.amazon.awssdk.enhanced.dynamodb.mapper.StaticTableMetadata;
 import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
 
 @SdkInternalApi
-public final class ResolvedStaticAttribute<T> {
+public final class ResolvedStaticAttribute<T, R> implements software.amazon.awssdk.enhanced.dynamodb.Attribute<T, R> {
     private final String attributeName;
     private final Function<T, AttributeValue> getAttributeMethod;
     private final BiConsumer<T, AttributeValue> updateItemMethod;
     private final StaticTableMetadata tableMetadata;
-    private final AttributeValueType attributeValueType;
+    private final AttributeType<R> attributeType;
 
     private ResolvedStaticAttribute(String attributeName,
                                     Function<T, AttributeValue> getAttributeMethod,
                                     BiConsumer<T, AttributeValue> updateItemMethod,
                                     StaticTableMetadata tableMetadata,
-                                    AttributeValueType attributeValueType) {
+                                    AttributeType<R> attributeType) {
         this.attributeName = attributeName;
         this.getAttributeMethod = getAttributeMethod;
         this.updateItemMethod = updateItemMethod;
         this.tableMetadata = tableMetadata;
-        this.attributeValueType = attributeValueType;
+        this.attributeType = attributeType;
     }
 
-    public static <T, R> ResolvedStaticAttribute<T> create(StaticAttribute<T, R> staticAttribute,
+    public static <T, R> ResolvedStaticAttribute<T, R> create(StaticAttribute<T, R> staticAttribute,
                                                            AttributeType<R> attributeType) {
         Function<T, AttributeValue> getAttributeValueWithTransform = item -> {
             R value = staticAttribute.getter().apply(item);
@@ -78,21 +78,21 @@ public static <T, R> ResolvedStaticAttribute<T> create(StaticAttribute<T, R> sta
                                              getAttributeValueWithTransform,
                                              updateItemWithTransform,
                                              tableMetadataBuilder.build(),
-                                             attributeType.attributeValueType());
+                                             attributeType);
     }
 
     /**
      * Return a transformed copy of this attribute that knows how to get/set from a different type of object given a
      * function that can convert the containing object itself. It does this by modifying the get/set functions of
-     * type T to type R given a transformation function F(T) = R.
+     * type T to type S given a transformation function F(T) = S.
      * @param transform A function that converts the object storing the attribute from the source type to the
      *                  destination type.
      * @param createComponent A consumer to create a new instance of the component object when required. A null value
      *                       will bypass this logic.
-     * @param <R> The type being transformed to.
-     * @return A new Attribute that be contained by an object of type R.
+     * @param <S> The type being transformed to.
+     * @return A new Attribute that be contained by an object of type S.
      */
-    public <R> ResolvedStaticAttribute<R> transform(Function<R, T> transform, Consumer<R> createComponent) {
+    public <S> ResolvedStaticAttribute<S, R> transform(Function<S, T> transform, Consumer<S> createComponent) {
         return new ResolvedStaticAttribute<>(
             attributeName,
             item -> {
@@ -110,21 +110,30 @@ public <R> ResolvedStaticAttribute<R> transform(Function<R, T> transform, Consum
                 updateItemMethod.accept(transform.apply(item), value);
             },
             tableMetadata,
-            attributeValueType);
+            attributeType);
     }
 
+    @Override
     public String attributeName() {
         return attributeName;
     }
 
+    @Override
+    public AttributeType<R> attributeType() {
+        return attributeType;
+    }
+
+    @Override
     public Function<T, AttributeValue> attributeGetterMethod() {
         return getAttributeMethod;
     }
 
+    @Override
     public BiConsumer<T, AttributeValue> updateItemMethod() {
         return updateItemMethod;
     }
 
+    @Override
     public StaticTableMetadata tableMetadata() {
         return tableMetadata;
     }

@@ -17,6 +17,7 @@
 
 import software.amazon.awssdk.annotations.SdkInternalApi;
 import software.amazon.awssdk.enhanced.dynamodb.AttributeConverter;
+import software.amazon.awssdk.enhanced.dynamodb.AttributeType;
 import software.amazon.awssdk.enhanced.dynamodb.AttributeValueType;
 import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
 

@@ -37,6 +37,7 @@
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 import software.amazon.awssdk.annotations.SdkPublicApi;
+import software.amazon.awssdk.enhanced.dynamodb.Attribute;
 import software.amazon.awssdk.enhanced.dynamodb.AttributeConverter;
 import software.amazon.awssdk.enhanced.dynamodb.AttributeConverterProvider;
 import software.amazon.awssdk.enhanced.dynamodb.DynamoDbEnhancedClient;
@@ -172,6 +173,11 @@ public EnhancedType<T> itemType() {
         return wrappedTableSchema.itemType();
     }
 
+    @Override
+    public Attribute<T, ?> attribute(String key) {
+        return wrappedTableSchema.attribute(key);
+    }
+
     private static <T> StaticTableSchema<T> createStaticTableSchema(Class<T> beanClass) {
         DynamoDbBean dynamoDbBean = beanClass.getAnnotation(DynamoDbBean.class);
 

@@ -150,7 +150,7 @@ public Builder<T, R> toBuilder() {
     }
 
 
-    ResolvedStaticAttribute<T> resolve(AttributeConverterProvider attributeConverterProvider) {
+    ResolvedStaticAttribute<T, R> resolve(AttributeConverterProvider attributeConverterProvider) {
         return ResolvedStaticAttribute.create(this,
                                               StaticAttributeType.create(converterFrom(attributeConverterProvider)));
     }