Add Extension for @DynamoDBGeneratedUuid for EnhancedDynamoDB client

.changes/next-release/feature-AWSDynamoDBEnhancedClient-faf3991.json

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+{
+    "type": "feature",
+    "category": "AWS DynamoDB Enhanced Client",
+    "contributor": "",
+    "description": "Added support for `@DynamoDBAutoGeneratedUUID` to facilitate the automatic updating of DynamoDB attributes with random UUID."
+}

.changes/next-release/feature-AWSSDKforJavav2-5500cf7.json

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+{
+    "type": "feature",
+    "category": "AWS SDK for Java v2",
+    "contributor": "",
+    "description": "Added support for `@DynamoDBAutoGeneratedUUID` to facilitate the automatic updating of DynamoDB attributes with random UUID."
+}

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

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+/*
+ * 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.extensions;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.UUID;
+import java.util.function.Consumer;
+import software.amazon.awssdk.annotations.SdkPublicApi;
+import software.amazon.awssdk.annotations.ThreadSafe;
+import software.amazon.awssdk.enhanced.dynamodb.AttributeValueType;
+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.mapper.StaticAttributeTag;
+import software.amazon.awssdk.enhanced.dynamodb.mapper.StaticTableMetadata;
+import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.DynamoDbUpdateBehavior;
+import software.amazon.awssdk.services.dynamodb.model.AttributeValue;
+import software.amazon.awssdk.utils.Validate;
+
+
+/**
+ * This extension facilitates the automatic generation of a unique UUID (Universally Unique Identifier) for a specified attribute
+ * every time a new record is written to the database. The generated UUID is obtained using the
+ * {@link java.util.UUID#randomUUID()} method.
+ * <p>
+ * This extension is not loaded by default when you instantiate a
+ * {@link software.amazon.awssdk.enhanced.dynamodb.DynamoDbEnhancedClient}. Therefore, you need to specify it in a custom
+ * extension when creating the enhanced client.
+ * <p>
+ * Example to add AutoGeneratedUuidExtension along with default extensions is
+ * {@snippet :
+ * DynamoDbEnhancedClient.builder().extensions(Stream.concat(ExtensionResolver.defaultExtensions().stream(),
+ * Stream.of(AutoGeneratedUuidExtension.create())).collect(Collectors.toList())).build();
+ *}
+ * </p>
+ * <p>
+ * Example to just add AutoGeneratedUuidExtension without default extensions is
+ * {@snippet :
+ *             DynamoDbEnhancedClient.builder().extensions(AutoGeneratedUuidExtension.create()).build();
+ *}
+ * </p>
+ * <p>
+ * To utilize the auto-generated UUID feature, first, create a field in your model that will store the UUID for the attribute.
+ * This class field must be of type {@link java.lang.String}, and you need to tag it as the autoGeneratedUuidAttribute. If you are
+ * using the {@link software.amazon.awssdk.enhanced.dynamodb.mapper.BeanTableSchema}, then you should use the
+ * {@link software.amazon.awssdk.enhanced.dynamodb.extensions.annotations.DynamoDbAutoGeneratedUuid} annotation. If you are using
+ * the {@link software.amazon.awssdk.enhanced.dynamodb.mapper.StaticTableSchema}, then you should use the
+ * {@link
+ * software.amazon.awssdk.enhanced.dynamodb.extensions.AutoGeneratedUuidExtension.AttributeTags#autoGeneratedUuidAttribute()}
+ * static attribute tag.
+ * </p>
+ * <p>
+ * Every time a new record is successfully put into the database, the specified attribute will be automatically populated with a
+ * unique UUID generated using {@link java.util.UUID#randomUUID()}. If the UUID needs to be created only for `putItem` and should
+ * not be generated for an `updateItem`, then
+ * {@link software.amazon.awssdk.enhanced.dynamodb.mapper.UpdateBehavior#WRITE_IF_NOT_EXISTS} must be along with
+ * {@link DynamoDbUpdateBehavior}
+ *
+ * </p>
+ */
+@SdkPublicApi
+@ThreadSafe
+public final class AutoGeneratedUuidExtension implements DynamoDbEnhancedClientExtension {
+    private static final String CUSTOM_METADATA_KEY =
+        "software.amazon.awssdk.enhanced.dynamodb.extensions.AutoGeneratedUuidExtension:AutoGeneratedUuidAttribute";
+    private static final AutoGeneratedUuidAttribute AUTO_GENERATED_UUID_ATTRIBUTE = new AutoGeneratedUuidAttribute();
+
+    private AutoGeneratedUuidExtension() {
+    }
+
+    /**
+     * @return an Instance of {@link AutoGeneratedUuidExtension}
+     */
+    public static AutoGeneratedUuidExtension create() {
+        return new AutoGeneratedUuidExtension();
+    }
+
+    /**
+     * Modifies the WriteModification UUID string with the attribute updated with the extension.
+     *
+     * @param context The {@link DynamoDbExtensionContext.BeforeWrite} context containing the state of the execution.
+     * @return WriteModification String updated with attribute updated with Extension.
+     */
+    @Override
+    public WriteModification beforeWrite(DynamoDbExtensionContext.BeforeWrite context) {
+
+
+        Collection<String> customMetadataObject = context.tableMetadata()
+                                                         .customMetadataObject(CUSTOM_METADATA_KEY, Collection.class)
+                                                         .orElse(null);
+
+        if (customMetadataObject == null) {
+            return WriteModification.builder().build();
+        }
+
+        Map<String, AttributeValue> itemToTransform = new HashMap<>(context.items());
+        customMetadataObject.forEach(key -> insertUuidInItemToTransform(itemToTransform, key));
+        return WriteModification.builder()
+                                .transformedItem(Collections.unmodifiableMap(itemToTransform))
+                                .build();
+    }
+
+    private void insertUuidInItemToTransform(Map<String, AttributeValue> itemToTransform,
+                                             String key) {
+        itemToTransform.put(key, AttributeValue.builder().s(UUID.randomUUID().toString()).build());
+    }
+
+    public static final class AttributeTags {
+
+        private AttributeTags() {
+        }
+
+        /**
+         * Tags which indicate that the given attribute is supported wih Auto Generated UUID Record Extension.
+         *
+         * @return Tag name for AutoGenerated UUID Records
+         */
+        public static StaticAttributeTag autoGeneratedUuidAttribute() {
+            return AUTO_GENERATED_UUID_ATTRIBUTE;
+        }
+    }
+
+    private static class AutoGeneratedUuidAttribute implements StaticAttributeTag {
+
+        @Override
+        public <R> void validateType(String attributeName, EnhancedType<R> type,
+                                     AttributeValueType attributeValueType) {
+
+            Validate.notNull(type, "type is null");
+            Validate.notNull(type.rawClass(), "rawClass is null");
+            Validate.notNull(attributeValueType, "attributeValueType is null");
+
+            if (!type.rawClass().equals(String.class)) {
+                throw new IllegalArgumentException(String.format(
+                    "Attribute '%s' of Class type %s is not a suitable Java Class type to be used as a Auto Generated "
+                    + "Uuid attribute. Only String Class type is supported.", attributeName, type.rawClass()));
+            }
+        }
+
+        @Override
+        public Consumer<StaticTableMetadata.Builder> modifyMetadata(String attributeName,
+                                                                    AttributeValueType attributeValueType) {
+            return metadata -> metadata.addCustomMetadataObject(CUSTOM_METADATA_KEY, Collections.singleton(attributeName))
+                                       .markAttributeAsKey(attributeName, attributeValueType);
+        }
+    }
+}

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

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+/*
+ * 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.extensions.annotations;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import java.util.UUID;
+import software.amazon.awssdk.annotations.SdkPublicApi;
+import software.amazon.awssdk.enhanced.dynamodb.internal.extensions.AutoGeneratedUuidTag;
+import software.amazon.awssdk.enhanced.dynamodb.mapper.annotations.BeanTableSchemaAttributeTag;
+
+/**
+ * Denotes this attribute as recording the auto generated UUID string for the record. Every time a record with this
+ * attribute is written to the database it will update the attribute with a {@link UUID#randomUUID} string.
+ */
+@SdkPublicApi
+@Target(ElementType.METHOD)
+@Retention(RetentionPolicy.RUNTIME)
+@BeanTableSchemaAttributeTag(AutoGeneratedUuidTag.class)
+public @interface DynamoDbAutoGeneratedUuid {
+}

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

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+/*
+ * 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.extensions;
+
+import software.amazon.awssdk.annotations.SdkInternalApi;
+import software.amazon.awssdk.enhanced.dynamodb.extensions.AutoGeneratedUuidExtension;
+import software.amazon.awssdk.enhanced.dynamodb.extensions.annotations.DynamoDbAutoGeneratedUuid;
+import software.amazon.awssdk.enhanced.dynamodb.mapper.StaticAttributeTag;
+
+@SdkInternalApi
+public final class AutoGeneratedUuidTag {
+
+    private AutoGeneratedUuidTag() {
+    }
+
+    public static StaticAttributeTag attributeTagFor(DynamoDbAutoGeneratedUuid annotation) {
+        return AutoGeneratedUuidExtension.AttributeTags.autoGeneratedUuidAttribute();
+    }
+
+}