Batch Load Using DynamoDB Mapper (Guide w/ Code Examples)

BatchGetItem reads several known full primary keys, including keys from different partitions. Handle UnprocessedKeys separately from returned items and do not assume response order matches request order.

DynamoDBMapper belongs to AWS SDK for Java 1.x and cannot be constructed with a 2.x DynamoDbClient. The example below shows the SDK 2.x low-level equivalent. For mapped domain objects, use the DynamoDB Enhanced Client.

This example uses Java 17+ and the software.amazon.awssdk:dynamodb SDK 2.x dependency. Configure an AWS Region and credentials through your usual AWS profile or runtime role. The Orders table has String keys pk and sk; adapt the table and keys to your schema.

import java.util.*;
import software.amazon.awssdk.services.dynamodb.DynamoDbClient;
import software.amazon.awssdk.services.dynamodb.model.*;

public class Example {
    static AttributeValue s(String value) { return AttributeValue.builder().s(value).build(); }
    static Map<String, AttributeValue> key(String order) {
        return Map.of("pk", s("CUSTOMER#123"), "sk", s(order));
    }

    public static void main(String[] args) throws InterruptedException {
        try (DynamoDbClient ddb = DynamoDbClient.create()) {
            Map<String, KeysAndAttributes> pending = Map.of("Orders",
                KeysAndAttributes.builder().keys(key("ORDER#001"), key("ORDER#002")).build());
            for (int attempt = 0; !pending.isEmpty(); attempt++) {
                if (attempt == 8) throw new IllegalStateException("Unprocessed keys: " + pending);
                if (attempt > 0) Thread.sleep((long) (Math.random() * Math.min(5000L, 100L << attempt)));
                BatchGetItemResponse response = ddb.batchGetItem(BatchGetItemRequest.builder()
                    .requestItems(pending).build());
                response.responses().getOrDefault("Orders", List.of()).forEach(System.out::println);
                pending = response.unprocessedKeys();
            }
        }
    }
}

Use at most 100 distinct keys per request. Size limits or throttling can produce a partial response even below that count. A nonexistent item is omitted, not returned as an error.

Reference: AWS BatchGetItem API. For related access patterns, see DynamoDB query examples.