zhongwei/gh-giuseppe-trisciuoglio-developer-kit

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AWS SDK for Java 2.x - Amazon DynamoDB

When to Use

Use this skill when:

Creating, updating, or deleting DynamoDB tables
Performing CRUD operations on DynamoDB items
Querying or scanning tables
Working with Global Secondary Indexes (GSI) or Local Secondary Indexes (LSI)
Implementing batch operations for efficiency
Using DynamoDB transactions
Integrating DynamoDB with Spring Boot applications
Working with DynamoDB Enhanced Client for type-safe operations

Dependencies

Add to pom.xml:

<!-- Low-level DynamoDB client -->
<dependency>
    <groupId>software.amazon.awssdk</groupId>
    <artifactId>dynamodb</artifactId>
</dependency>

<!-- Enhanced client (recommended) -->
<dependency>
    <groupId>software.amazon.awssdk</groupId>
    <artifactId>dynamodb-enhanced</artifactId>
</dependency>

Client Setup

Low-Level Client

import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.dynamodb.DynamoDbClient;

DynamoDbClient dynamoDb = DynamoDbClient.builder()
    .region(Region.US_EAST_1)
    .build();

Enhanced Client (Recommended)

import software.amazon.awssdk.enhanced.dynamodb.DynamoDbEnhancedClient;

DynamoDbEnhancedClient enhancedClient = DynamoDbEnhancedClient.builder()
    .dynamoDbClient(dynamoDb)
    .build();

Entity Mapping

To define DynamoDB entities, use @DynamoDbBean annotation:

@DynamoDbBean
public class Customer {

    @DynamoDbPartitionKey
    private String customerId;

    @DynamoDbAttribute("customer_name")
    private String name;

    private String email;

    @DynamoDbSortKey
    private String orderId;

    // Getters and setters
}

For complex entity mapping with GSIs and custom converters, see Entity Mapping Reference.

CRUD Operations

Basic Operations

// Create or update item
DynamoDbTable<Customer> table = enhancedClient.table("Customers", TableSchema.fromBean(Customer.class));
table.putItem(customer);

// Get item
Customer result = table.getItem(Key.builder().partitionValue(customerId).build());

// Update item
return table.updateItem(customer);

// Delete item
table.deleteItem(Key.builder().partitionValue(customerId).build());

Composite Key Operations

// Get item with composite key
Order order = table.getItem(Key.builder()
    .partitionValue(customerId)
    .sortValue(orderId)
    .build());

Query Operations

Basic Query

import software.amazon.awssdk.enhanced.dynamodb.model.QueryConditional;

QueryConditional queryConditional = QueryConditional
    .keyEqualTo(Key.builder()
        .partitionValue(customerId)
        .build());

List<Order> orders = table.query(queryConditional).items().stream()
    .collect(Collectors.toList());

Advanced Query with Filters

import software.amazon.awssdk.enhanced.dynamodb.Expression;

Expression filter = Expression.builder()
    .expression("status = :pending")
    .putExpressionValue(":pending", AttributeValue.builder().s("PENDING").build())
    .build();

List<Order> pendingOrders = table.query(r -> r
    .queryConditional(queryConditional)
    .filterExpression(filter))
    .items().stream()
    .collect(Collectors.toList());

For detailed query patterns, see Advanced Operations Reference.

Scan Operations

// Scan all items
List<Customer> allCustomers = table.scan().items().stream()
    .collect(Collectors.toList());

// Scan with filter
Expression filter = Expression.builder()
    .expression("points >= :minPoints")
    .putExpressionValue(":minPoints", AttributeValue.builder().n("1000").build())
    .build();

List<Customer> vipCustomers = table.scan(r -> r.filterExpression(filter))
    .items().stream()
    .collect(Collectors.toList());

Batch Operations

Batch Get

import software.amazon.awssdk.enhanced.dynamodb.model.*;

List<Key> keys = customerIds.stream()
    .map(id -> Key.builder().partitionValue(id).build())
    .collect(Collectors.toList());

ReadBatch.Builder<Customer> batchBuilder = ReadBatch.builder(Customer.class)
    .mappedTableResource(table);

keys.forEach(batchBuilder::addGetItem);

BatchGetResultPageIterable result = enhancedClient.batchGetItem(r ->
    r.addReadBatch(batchBuilder.build()));

List<Customer> customers = result.resultsForTable(table).stream()
    .collect(Collectors.toList());

Batch Write

WriteBatch.Builder<Customer> batchBuilder = WriteBatch.builder(Customer.class)
    .mappedTableResource(table);

customers.forEach(batchBuilder::addPutItem);

enhancedClient.batchWriteItem(r -> r.addWriteBatch(batchBuilder.build()));

Transactions

Transactional Write

enhancedClient.transactWriteItems(r -> r
    .addPutItem(customerTable, customer)
    .addPutItem(orderTable, order));

Transactional Read

TransactGetItemsEnhancedRequest request = TransactGetItemsEnhancedRequest.builder()
    .addGetItem(customerTable, customerKey)
    .addGetItem(orderTable, orderKey)
    .build();

List<Document> results = enhancedClient.transactGetItems(request);

Spring Boot Integration

Configuration

@Configuration
public class DynamoDbConfiguration {

    @Bean
    public DynamoDbClient dynamoDbClient() {
        return DynamoDbClient.builder()
            .region(Region.US_EAST_1)
            .build();
    }

    @Bean
    public DynamoDbEnhancedClient dynamoDbEnhancedClient(DynamoDbClient dynamoDbClient) {
        return DynamoDbEnhancedClient.builder()
            .dynamoDbClient(dynamoDbClient)
            .build();
    }
}

Repository Pattern

@Repository
public class CustomerRepository {

    private final DynamoDbTable<Customer> customerTable;

    public CustomerRepository(DynamoDbEnhancedClient enhancedClient) {
        this.customerTable = enhancedClient.table("Customers", TableSchema.fromBean(Customer.class));
    }

    public void save(Customer customer) {
        customerTable.putItem(customer);
    }

    public Optional<Customer> findById(String customerId) {
        Key key = Key.builder().partitionValue(customerId).build();
        return Optional.ofNullable(customerTable.getItem(key));
    }
}

For comprehensive Spring Boot integration patterns, see Spring Boot Integration Reference.

Testing

Unit Testing with Mocks

@ExtendWith(MockitoExtension.class)
class CustomerServiceTest {

    @Mock
    private DynamoDbClient dynamoDbClient;

    @Mock
    private DynamoDbEnhancedClient enhancedClient;

    @Mock
    private DynamoDbTable<Customer> customerTable;

    @InjectMocks
    private CustomerService customerService;

    @Test
    void saveCustomer_ShouldReturnSavedCustomer() {
        // Arrange
        when(enhancedClient.table(anyString(), any(TableSchema.class)))
            .thenReturn(customerTable);

        Customer customer = new Customer("123", "John Doe", "john@example.com");

        // Act
        Customer result = customerService.saveCustomer(customer);

        // Assert
        assertNotNull(result);
        verify(customerTable).putItem(customer);
    }
}

Integration Testing with LocalStack

@Testcontainers
@SpringBootTest
class DynamoDbIntegrationTest {

    @Container
    static LocalStackContainer localstack = new LocalStackContainer(
        DockerImageName.parse("localstack/localstack:3.0"))
        .withServices(LocalStackContainer.Service.DYNAMODB);

    @DynamicPropertySource
    static void configureProperties(DynamicPropertyRegistry registry) {
        registry.add("aws.endpoint",
            () -> localstack.getEndpointOverride(LocalStackContainer.Service.DYNAMODB).toString());
    }

    @Autowired
    private DynamoDbEnhancedClient enhancedClient;

    @Test
    void testCustomerCRUDOperations() {
        // Test implementation
    }
}

For detailed testing strategies, see Testing Strategies.

Best Practices

Use Enhanced Client: Provides type-safe operations with less boilerplate
Design partition keys carefully: Distribute data evenly across partitions
Use composite keys: Leverage sort keys for efficient queries
Create GSIs strategically: Support different access patterns
Use batch operations: Reduce API calls for multiple items
Implement pagination: For large result sets use pagination
Use transactions: For operations that must be atomic
Avoid scans: Prefer queries with proper indexes
Handle conditional writes: Prevent race conditions
Use proper error handling: Handle exceptions like ProvisionedThroughputExceeded

Common Patterns

Conditional Operations

PutItemEnhancedRequest request = PutItemEnhancedRequest.builder(table)
    .item(customer)
    .conditionExpression("attribute_not_exists(customerId)")
    .build();

table.putItemWithRequestBuilder(request);

Pagination

ScanEnhancedRequest request = ScanEnhancedRequest.builder()
    .limit(100)
    .build();

PaginatedScanIterable<Customer> results = table.scan(request);
results.stream().forEach(page -> {
    // Process each page
});

Performance Considerations

Monitor read/write capacity units
Implement exponential backoff for retries
Use proper pagination for large datasets
Consider eventual consistency for reads
Use ReturnConsumedCapacity to monitor capacity usage

aws-sdk-java-v2-core - Core AWS SDK patterns
spring-data-jpa - Alternative data access patterns
unit-test-service-layer - Service testing patterns
unit-test-wiremock-rest-api - Testing external APIs

References

For detailed implementations, see the references folder:

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