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Comprehensive developer toolkit providing reusable skills for Java/Spring Boot, TypeScript/NestJS/React/Next.js, Python, PHP, AWS CloudFormation, AI/RAG, DevOps, and more.

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SKILL.mdplugins/developer-kit-java/skills/aws-sdk-java-v2-s3/

name:
aws-sdk-java-v2-s3
description:
Provides Amazon S3 patterns and examples using AWS SDK for Java 2.x. Use when working with S3 buckets, uploading/downloading objects, multipart uploads, presigned URLs, S3 Transfer Manager, object operations, or S3-specific configurations.
allowed-tools:
Read, Write, Edit, Bash, Glob, Grep

AWS SDK for Java 2.x - Amazon S3

Overview

Amazon S3 (Simple Storage Service) is object storage built to store and retrieve any amount of data from anywhere. This skill covers patterns for working with S3 using AWS SDK for Java 2.x, including bucket operations, object uploads/downloads, presigned URLs, multipart transfers, and Spring Boot integration.

When to Use

Use this skill when:

  • Creating, listing, or deleting S3 buckets with proper configuration
  • Uploading or downloading objects from S3 with metadata and encryption
  • Working with multipart uploads for large files (>100MB) with error handling
  • Generating presigned URLs for temporary access to S3 objects
  • Copying or moving objects between S3 buckets with metadata preservation
  • Setting object metadata, storage classes, and access controls
  • Implementing S3 Transfer Manager for optimized file transfers
  • Integrating S3 with Spring Boot applications for cloud storage
  • Setting up S3 event notifications for object lifecycle management
  • Managing bucket policies, CORS configuration, and access controls
  • Implementing retry mechanisms and error handling for S3 operations
  • Testing S3 integrations with LocalStack for development environments

Instructions

Follow these steps to work with Amazon S3:

  1. Add Dependencies - Include S3 and optional Transfer Manager dependencies
  2. Create Client - Instantiate S3Client with region and credentials
  3. Create Bucket - Use createBucket() with unique name and configuration
  4. Upload Objects - Use putObject() for small files or Transfer Manager for large files
  5. Download Objects - Use getObject() with ResponseInputStream
  6. Generate Presigned URLs - Use S3Presigner for temporary access
  7. Configure Permissions - Set bucket policies and access controls
  8. Set Lifecycle Rules - Configure object expiration and transitions

Dependencies

<dependency>
    <groupId>software.amazon.awssdk</groupId>
    <artifactId>s3</artifactId>
    <version>2.20.0</version> // Use the latest stable version
</dependency>

<!-- For S3 Transfer Manager -->
<dependency>
    <groupId>software.amazon.awssdk</groupId>
    <artifactId>s3-transfer-manager</artifactId>
    <version>2.20.0</version> // Use the latest stable version
</dependency>

<!-- For async operations -->
<dependency>
    <groupId>software.amazon.awssdk</groupId>
    <artifactId>netty-nio-client</artifactId>
    <version>2.20.0</version> // Use the latest stable version
</dependency>

Client Setup

Basic Synchronous Client

import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.s3.S3Client;

S3Client s3Client = S3Client.builder()
    .region(Region.US_EAST_1)
    .build();

Basic Asynchronous Client

import software.amazon.awssdk.services.s3.S3AsyncClient;

S3AsyncClient s3AsyncClient = S3AsyncClient.builder()
    .region(Region.US_EAST_1)
    .build();

Configured Client with Retry Logic

import software.amazon.awssdk.http.apache.ApacheHttpClient;
import software.amazon.awssdk.core.retry.RetryPolicy;
import software.amazon.awssdk.core.retry.backoff.ExponentialRetryBackoff;
import java.time.Duration;

S3Client s3Client = S3Client.builder()
    .region(Region.US_EAST_1)
    .httpClientBuilder(ApacheHttpClient.builder()
        .maxConnections(200)
        .connectionTimeout(Duration.ofSeconds(5)))
    .overrideConfiguration(b -> b
        .apiCallTimeout(Duration.ofSeconds(60))
        .apiCallAttemptTimeout(Duration.ofSeconds(30))
        .retryPolicy(RetryPolicy.builder()
            .numRetries(3)
            .retryBackoffStrategy(ExponentialRetryBackoff.builder()
                .baseDelay(Duration.ofSeconds(1))
                .maxBackoffTime(Duration.ofSeconds(30))
                .build())
            .build()))
    .build();

Basic Bucket Operations

Create Bucket

import software.amazon.awssdk.services.s3.model.*;
import java.util.concurrent.CompletableFuture;

public void createBucket(S3Client s3Client, String bucketName) {
    try {
        CreateBucketRequest request = CreateBucketRequest.builder()
            .bucket(bucketName)
            .build();

        s3Client.createBucket(request);

        // Wait until bucket is ready
        HeadBucketRequest waitRequest = HeadBucketRequest.builder()
            .bucket(bucketName)
            .build();

        s3Client.waiter().waitUntilBucketExists(waitRequest);
        System.out.println("Bucket created successfully: " + bucketName);

    } catch (S3Exception e) {
        System.err.println("Error creating bucket: " + e.awsErrorDetails().errorMessage());
        throw e;
    }
}

List All Buckets

public List<String> listAllBuckets(S3Client s3Client) {
    ListBucketsResponse response = s3Client.listBuckets();

    return response.buckets().stream()
        .map(Bucket::name)
        .collect(Collectors.toList());
}

Check if Bucket Exists

public boolean bucketExists(S3Client s3Client, String bucketName) {
    try {
        HeadBucketRequest request = HeadBucketRequest.builder()
            .bucket(bucketName)
            .build();

        s3Client.headBucket(request);
        return true;

    } catch (NoSuchBucketException e) {
        return false;
    }
}

Basic Object Operations

Upload File to S3

import software.amazon.awssdk.core.sync.RequestBody;
import java.nio.file.Paths;

public void uploadFile(S3Client s3Client, String bucketName, String key, String filePath) {
    PutObjectRequest request = PutObjectRequest.builder()
        .bucket(bucketName)
        .key(key)
        .build();

    s3Client.putObject(request, RequestBody.fromFile(Paths.get(filePath)));
    System.out.println("File uploaded: " + key);
}

Download File from S3

import software.amazon.awssdk.core.ResponseInputStream;
import software.amazon.awssdk.services.s3.model.GetObjectResponse;
import java.nio.file.Paths;

public void downloadFile(S3Client s3Client, String bucketName, String key, String destPath) {
    GetObjectRequest request = GetObjectRequest.builder()
        .bucket(bucketName)
        .key(key)
        .build();

    s3Client.getObject(request, Paths.get(destPath));
    System.out.println("File downloaded: " + destPath);
}

Get Object Metadata

public Map<String, String> getObjectMetadata(S3Client s3Client, String bucketName, String key) {
    HeadObjectRequest request = HeadObjectRequest.builder()
        .bucket(bucketName)
        .key(key)
        .build();

    HeadObjectResponse response = s3Client.headObject(request);
    return response.metadata();
}

Advanced Object Operations

Upload with Metadata and Encryption

public void uploadWithMetadata(S3Client s3Client, String bucketName, String key,
                                String filePath, Map<String, String> metadata) {
    PutObjectRequest request = PutObjectRequest.builder()
        .bucket(bucketName)
        .key(key)
        .metadata(metadata)
        .contentType("application/pdf")
        .serverSideEncryption(ServerSideEncryption.AES256)
        .storageClass(StorageClass.STANDARD_IA)
        .build();

    PutObjectResponse response = s3Client.putObject(request,
        RequestBody.fromFile(Paths.get(filePath)));

    System.out.println("Upload completed. ETag: " + response.eTag());
}

Copy Object Between Buckets

public void copyObject(S3Client s3Client, String sourceBucket, String sourceKey,
                       String destBucket, String destKey) {
    CopyObjectRequest request = CopyObjectRequest.builder()
        .sourceBucket(sourceBucket)
        .sourceKey(sourceKey)
        .destinationBucket(destBucket)
        .destinationKey(destKey)
        .build();

    s3Client.copyObject(request);
    System.out.println("Object copied: " + sourceKey + " -> " + destKey);
}

Delete Multiple Objects

public void deleteMultipleObjects(S3Client s3Client, String bucketName, List<String> keys) {
    List<ObjectIdentifier> objectIds = keys.stream()
        .map(key -> ObjectIdentifier.builder().key(key).build())
        .collect(Collectors.toList());

    Delete delete = Delete.builder()
        .objects(objectIds)
        .build();

    DeleteObjectsRequest request = DeleteObjectsRequest.builder()
        .bucket(bucketName)
        .delete(delete)
        .build();

    DeleteObjectsResponse response = s3Client.deleteObjects(request);

    response.deleted().forEach(deleted ->
        System.out.println("Deleted: " + deleted.key()));

    response.errors().forEach(error ->
        System.err.println("Failed to delete " + error.key() + ": " + error.message()));
}

Presigned URLs

Generate Download URL

import software.amazon.awssdk.services.s3.presigner.S3Presigner;
import software.amazon.awssdk.services.s3.presigner.model.*;
import java.time.Duration;

public String generateDownloadUrl(String bucketName, String key) {
    try (S3Presigner presigner = S3Presigner.builder()
            .region(Region.US_EAST_1)
            .build()) {

        GetObjectRequest getObjectRequest = GetObjectRequest.builder()
            .bucket(bucketName)
            .key(key)
            .build();

        GetObjectPresignRequest presignRequest = GetObjectPresignRequest.builder()
            .signatureDuration(Duration.ofMinutes(10))
            .getObjectRequest(getObjectRequest)
            .build();

        PresignedGetObjectRequest presignedRequest = presigner.presignGetObject(presignRequest);

        return presignedRequest.url().toString();
    }
}

Generate Upload URL

public String generateUploadUrl(String bucketName, String key) {
    try (S3Presigner presigner = S3Presigner.create()) {

        PutObjectRequest putObjectRequest = PutObjectRequest.builder()
            .bucket(bucketName)
            .key(key)
            .build();

        PutObjectPresignRequest presignRequest = PutObjectPresignRequest.builder()
            .signatureDuration(Duration.ofMinutes(5))
            .putObjectRequest(putObjectRequest)
            .build();

        PresignedPutObjectRequest presignedRequest = presigner.presignPutObject(presignRequest);

        return presignedRequest.url().toString();
    }
}

S3 Transfer Manager

Upload with Transfer Manager

import software.amazon.awssdk.transfer.s3.*;
import software.amazon.awssdk.transfer.s3.model.*;

public void uploadWithTransferManager(String bucketName, String key, String filePath) {
    try (S3TransferManager transferManager = S3TransferManager.create()) {

        UploadFileRequest uploadRequest = UploadFileRequest.builder()
            .putObjectRequest(req -> req
                .bucket(bucketName)
                .key(key))
            .source(Paths.get(filePath))
            .build();

        FileUpload upload = transferManager.uploadFile(uploadRequest);

        // Monitor progress
        upload.progressFuture().thenAccept(progress -> {
            System.out.println("Upload progress: " + progress.progressPercent() + "%");
        });

        CompletedFileUpload result = upload.completionFuture().join();

        System.out.println("Upload complete. ETag: " + result.response().eTag());
    }
}

Download with Transfer Manager

public void downloadWithTransferManager(String bucketName, String key, String destPath) {
    try (S3TransferManager transferManager = S3TransferManager.create()) {

        DownloadFileRequest downloadRequest = DownloadFileRequest.builder()
            .getObjectRequest(req -> req
                .bucket(bucketName)
                .key(key))
            .destination(Paths.get(destPath))
            .build();

        FileDownload download = transferManager.downloadFile(downloadRequest);

        CompletedFileDownload result = download.completionFuture().join();

        System.out.println("Download complete. Size: " + result.response().contentLength());
    }
}

Spring Boot Integration

Configuration Properties

import org.springframework.boot.context.properties.ConfigurationProperties;

@ConfigurationProperties(prefix = "aws.s3")
public class S3Properties {
    private String accessKey;
    private String secretKey;
    private String region = "us-east-1";
    private String endpoint;
    private String defaultBucket;
    private boolean asyncEnabled = false;
    private boolean transferManagerEnabled = true;

    // Getters and setters
    public String getAccessKey() { return accessKey; }
    public void setAccessKey(String accessKey) { this.accessKey = accessKey; }
    // ... other getters and setters
}

S3 Configuration Class

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import software.amazon.awssdk.auth.credentials.AwsBasicCredentials;
import software.amazon.awssdk.auth.credentials.StaticCredentialsProvider;
import software.amazon.awssdk.services.s3.S3Client;
import software.amazon.awssdk.services.s3.S3AsyncClient;
import software.amazon.awssdk.regions.Region;
import java.net.URI;

@Configuration
public class S3Configuration {

    private final S3Properties properties;

    public S3Configuration(S3Properties properties) {
        this.properties = properties;
    }

    @Bean
    public S3Client s3Client() {
        S3Client.Builder builder = S3Client.builder()
            .region(Region.of(properties.getRegion()));

        if (properties.getAccessKey() != null && properties.getSecretKey() != null) {
            builder.credentialsProvider(StaticCredentialsProvider.create(
                AwsBasicCredentials.create(
                    properties.getAccessKey(),
                    properties.getSecretKey())));
        }

        if (properties.getEndpoint() != null) {
            builder.endpointOverride(URI.create(properties.getEndpoint()));
        }

        return builder.build();
    }

    @Bean
    public S3AsyncClient s3AsyncClient() {
        S3AsyncClient.Builder builder = S3AsyncClient.builder()
            .region(Region.of(properties.getRegion()));

        if (properties.getAccessKey() != null && properties.getSecretKey() != null) {
            builder.credentialsProvider(StaticCredentialsProvider.create(
                AwsBasicCredentials.create(
                    properties.getAccessKey(),
                    properties.getSecretKey())));
        }

        if (properties.getEndpoint() != null) {
            builder.endpointOverride(URI.create(properties.getEndpoint()));
        }

        return builder.build();
    }

    @Bean
    public S3TransferManager s3TransferManager() {
        return S3TransferManager.builder()
            .s3Client(s3Client())
            .build();
    }
}

S3 Service

import org.springframework.stereotype.Service;
import software.amazon.awssdk.transfer.s3.S3TransferManager;
import software.amazon.awssdk.services.s3.model.*;
import java.nio.file.*;
import java.util.*;
import java.util.concurrent.CompletableFuture;

@Service
@RequiredArgsConstructor
public class S3Service {

    private final S3Client s3Client;
    private final S3AsyncClient s3AsyncClient;
    private final S3TransferManager transferManager;
    private final S3Properties properties;

    public CompletableFuture<Void> uploadFileAsync(String key, Path file) {
        PutObjectRequest request = PutObjectRequest.builder()
            .bucket(properties.getDefaultBucket())
            .key(key)
            .build();

        return CompletableFuture.runAsync(() -> {
            s3Client.putObject(request, RequestBody.fromFile(file));
        });
    }

    public CompletableFuture<byte[]> downloadFileAsync(String key) {
        GetObjectRequest request = GetObjectRequest.builder()
            .bucket(properties.getDefaultBucket())
            .key(key)
            .build();

        return CompletableFuture.supplyAsync(() -> {
            try (ResponseInputStream<GetObjectResponse> response = s3Client.getObject(request)) {
                return response.readAllBytes();
            } catch (IOException e) {
                throw new RuntimeException("Failed to read S3 object", e);
            }
        });
    }

    public CompletableFuture<String> generatePresignedUrl(String key, Duration duration) {
        return CompletableFuture.supplyAsync(() -> {
            try (S3Presigner presigner = S3Presigner.builder()
                    .region(Region.of(properties.getRegion()))
                    .build()) {

                GetObjectRequest getRequest = GetObjectRequest.builder()
                    .bucket(properties.getDefaultBucket())
                    .key(key)
                    .build();

                GetObjectPresignRequest presignRequest = GetObjectPresignRequest.builder()
                    .signatureDuration(duration)
                    .getObjectRequest(getRequest)
                    .build();

                return presigner.presignGetObject(presignRequest).url().toString();
            }
        });
    }

    public Flux<S3Object> listObjects(String prefix) {
        ListObjectsV2Request request = ListObjectsV2Request.builder()
            .bucket(properties.getDefaultBucket())
            .prefix(prefix)
            .build();

        return Flux.create(sink -> {
            s3Client.listObjectsV2Paginator(request)
                .contents()
                .forEach(sink::next);
            sink.complete();
        });
    }
}

Examples

Basic File Upload Example

public class S3UploadExample {
    public static void main(String[] args) {
        // Initialize client
        S3Client s3Client = S3Client.builder()
            .region(Region.US_EAST_1)
            .build();

        String bucketName = "my-example-bucket";
        String filePath = "document.pdf";
        String key = "uploads/document.pdf";

        // Create bucket if it doesn't exist
        if (!bucketExists(s3Client, bucketName)) {
            createBucket(s3Client, bucketName);
        }

        // Upload file
        Map<String, String> metadata = Map.of(
            "author", "John Doe",
            "content-type", "application/pdf",
            "upload-date", java.time.LocalDate.now().toString()
        );

        uploadWithMetadata(s3Client, bucketName, key, filePath, metadata);

        // Generate presigned URL
        String downloadUrl = generateDownloadUrl(bucketName, key);
        System.out.println("Download URL: " + downloadUrl);

        // Close client
        s3Client.close();
    }
}

Batch File Processing Example

import java.nio.file.*;
import java.util.stream.*;

public class S3BatchProcessing {
    public void processDirectoryUpload(S3Client s3Client, String bucketName, String directoryPath) {
        try (Stream<Path> paths = Files.walk(Paths.get(directoryPath))) {
            List<CompletableFuture<Void>> futures = paths
                .filter(Files::isRegularFile)
                .map(path -> {
                    String key = bucketName + "/" + path.getFileName().toString();
                    return CompletableFuture.runAsync(() -> {
                        uploadFile(s3Client, bucketName, key, path.toString());
                    });
                })
                .collect(Collectors.toList());

            // Wait for all uploads to complete
            CompletableFuture.allOf(
                futures.toArray(new CompletableFuture[0])
            ).join();

            System.out.println("All files uploaded successfully");
        } catch (IOException e) {
            throw new RuntimeException("Failed to process directory", e);
        }
    }
}

Best Practices

Performance Optimization

  1. Use S3 Transfer Manager: Automatically handles multipart uploads, parallel transfers, and progress tracking for files >100MB
  2. Reuse S3 Client: Clients are thread-safe and should be reused throughout the application lifecycle
  3. Enable async operations: Use S3AsyncClient for I/O-bound operations to improve throughput
  4. Configure proper timeouts: Set appropriate timeouts for large file operations
  5. Use connection pooling: Configure HTTP client for optimal connection management

Security Considerations

  1. Use temporary credentials: Always use IAM roles or AWS STS for short-lived access tokens
  2. Enable server-side encryption: Use AES-256 or AWS KMS for sensitive data
  3. Implement access controls: Use bucket policies and IAM roles instead of access keys in production
  4. Validate object metadata: Sanitize user-provided metadata to prevent header injection
  5. Use presigned URLs: Avoid exposing credentials by using temporary access URLs

Error Handling

  1. Implement retry logic: Network operations should have exponential backoff retry strategies
  2. Handle throttling: Implement proper handling of 429 Too Many Requests responses
  3. Validate object existence: Check if objects exist before operations that require them
  4. Clean up failed operations: Abort multipart uploads that fail
  5. Log appropriately: Log successful operations and errors for monitoring

Cost Optimization

  1. Use appropriate storage classes: Choose STANDARD, STANDARD_IA, INTELLIGENT_TIERING based on access patterns
  2. Implement lifecycle policies: Automatically transition or expire objects
  3. Enable object versioning: For important data that needs retention
  4. Monitor usage: Track data transfer and storage costs
  5. Minimize API calls: Use batch operations when possible

Constraints and Limitations

  • File size limits: Single PUT operations limited to 5GB; use multipart uploads for larger files
  • Batch operations: Maximum 1000 objects per DeleteObjects operation
  • Metadata size: User-defined metadata limited to 2KB
  • Concurrent transfers: Transfer Manager handles up to 100 concurrent transfers by default
  • Region consistency: Cross-region operations may incur additional costs and latency
  • S3 eventual consistency: New objects might not be immediately visible after upload

References

For more detailed information, see:

  • AWS S3 Object Operations Reference
  • S3 Transfer Manager Patterns
  • Spring Boot Integration Guide
  • AWS S3 Developer Guide
  • AWS SDK for Java 2.x S3 API

Related Skills

  • aws-sdk-java-v2-core - Core AWS SDK patterns and configuration
  • spring-boot-dependency-injection - Spring dependency injection patterns
  • unit-test-service-layer - Testing service layer patterns
  • unit-test-wiremock-rest-api - Testing external API integrations

Constraints and Warnings

  • Object Size: Single PUT limited to 5GB; use multipart uploads for larger files
  • Bucket Names: Must be globally unique across all AWS accounts
  • Object Immutability: Objects cannot be modified; must be replaced entirely
  • Eventual Consistency: List operations may have slight delays after uploads
  • Request Rates: S3 supports high request rates but has throttling limits
  • Storage Classes: Some storage classes have minimum duration requirements
  • Presigned URLs: Maximum expiration time is 7 days
  • Multipart Uploads: Parts must be at least 5MB except last part
  • Delete Markers: Versioning creates delete markers instead of actual deletion
  • Cross-Region: Cross-region replication incurs data transfer costs

plugins

developer-kit-java

skills

aws-sdk-java-v2-s3

SKILL.md

README.md

tile.json