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AWS SDK Java V2 S3 Agent Skill

by giuseppe-trisciuoglio

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.

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one command, takes just this skill from the repository 
npx skills add https://github.com/giuseppe-trisciuoglio/developer-kit --skill aws-sdk-java-v2-s3

The instruction itself

24 sections, as written by the author

AWS SDK for Java 2.x - Amazon S3

Overview

Provides patterns for S3 operations: bucket management, object upload/download with multipart support, presigned URLs, S3 Transfer Manager, and S3-specific configurations using AWS SDK for Java 2.x.

When to Use

  • 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

Quick Reference

| Operation | Method | Notes |

|-----------|--------|-------|

| Create bucket | createBucket() | Wait with waiter().waitUntilBucketExists() |

| Upload object | putObject() | Use RequestBody.fromFile() |

| Download object | getObject() | Streams to file or memory |

| Delete objects | deleteObjects() | Batch up to 1000 keys |

| Presigned URL | presigner.presignGetObject() | Max 7 days expiration |

Storage Classes

| Class | Use Case |

|-------|----------|

| STANDARD | Frequently accessed data |

| STANDARD_IA | Infrequently accessed data |

| GLACIER | Long-term archive |

| INTELLIGENT_TIERING | Automatic cost optimization |

Instructions

1. Add Dependencies

<dependency>
    <groupId>software.amazon.awssdk</groupId>
    <artifactId>s3</artifactId>
    <version>2.20.0</version>
</dependency>

<dependency>
    <groupId>software.amazon.awssdk</groupId>
    <artifactId>s3-transfer-manager</artifactId>
    <version>2.20.0</version>
</dependency>

2. Create S3 Client

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

// With retry logic
S3Client s3Client = S3Client.builder()
    .region(Region.US_EAST_1)
    .overrideConfiguration(b -> b
        .retryPolicy(RetryPolicy.builder()
            .numRetries(3)
            .build()))
    .build();

3. Create Bucket

CreateBucketRequest request = CreateBucketRequest.builder()
    .bucket(bucketName)
    .build();

s3Client.createBucket(request);

// Wait until ready
s3Client.waiter().waitUntilBucketExists(
    HeadBucketRequest.builder().bucket(bucketName).build()
);

4. Upload Object

PutObjectRequest request = PutObjectRequest.builder()
    .bucket(bucketName)
    .key(key)
    .contentType("application/pdf")
    .serverSideEncryption(ServerSideEncryption.AES256)
    .storageClass(StorageClass.STANDARD_IA)
    .build();

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

// Validate upload completion
HeadObjectResponse headResp = s3Client.headObject(HeadObjectRequest.builder()
    .bucket(bucketName)
    .key(key)
    .build());

5. Download Object

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

s3Client.getObject(request, Paths.get(destPath));

6. Generate Presigned URL

try (S3Presigner presigner = S3Presigner.create()) {
    GetObjectRequest getRequest = GetObjectRequest.builder()
        .bucket(bucketName)
        .key(key)
        .build();

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

    String url = presigner.presignGetObject(presignRequest).url().toString();
}

7. Use Transfer Manager (Large Files)

try (S3TransferManager tm = S3TransferManager.create()) {
    UploadFileRequest request = UploadFileRequest.builder()
        .putObjectRequest(req -> req.bucket(bucketName).key(key))
        .source(Paths.get(filePath))
        .build();

    FileUpload upload = tm.uploadFile(request);
    CompletedFileUpload result = upload.completionFuture().join();
}

Best Practices

Performance

  • Use S3 Transfer Manager: Automatic multipart uploads for files >100MB
  • Reuse S3 Client: Clients are thread-safe; reuse throughout application
  • Enable async operations: Use S3AsyncClient for I/O-bound operations
  • Configure timeouts: Set appropriate timeouts for large file operations

Security

  • Use temporary credentials: IAM roles or AWS STS for short-lived tokens
  • Enable encryption: Use AES-256 or AWS KMS for sensitive data
  • Use presigned URLs: Avoid exposing credentials with temporary access
  • Validate metadata: Sanitize user-provided metadata

Error Handling

  • Implement retry logic: Exponential backoff for network operations
  • Handle throttling: Proper handling of 429 responses
  • Clean up failures: Abort failed multipart uploads

Cost Optimization

  • Use appropriate storage classes: STANDARD, STANDARD_IA, INTELLIGENT_TIERING
  • Implement lifecycle policies: Automatic transition/expiration
  • Minimize API calls: Use batch operations when possible

Constraints and Warnings

  • Object Size: Single PUT limited to 5GB; use multipart 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
  • Presigned URLs: Maximum expiration time is 7 days
  • Multipart Uploads: Parts must be at least 5MB except last part

Examples

Complete Upload Workflow with Validation

// 1. Upload with validation
PutObjectRequest putRequest = PutObjectRequest.builder()
    .bucket(bucketName)
    .key(key)
    .contentType(contentType)
    .build();

s3Client.putObject(putRequest, RequestBody.fromFile(Paths.get(filePath)));

// 2. Validate with headObject
HeadObjectResponse headResp = s3Client.headObject(HeadObjectRequest.builder()
    .bucket(bucketName)
    .key(key)
    .build());

// 3. Verify metadata
long fileSize = Files.size(Paths.get(filePath));
if (headResp.contentLength() != fileSize) {
    throw new IllegalStateException("Upload size mismatch");
}

Multipart Upload with Abort-on-Failure

// 1. Initiate multipart upload
CreateMultipartUploadRequest createRequest = CreateMultipartUploadRequest.builder()
    .bucket(bucketName)
    .key(key)
    .build();

CreateMultipartUploadResponse multipartUpload = s3Client.createMultipartUpload(createRequest);
String uploadId = multipartUpload.uploadId();

try {
    // 2. Upload parts
    List<CompletedPart> parts = new ArrayList<>();
    int partNumber = 1;
    byte[] fileBytes = Files.readAllBytes(Paths.get(filePath));
    int chunkSize = 5 * 1024 * 1024; // 5MB minimum

    for (int offset = 0; offset < fileBytes.length; offset += chunkSize) {
        int length = Math.min(chunkSize, fileBytes.length - offset);
        UploadPartRequest uploadPartRequest = UploadPartRequest.builder()
            .bucket(bucketName)
            .key(key)
            .uploadId(uploadId)
            .partNumber(partNumber)
            .build();

        UploadPartResponse partResponse = s3Client.uploadPart(uploadPartRequest,
            RequestBody.fromBytes(Arrays.copyOfRange(fileBytes, offset, offset + length)));

        parts.add(CompletedPart.builder()
            .partNumber(partNumber)
            .eTag(partResponse.eTag())
            .build());
        partNumber++;
    }

    // 3. Complete multipart upload
    CompleteMultipartUploadRequest completeRequest = CompleteMultipartUploadRequest.builder()
        .bucket(bucketName)
        .key(key)
        .uploadId(uploadId)
        .multipartUpload(CompletedMultipartUpload.builder().parts(parts).build())
        .build();
    s3Client.completeMultipartUpload(completeRequest);

} catch (Exception e) {
    // 4. Abort on failure
    AbortMultipartUploadRequest abortRequest = AbortMultipartUploadRequest.builder()
        .bucket(bucketName)
        .key(key)
        .uploadId(uploadId)
        .build();
    s3Client.abortMultipartUpload(abortRequest);
    throw new RuntimeException("Upload failed, cleanup performed", e);
}

References

  • references/s3-client-setup.md — Client configuration and basic operations
  • references/s3-object-operations.md — Advanced object operations
  • references/s3-transfer-patterns.md — Transfer Manager and multipart uploads
  • references/s3-spring-boot-integration.md — Spring Boot integration patterns
  • 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

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