Introducing S3Link to DynamoDBContext

S3Link has been in the AWS SDK for Java for a while now, and we have decided to introduce it to the AWS SDK for .NET as well. This feature allows you to access your Amazon S3 resources easily through a link in your Amazon DynamoDB data. S3Link can be used with minimal configuration with the .NET DynamoDB Object Persistence Model. To use S3Link, simply add it as a field to your DynamoDB annotated class and create a bucket in S3. The following Book class has an S3Link property named CoverImage.

// Create a class for DynamoDBContext
[DynamoDBTable("Library")]
public class Book
{
	[DynamoDBHashKey]   
	public int Id { get; set; }

	public S3Link CoverImage { get; set; }

	public string Title { get; set; }
	public int ISBN { get; set; }

	[DynamoDBProperty("Authors")]    
	public List BookAuthors { get; set; }
}

Now that we have an S3Link in our annotated class, we are ready to manage an S3 object. The following code does four things:

1. Creates and saves a book to DynamoDB
2. Uploads the cover of the book to S3
3. Gets a pre-signed URL to the uploaded object
4. Loads the book back in using the Context object and downloads the cover of the book to a local file

// Create a DynamoDBContext
var context = new DynamoDBContext();

// Create a book with an S3Link
Book myBook = new Book
{
	Id = 501,
	CoverImage = S3Link.Create(context, "myBucketName", "covers/AWSSDK.jpg", Amazon.RegionEndpoint.USWest2),
	Title = "AWS SDK for .NET Object Persistence Model Handling Arbitrary Data",
	ISBN = 999,
	BookAuthors = new List { "Jim", "Steve", "Pavel", "Norm", "Milind" }
};

// Save book to DynamoDB
context.Save(myBook);

// Use S3Link to upload the content to S3
myBook.CoverImage.UploadFrom("path/to/covers/AWSSDK.jpg");

// Get a pre-signed URL for the image
string coverURL = myBook.CoverImage.GetPreSignedURL(DateTime.Now.AddHours(5));

// Load book from DynamoDB
myBook = context.Load(501);

// Download file linked from S3Link
myBook.CoverImage.DownloadTo("path/to/save/cover/otherbook.jpg");

And that’s the general use for S3Link. Simply provide it a bucket and a key, and then you can upload and download your data.