AWS S3

Description

AWS S3 can be used as the backing implementation for Flex file operations. Your application code should depend on IFlexFileStore, while Flex provides the provider bridge and wiring.

Important concepts

• IFlexFileStore is the contract: app code uploads/downloads using the shared interface rather than AWS SDK types.

• Files are streamed: uploads use a Stream; downloads return a Stream? (when a file doesn’t exist, you should handle null).

• Provider bridge: the AWS implementation is exposed via an IFlexFileStoreBridge internally, but most consumers only need IFlexFileStore.

Configuration in DI

Add the provider in your DI composition root (commonly in EndPoints/...CommonConfigs/OtherApplicationServicesConfig.cs or wherever you centralize registrations).

// using Sumeru.Flex; // IFlexFileStore

public static class OtherApplicationServicesConfig
{
	public static IServiceCollection AddOtherApplicationServices(
		this IServiceCollection services,
		IConfiguration configuration)
	{
		// Registers AWS S3 as the IFlexFileStore bridge.
		// Flex auto-wires generated Queries/Handlers that *use* IFlexFileStore.
		services.AddFlexAwsS3FileStore(configuration);

		return services;
	}
}

appsettings.json

Configuration is read from FlexBase:DataStores:File:AwsS3.

{
  "FlexBase": {
	"DataStores": {
	  "File": {
		"AwsS3": {
		  "AccessKeyId": "...",
		  "SecretAccessKey": "...",
		  "Region": "us-east-1",
		  "BucketName": "your-bucket-name",
		  "ServiceUrl": null
		}
	  }
	}
  }
}

Examples (template-based)

These examples mirror the generated Query and PostBusHandler templates. You do not register these types manually—Flex discovers and wires generated Queries/Handlers automatically.

Upload file (PostBusHandler)

using Microsoft.Extensions.Logging;
using Sumeru.Flex;
using System.IO;
using System.Threading.Tasks;

namespace {YourApplication}.Handlers.Files;

public partial class UploadFileHandler : IAmFlexCommandHandler<UploadFileCommand>
{
	protected string EventCondition = "";

	protected readonly ILogger<UploadFileHandler> _logger;
	protected readonly IFlexHost _flexHost;
	protected readonly IFlexFileStore _fileStore;

	public UploadFileHandler(ILogger<UploadFileHandler> logger, IFlexHost flexHost, IFlexFileStore fileStore)
	{
		_logger = logger;
		_flexHost = flexHost;
		_fileStore = fileStore;
	}

	public virtual async Task Execute(UploadFileCommand cmd, IFlexServiceBusContext serviceBusContext)
	{
		_logger.LogDebug("Starting Upload for {EntityType}", nameof(FileModel));

		var appContext = cmd.Dto.GetAppContext(); // do not remove this line

		var model = _flexHost.GetDomainModel<FileModel>().Create(cmd);

		var fileId = await _fileStore.UploadAsync(
			cmd.Dto.Stream,
			cmd.Dto.FileName,
			cmd.Dto.ContentType,
			cmd.Dto.Metadata);

		// Example:
		// EventCondition = UploadFileEvents.CONDITION_ONSUCCESS;
		await this.Fire(EventCondition, serviceBusContext);

		_logger.LogDebug("Completed Upload for {EntityType} {FileId}, Event: {EventCondition}", nameof(FileModel), fileId, EventCondition);
	}
}

public class UploadFileCommand : FlexCommandBridge<UploadFileDto> { }

public class UploadFileDto : DtoBridge
{
	public Stream Stream { get; set; }
	public string FileName { get; set; }
	public string ContentType { get; set; }
	public IDictionary<string, string>? Metadata { get; set; }
}

public class FileModel : FlexDomainModelBridge { }

Download file (Query)

using Microsoft.Extensions.Logging;
using Sumeru.Flex;
using System.IO;
using System.Threading.Tasks;

namespace {YourApplication}.Queries.Files;

public class DownloadFileQuery : FlexiQueryBridgeAsync<FileDownloadOutput>
{
	protected readonly ILogger<DownloadFileQuery> _logger;
	protected readonly IFlexHost _flexHost;
	protected readonly IFlexFileStore _fileStore;
	protected DownloadFileParams _params;

	public DownloadFileQuery(ILogger<DownloadFileQuery> logger, IFlexHost flexHost, IFlexFileStore fileStore)
	{
		_logger = logger;
		_flexHost = flexHost;
		_fileStore = fileStore;
	}

	public virtual DownloadFileQuery AssignParameters(DownloadFileParams @params)
	{
		_params = @params;
		return this;
	}

	public virtual async Task<FileDownloadOutput?> Fetch()
	{
		var appContext = _params.GetAppContext();

		var stream = await _fileStore.DownloadAsync(_params.FileId);
		if (stream == null)
		{
			return default;
		}

		return new FileDownloadOutput
		{
			FileId = _params.FileId,
			Stream = stream
		};
	}
}

public class DownloadFileParams : DtoBridge
{
	public string FileId { get; set; }
}

public class FileDownloadOutput : DtoBridge
{
	public string FileId { get; set; }
	public Stream Stream { get; set; }
	public string? FileName { get; set; }
	public string? ContentType { get; set; }
}

Library-specific considerations

• Credentials: prefer environment/secret manager injection; avoid committing AccessKeyId / SecretAccessKey to source control.

• Bucket policy: the executing identity typically needs s3:GetObject, s3:PutObject, and s3:ListBucket.

• ServiceUrl: useful for S3-compatible endpoints (for example LocalStack or MinIO).