AwsLambda.Host.Envelopes.Sns 1.3.1

AwsLambda.Host.Envelopes.Sns

Strongly-typed SNS event handling for the AwsLambda.Host framework.

Overview

This package provides SnsEnvelope<T>, which extends the base SNSEvent class with strongly-typed Records collection that deserializes message bodies into strongly-typed objects. Instead of manually parsing JSON from record.Sns.Message, you access deserialized payloads directly via record.Sns.MessageContent.

Quick Start

Define your message type and handler:

using Amazon.Lambda.SNSEvents;
using AwsLambda.Host.Builder;
using AwsLambda.Host.Envelopes.Sns;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;

var builder = LambdaApplication.CreateBuilder();
var lambda = builder.Build();

// SnsEnvelope<Message> provides access to the SNS event and deserialized Message payloads
lambda.MapHandler(
 ([Event] SnsEnvelope<Message> envelope, ILogger<Program> logger) =>
 {
 foreach (var record in envelope.Records)
 {
 logger.LogInformation("Message: {Content}", record.Sns.MessageContent?.Content);
 }
 }
);

await lambda.RunAsync();

// Your message payload - will be deserialized from SNS message body
internal record Message(string Content);

Custom Envelopes

To implement custom deserialization logic, extend SnsEnvelopeBase<T> and override the ExtractPayload method:

// Example: Custom XML deserialization
public sealed class SnsXmlEnvelope<T> : SnsEnvelopeBase<T>
{
 private static readonly XmlSerializer Serializer = new(typeof(T));

 public override void ExtractPayload(EnvelopeOptions options)
 {
 foreach (var record in Records)
 {
 using var stringReader = new StringReader(record.Sns.Message);
 using var xmlReader = XmlReader.Create(stringReader, options.XmlReaderSettings);
 record.Sns.MessageContent = (T)Serializer.Deserialize(xmlReader)!;
 }
 }
}

This pattern allows you to support multiple serialization formats while maintaining the same envelope interface.

AOT Support

When using .NET Native AOT, register both the envelope and payload types in your JsonSerializerContext:

[JsonSerializable(typeof(SnsEnvelope<Message>))]
[JsonSerializable(typeof(Message))]
internal partial class SerializerContext : JsonSerializerContext;

Register the serializer and configure envelope options to use the context:

builder.Services.AddLambdaSerializerWithContext<SerializerContext>();

builder.Services.ConfigureEnvelopeOptions(options =>
{
 options.JsonOptions.TypeInfoResolver = SerializerContext.Default;
});

Other Packages

Additional packages in the aws-lambda-host framework for abstractions, observability, and event source handling.

License

This project is licensed under the MIT License. See for details.