REST XML

aws.protocols#restXml is the XML-over-HTTP protocol used by AWS services such as S3 and Route 53. NSmithy generates a typed client that encodes request bodies as XML and decodes XML responses. Status: Early preview, client-only.

Maven Dependency

"software.amazon.smithy:smithy-aws-traits:1.56.0"

NuGet Package

<PackageReference Include="NSmithy.Codecs.Xml" Version="0.1.0-preview.15" />

Modeling

Apply @restXml to the service and @http to each operation, the same as simpleRestJson. Use @xmlName to override the XML element name for a member:

$version: "2"

namespace example.hello

use aws.protocols#restXml

@restXml
service HelloService {
    version: "2026-01-01"
    operations: [SayHello]
}

@http(method: "POST", uri: "/hello")
operation SayHello {
    input := {
        @required
        name: String
    }
    output := {
        @required
        @xmlName("Message")
        message: String
    }
}

@xmlName overrides the element name in the serialized XML. Without it the member name is used as-is.

HTTP binding traits (@httpLabel, @httpQuery, @httpHeader, @httpPayload) work the same way as in simpleRestJson — members without an explicit binding go into the XML body.

Client

The XML codec is wired up automatically by the generated client:

using Example.Hello;
using NSmithy.Client;

var client = new HelloServiceClient(
    new HttpClient(),
    new SmithyClientOptions { Endpoint = new Uri("https://api.example.com") }
);

var response = await client.SayHelloAsync(new SayHelloInput("world"));
Console.WriteLine(response.Message);