Amazon.Lambda.Serialization.SystemTextJson 2.4.1
Amazon.Lambda.Serialization.SystemTextJson
This package contains a custom Amazon.Lambda.Core.ILambdaSerializer
implementation which uses System.Text.Json to
serialize/deserialize .NET types in Lambda functions. This serializer targets .NET Core 3.1 so can not be used with
the .NET Core 2.1 Lambda runtime.
If targeting .NET Core 3.1 this serializer is highly recommend over Amazon.Lambda.Serialization.Json and can significantly reduce cold start performance in Lambda.
This serializer can be present on the assembly or on the handler method. If you specify both, the method attribute takes priority.
Here is an example of setting this attribute on the assembly.
[assembly: Amazon.Lambda.Core.LambdaSerializer(typeof(Amazon.Lambda.Serialization.SystemTextJson.DefaultLambdaJsonSerializer))]
And this is how the method can be applied to the handler method.
[Amazon.Lambda.Core.LambdaSerializer(typeof(Amazon.Lambda.Serialization.SystemTextJson.DefaultLambdaJsonSerializer))]
public Response CustomSerializerMethod(Request input)
{
...
}
Using C# source generator for serialization
C# 9 provides source generators, which allow code generation during compilation. This can reduce the use of reflection APIs and improve application startup time. .NET 6 updated the native JSON library System.Text.Json to use source generators, allowing JSON parsing without requiring reflection APIs.
To use the source generator for JSON serializing in Lambda, you must define a new empty class
in your project that derives from System.Text.Json.Serialization.JsonSerializerContext
. This
class must be a partial class because the source generator adds code to this class to handle
serialization. On the empty partial class, add the JsonSerializable
attribute for each .NET
type the source generator must generate the serialization code for.
Here is an example called HttpApiJsonSerializerContext that registers the Amazon API Gateway HTTP API event and response types to have the serialization code generated:
[JsonSerializable(typeof(APIGatewayHttpApiV2ProxyRequest))]
[JsonSerializable(typeof(APIGatewayHttpApiV2ProxyResponse))]
public partial class HttpApiJsonSerializerContext : JsonSerializerContext
{
}
To register the source generator for serialization use the LambdaSerializer
attribute
passing in the SourceGeneratorLambdaJsonSerializer
type along with the custom context
type (i.e. HttpApiJsonSerializerContext
) as the generic parameter.
[assembly: LambdaSerializer(
typeof(SourceGeneratorLambdaJsonSerializer
<APIGatewayExampleImage.HttpApiJsonSerializerContext>))]
Customizing serialization options
Both DefaultLambdaJsonSerializer
and SourceGeneratorLambdaJsonSerializer
construct an
instance of JsonSerializerOptions
that is used to customize the serialization and deserialization
of the Lambda JSON events. For example adding special converters and naming policies.
To further customize the JsonSerializerOptions
create a new type extending from extend
either DefaultLambdaJsonSerializer
or SourceGeneratorLambdaJsonSerializer
and pass
in an Action
customizer to the base constructor. Then register the new type as the
serializer using the LambdaSerializer
attribute. Below is an example of a custom serializer.
public class CustomLambdaSerializer : DefaultLambdaJsonSerializer
{
public CustomLambdaSerializer()
: base(CreateCustomizer())
{ }
private static Action<JsonSerializerOptions> CreateCustomizer()
{
return (JsonSerializerOptions options) =>
{
// Customize options
};
}
}
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.NET Core 3.1
- Amazon.Lambda.Core (>= 2.2.0)
.NET 6.0
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.NET 8.0
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