"Error deserializing the input JSON" on completely stock empty function template

[nholms]

Created an "Empty Function" new solution with VS2017 using AWS Toolkit templates. Making no changes to the generated solution I run the "Mock Lambda Test Tool" launch profile and select the "Hello World" example request.

{
  "key1": "value1",
  "key2": "value2",
  "key3": "value3"
}

The resulting error is below... I'm having trouble trying to identify the root cause and solution.

System.Exception: Error deserializing the input JSON to type String
   at Amazon.Lambda.TestTool.Runtime.LambdaExecutor.BuildParameters(ExecutionRequest request, ILambdaContext context) in E:\JenkinsWorkspaces\Lam\LambdaSandboxCoreCLRApi\Tools\LambdaTestTool\Amazon.Lambda.TestTool\Runtime\LambdaExecutor.cs:line 201
   at Amazon.Lambda.TestTool.Runtime.LambdaExecutor.Execute(ExecutionRequest request) in E:\JenkinsWorkspaces\Lam\LambdaSandboxCoreCLRApi\Tools\LambdaTestTool\Amazon.Lambda.TestTool\Runtime\LambdaExecutor.cs:line 44
---------------- Inner 1 Exception ------------
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at Amazon.Lambda.TestTool.Runtime.LambdaExecutor.BuildParameters(ExecutionRequest request, ILambdaContext context) in E:\JenkinsWorkspaces\Lam\LambdaSandboxCoreCLRApi\Tools\LambdaTestTool\Amazon.Lambda.TestTool\Runtime\LambdaExecutor.cs:line 193
---------------- Inner 2 Exception ------------
Amazon.Lambda.Serialization.Json.JsonSerializerException: Error converting the Lambda event JSON payload to a string. JSON strings must be quoted, for example "Hello World" in order to be converted to a string: Unexpected character encountered while parsing value: {. Path '', line 1, position 1.
   at Amazon.Lambda.Serialization.Json.JsonSerializer.Deserialize[T](Stream requestStream)
---------------- Inner 3 Exception ------------
Newtonsoft.Json.JsonReaderException: Unexpected character encountered while parsing value: {. Path '', line 1, position 1.
   at Newtonsoft.Json.JsonTextReader.ReadStringValue(ReadType readType)
   at Newtonsoft.Json.JsonTextReader.ReadAsString()
   at Newtonsoft.Json.JsonReader.ReadForType(JsonContract contract, Boolean hasConverter)
   at Newtonsoft.Json.Serialization.JsonSerializerInternalReader.Deserialize(JsonReader reader, Type objectType, Boolean checkAdditionalContent)
   at Newtonsoft.Json.JsonSerializer.DeserializeInternal(JsonReader reader, Type objectType)
   at Newtonsoft.Json.JsonSerializer.Deserialize[T](JsonReader reader)
   at Amazon.Lambda.Serialization.Json.JsonSerializer.Deserialize[T](Stream requestStream)

[vellozzi]

I'm guessing the first parameter of your function handler is a string
Lambda is looking for is a JSON string "string including quotes" not a JSON object {"prop":"value"}

You should change the input for your test to be a JSON string or change the function to take an object. The object option is a little more involved. You need to add a NuGet reference to

Amazon.Lambda.Serialization.Json

and add

[assembly: Amazon.Lambda.Core.LambdaSerializer(typeof(Amazon.Lambda.Serialization.Json.JsonSerializer))]

to your function's assembly.

[nholms]

The test works quite well with either a string or a null input but that's not the problem here. The template as listed includes the elements that you're suggesting. It seems that even with the LambdaSerializer specified there is still an issue.

https://github.com/aws/aws-lambda-dotnet/blob/master/Blueprints/BlueprintDefinitions/Msbuild-NETCore_2_1/EmptyFunction/template/src/BlueprintBaseName.1/Function.cs

[vellozzi]

If your code looks just like https://github.com/aws/aws-lambda-dotnet/blob/master/Blueprints/BlueprintDefinitions/Msbuild-NETCore_2_1/EmptyFunction/template/src/BlueprintBaseName.1/Function.cs then I think my advice still applies.

If that's the case your function won't accept {"Prop":"Value"} as input.
If you want to send {"Prop":"value"} you have to define a class like:

class FunctionInput
{
    public string Prop { get; set; }
}

and your function signature should look like

public string FunctionHandler(FunctionInput input, ILambdaContext context)

Does that help, or is there something I'm still not seeing?

[nholms]

Ok thanks, I think I see what you're getting at. I was expecting a raw string. Specifying an object like the below allows the "Hello World" test from the mock test tool to work properly...

public class InputTest
{
    public string Key1;
    public string Key2;
    public string Key3;
}

[vellozzi]

OK. I'm glad that helped.

[Wizard2436829]

Hi Guys,

I am actually trying to use AWS connect with AWS Lambda and according to the official documentation: https://docs.aws.amazon.com/connect/latest/adminguide/connect-lambda-functions.html

There is a specific JSON format in which connect makes a request to the lambda function.

I have already tried the C# object approach to bind the connect request with the lambda function.

My problem is that even after the request is generated by connect , it needs slight modification(Manually) and then when i test it with lambda its works fine.

I Actually need to feed that RAW JSON to the method and then deserialize it in my method and attach it with the object.

Does anyone have a clue how to go forward with the RAW JSON input to method parameter.

[klaytaybai]

@Wizard2436829, I think you should create a separate issue.

[RobKraft]

The AWS-SDK for Visual Studio 2019 creates the stub of FunctionHandler for you. Unfortunately it is created incorrectly like this:
public string FunctionHandler(string input, ILambdaContext context)
change that to something like:
public object FunctionHandler(Stream input, ILambdaContext context)
and you should be able to get going.

[richardkeller411]

The Message Body has to be a string. Just Stringy the Json.

https://onlinetexttools.com/json-stringify-text