LambdaContainerHandler - Error while mapping object to RequestType class

*To help us debug your issue fill in the basic information below using the options provided*

*Serverless Java Container version*: `1.9`

*Implementations:* `Spring Boot 2`

*Framework version:* `SpringBoot 2.7.6.RELEASE`

*Frontend service:* `REST API`

*Deployment method:* `Console`

## Scenario
*Describe what you are trying to accomplish*
I have created an AP Gateway REST API which proxies to a Springboot Java application exposing differnet endpoints, mostly returning Monos and Fluxes. Payload inputted is below.
`{
"resource": "/{proxy+}",
"path": "/capitals",
"httpMethod": "GET",
"headers": {
"Accept": "application/json",
"Accept-Encoding": "gzip, deflate",
"Cache-Control": "no-cache",
"Content-Type": "application/json",
"Host": "xxxxxxx.execute-api.eu-north-1.amazonaws.com",
"Postman-Token": "zzzzzzz-4c21-4a6b-a71a-b5d39ce42332",
"User-Agent": "PostmanRuntime/7.28.4",
"X-Amzn-Trace-Id": "Root=1-638f4d15-626c445233b14ceb2f567363",
"X-BlueCoat-Via": "0drrr83fc54be448",
"X-Forwarded-For": "1.2.3.4",
"X-Forwarded-Port": "443",
"X-Forwarded-Proto": "https"
},
"multiValueHeaders": {
"Accept": [
"application/json"
],
"Accept-Encoding": [
"gzip, deflate"
],
"Cache-Control": [
"no-cache"
],
"Content-Type": [
"application/json"
],
"Host": [
"ay9vitrep4.execute-api.eu-north-1.amazonaws.com"
],
"Postman-Token": [
"zzzzzzz-4c21-4a6b-a71a-b5d39ce42332"
],
"User-Agent": [
"PostmanRuntime/7.28.4"
],
"X-Amzn-Trace-Id": [
"Root=1-638f4d15-626c445233b14ceb2f567363"
],
"X-BlueCoat-Via": [
"ggg3fc54be448"
],
"X-Forwarded-For": [
"1.2.3.4"
],
"X-Forwarded-Port": [
"443"
],
"X-Forwarded-Proto": [
"https"
]
},
"queryStringParameters": null,
"multiValueQueryStringParameters": null,
"pathParameters": {
"proxy": "capitals"
},
"stageVariables": null,
"requestContext": {
"resourceId": "sm5w9j",
"resourcePath": "/{proxy+}",
"httpMethod": "GET",
"extendedRequestId": "cuj7cEsTgi0FkCA=",
"requestTime": "06/Dec/2022:14:09:25 +0000",
"path": "/dev/capitals",
"accountId": "123456789",
"protocol": "HTTP/1.1",
"stage": "dev",
"domainPrefix": "ay9vitrep4",
"requestTimeEpoch": 1670335765833,
"requestId": "50facc59-b889-44a0-8a58-f86431bf0897",
"identity": {
"cognitoIdentityPoolId": null,
"accountId": null,
"cognitoIdentityId": null,
"caller": null,
"sourceIp": "1.2.3.4",
"principalOrgId": null,
"accessKey": null,
"cognitoAuthenticationType": null,
"cognitoAuthenticationProvider": null,
"userArn": null,
"userAgent": "PostmanRuntime/7.28.4",
"user": null
},
"domainName": "xxxxxxxxx.execute-api.eu-north-1.amazonaws.com",
"apiId": "xxxxxxxx"
},
"body": null,
"isBase64Encoded": false
}`

Nevertheless, when executing the endpoint, the call fails as seems that above payload cannot be mapped into a RequestType class (which is an AWSProxyRequest)

[main] ERROR com.amazonaws.serverless.proxy.internal.LambdaContainerHandler - Error while mapping object to RequestType class
  | 2022-12-06T15:38:16.811+01:00 | com.fasterxml.jackson.databind.exc.MismatchedInputException: No content to map due to end-of-input

## Expected behavior
*Describe how you would expect the application to behave*
Json Payload should be returned with 200 response

## Actual behavior
*Describe what you are seeing instead*
Response returns 502 with this error inCloudwatch:

` [main] ERROR com.amazonaws.serverless.proxy.internal.LambdaContainerHandler - Error while mapping object to RequestType class
  | 2022-12-06T15:38:16.811+01:00 | com.fasterxml.jackson.databind.exc.MismatchedInputException: No content to map due to end-of-input`

## Steps to reproduce
*Provide code samples we can use to reproduce the issue as part of our integration tests. If there is a public repository for the misbehaving application link to it here*
1) Added aws-serverless-java-container springboot2 library in pom, version 1.9
2)Added LambdaHandler as below
```
public class StreamLambdaHandler implements RequestStreamHandler {
private static SpringBootLambdaContainerHandler handler;
static {
try {
handler = SpringBootLambdaContainerHandler.getAwsProxyHandler(Application.class);
// If you are using HTTP APIs with the version 2.0 of the proxy model, use the getHttpApiV2ProxyHandler
// method: handler = SpringBootLambdaContainerHandler.getHttpApiV2ProxyHandler(Application.class);
} catch (ContainerInitializationException e) {
// if we fail here. We re-throw the exception to force another cold start
e.printStackTrace();
throw new RuntimeException("Could not initialize Spring Boot application", e);
}
}

@Override
public void handleRequest(InputStream inputStream, OutputStream outputStream, Context context)
throws IOException {
handler.proxyStream(inputStream, outputStream, context);
}
}
```
3)Add typical Application (annotated with @SpringBootpplication) + a RestController with this class:
```
@RestController
public class Resource {

private AService service;

public Resource1(AService service) {
this.service = service;
}

@GetMapping("/capitals")
public Mono getMono() {
return service.serve()
.collectList()
.map(Capitals::new);
}

@Data
private class Capitals {
final List values;
}
}
```
Service class:

````
@Service
public class AService {

public static final List capitals = Arrays.asList("Copenhagen", "Rome", "Berlin", "Reykjavik");

public Flux serve() {
return Flux.fromIterable(capitals);
}
}
```

## Full log output
*Paste the full log output from the Lambda function's CloudWatch logs*

```

2022-12-06T15:38:16.811+01:00 | 14:38:16.811 [main] ERROR com.amazonaws.serverless.proxy.internal.LambdaContainerHandler - Error while mapping object to RequestType class
-- | --
  | 2022-12-06T15:38:16.811+01:00 | com.fasterxml.jackson.databind.exc.MismatchedInputException: No content to map due to end-of-input
  | 2022-12-06T15:38:16.811+01:00 | at [Source: (ByteArrayInputStream); line: 1, column: 0]
  | 2022-12-06T15:38:16.811+01:00 | at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:59)
  | 2022-12-06T15:38:16.811+01:00 | at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1741)
  | 2022-12-06T15:38:16.811+01:00 | at com.fasterxml.jackson.databind.ObjectReader._initForReading(ObjectReader.java:359)
  | 2022-12-06T15:38:16.811+01:00 | at com.fasterxml.jackson.databind.ObjectReader._bindAndClose(ObjectReader.java:2041)
  | 2022-12-06T15:38:16.811+01:00 | at com.fasterxml.jackson.databind.ObjectReader.readValue(ObjectReader.java:1427)
  | 2022-12-06T15:38:16.811+01:00 | at com.amazonaws.serverless.proxy.internal.LambdaContainerHandler.proxyStream(LambdaContainerHandler.java:256)
  | 2022-12-06T15:38:16.811+01:00 | at com.nordea.ndf.lambda.StreamLambdaHandler.handleRequest(StreamLambdaHandler.java:42)
  | 2022-12-06T15:38:16.811+01:00 | at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  | 2022-12-06T15:38:16.811+01:00 | at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
  | 2022-12-06T15:38:16.811+01:00 | at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
  | 2022-12-06T15:38:16.811+01:00 | at java.base/java.lang.reflect.Method.invoke(Unknown Source)
  | 2022-12-06T15:38:16.811+01:00 | at lambdainternal.EventHandlerLoader$StreamMethodRequestHandler.handleRequest(EventHandlerLoader.java:375)
  | 2022-12-06T15:38:16.811+01:00 | at lambdainternal.EventHandlerLoader$2.call(EventHandlerLoader.java:899)
  | 2022-12-06T15:38:16.811+01:00 | at lambdainternal.AWSLambda.startRuntime(AWSLambda.java:268)
  | 2022-12-06T15:38:16.811+01:00 | at lambdainternal.AWSLambda.startRuntime(AWSLambda.java:206)
  | 2022-12-06T15:38:16.811+01:00 | at lambdainternal.AWSLambda.main(AWSLambda.java:200)
  | 2022-12-06T15:38:16.811+01:00 | 14:38:16.811 [main] ERROR com.amazonaws.serverless.proxy.AwsProxyExceptionHandler - Called exception handler for:
  | 2022-12-06T15:38:16.811+01:00 | com.fasterxml.jackson.databind.exc.MismatchedInputException: No content to map due to end-of-input
  | 2022-12-06T15:38:16.811+01:00 | at [Source: (ByteArrayInputStream); line: 1, column: 0]
  | 2022-12-06T15:38:16.811+01:00 | at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:59)
  | 2022-12-06T15:38:16.811+01:00 | at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1741)
  | 2022-12-06T15:38:16.811+01:00 | at com.fasterxml.jackson.databind.ObjectReader._initForReading(ObjectReader.java:359)
  | 2022-12-06T15:38:16.811+01:00 | at com.fasterxml.jackson.databind.ObjectReader._bindAndClose(ObjectReader.java:2041)
  | 2022-12-06T15:38:16.811+01:00 | at com.fasterxml.jackson.databind.ObjectReader.readValue(ObjectReader.java:1427)
  | 2022-12-06T15:38:16.811+01:00 | at com.amazonaws.serverless.proxy.internal.LambdaContainerHandler.proxyStream(LambdaContainerHandler.java:256)
  | 2022-12-06T15:38:16.811+01:00 | at com.nordea.ndf.lambda.StreamLambdaHandler.handleRequest(StreamLambdaHandler.java:42)
  | 2022-12-06T15:38:16.811+01:00 | at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  | 2022-12-06T15:38:16.811+01:00 | at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
  | 2022-12-06T15:38:16.811+01:00 | at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
  | 2022-12-06T15:38:16.811+01:00 | at java.base/java.lang.reflect.Method.invoke(Unknown Source)
  | 2022-12-06T15:38:16.811+01:00 | at lambdainternal.EventHandlerLoader$StreamMethodRequestHandler.handleRequest(EventHandlerLoader.java:375)
  | 2022-12-06T15:38:16.811+01:00 | at lambdainternal.EventHandlerLoader$2.call(EventHandlerLoader.java:899)
  | 2022-12-06T15:38:16.811+01:00 | at lambdainternal.AWSLambda.startRuntime(AWSLambda.java:268)
  | 2022-12-06T15:38:16.811+01:00 | at lambdainternal.AWSLambda.startRuntime(AWSLambda.java:206)
  | 2022-12-06T15:38:16.811+01:00 | at lambdainternal.AWSLambda.main(AWSLambda.java:200)
  | 2022-12-06T15:38:16.812+01:00 | com.fasterxml.jackson.databind.exc.MismatchedInputException: No content to map due to end-of-input
  | 2022-12-06T15:38:16.812+01:00 | at [Source: (ByteArrayInputStream); line: 1, column: 0]
  | 2022-12-06T15:38:16.812+01:00 | at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:59)
  | 2022-12-06T15:38:16.812+01:00 | at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1741)
  | 2022-12-06T15:38:16.812+01:00 | at com.fasterxml.jackson.databind.ObjectReader._initForReading(ObjectReader.java:359)
  | 2022-12-06T15:38:16.812+01:00 | at com.fasterxml.jackson.databind.ObjectReader._bindAndClose(ObjectReader.java:2041)
  | 2022-12-06T15:38:16.812+01:00 | at com.fasterxml.jackson.databind.ObjectReader.readValue(ObjectReader.java:1427)
  | 2022-12-06T15:38:16.812+01:00 | at com.amazonaws.serverless.proxy.internal.LambdaContainerHandler.proxyStream(LambdaContainerHandler.java:256)
  | 2022-12-06T15:38:16.812+01:00 | at com.nordea.ndf.lambda.StreamLambdaHandler.handleRequest(StreamLambdaHandler.java:42)
  | 2022-12-06T15:38:16.812+01:00 | at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
  | 2022-12-06T15:38:16.812+01:00 | at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
  | 2022-12-06T15:38:16.828+01:00 | at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
  | 2022-12-06T15:38:16.848+01:00 | at java.base/java.lang.reflect.Method.invoke(Unknown Source)
  | 2022-12-06T15:38:16.848+01:00 | at lambdainternal.EventHandlerLoader$StreamMethodRequestHandler.handleRequest(EventHandlerLoader.java:375)
  | 2022-12-06T15:38:16.848+01:00 | at lambdainternal.EventHandlerLoader$2.call(EventHandlerLoader.java:899)
  | 2022-12-06T15:38:16.848+01:00 | at lambdainternal.AWSLambda.startRuntime(AWSLambda.java:268)
  | 2022-12-06T15:38:16.848+01:00 | at lambdainternal.AWSLambda.startRuntime(AWSLambda.java:206)

```