I want to have one lambda function tat can be triggered by multiple sources

1. When I upload an xml document in S3 bucket
2. Via APIGateway request

I tried the following

public class MultiTriggerLambda implements RequestHandler<Object, Object> {

private final AmazonS3 s3Client = AmazonS3ClientBuilder.defaultClient();

@Override
public Object handleRequest(Object event, Context context) {
    if (event instanceof S3Event) {
        // S3 Trigger
        return handleS3Event((S3Event) event, context);
    } else if (event instanceof APIGatewayProxyRequestEvent) {
        // API Gateway Trigger
        return handleApiGatewayRequest((APIGatewayProxyRequestEvent) event, context);
    } else {
        // Unknown Event
        return "Unknown event source";
    }
}

The issue is the event coming from S3 is not an instance of S3Event but its a map.

Can I somehow configure my lambda or S3 event so that I get the event as of type S3Event and APIGatewayProxyRequestEvent and not Map?

Thanks