JSON to String API GATEWAY ( AWS )

Question

I need to receive a JSON in my API GATEWAY and pass to my LAMBDA ( GOLANG ) a STRING, The Structure Apigatewayproxyrequest the body is String type, when I try to call the lambda passing the json the same break, i need to create a model that converts the received JSON into the STRING gateway before going pro lambda.

Example of how it is today :

##set($allParams = $input.params())
{
## Repassando o json para o lambda
"body":"$util.escapeJavaScript($input.body)",
##"body":"$util.escapeJavaScript($input.body).replaceAll('\"','\\\"')",
## Populando o Headers
"headers": {
    ## Pegando todos os parametros do header e setando
    #foreach($param in $input.params().header.keySet())
    "$param": "$util.escapeJavaScript($input.params().header.get($param))"
    #if($foreach.hasNext),#end
    #end
}
}

Where BODY is of type STRING. When I pass something like :

"body":{"email":"[email protected]","senha":"1234"}

I get error , but if I pass :

"body":"{\"email\":\"[email protected]\",\"senha\":\"1234\"}"

Works normally, already removed the util.escape and nothing I need a model to solve this, taking the JSON and converting to the string type that works , so when I get to the lambda I parse.

Struct lambda

type APIGatewayProxyRequest struct {
Resource                        string                        `json:"resource"` // The resource path defined in API Gateway
Path                            string                        `json:"path"`     // The url path for the caller
HTTPMethod                      string                        `json:"httpMethod"`
Headers                         map[string]string             `json:"headers"`
MultiValueHeaders               map[string][]string           `json:"multiValueHeaders"`
QueryStringParameters           map[string]string             `json:"queryStringParameters"`
MultiValueQueryStringParameters map[string][]string           `json:"multiValueQueryStringParameters"`
PathParameters                  map[string]string             `json:"pathParameters"`
StageVariables                  map[string]string             `json:"stageVariables"`
RequestContext                  APIGatewayProxyRequestContext `json:"requestContext"`
Body                            string                        `json:"body"`
IsBase64Encoded                 bool                          `json:"isBase64Encoded,omitempty"`
}

Answer 1

The Amazon Gateway API only receives if it is a string, if you pass any other type of data parse error happens, and also Response has a defined structure. In case you can transform your struct into []byte and then pass as string, example as I do:

func buildBody(statusCode int, body []byte) events.APIGatewayProxyResponse {
    return events.APIGatewayProxyResponse{
        StatusCode: statusCode,
        Headers: map[string]string{
            "Content-Type":                 "application/json; charset=utf-8",
            "Access-Control-Allow-Origin":  "*",
            "Access-Control-Allow-Methods": "OPTIONS, HEAD, GET, POST, PUT, DELETE",
            "Access-Control-Allow-Headers": "Content-Type,X-Amz-Date,Authorization,X-Api-Key,x-requested-with",
            "X-Requested-With":             "*",
        },
        MultiValueHeaders: nil,
        Body:              string(body),
        IsBase64Encoded:   false,
    }
}

Documentation about what I’m talking about: https://aws.amazon.com/pt/premiumsupport/knowledge-center/malformed-502-api-gateway/

The body field, if you’re returning JSON, must be converted to a string to Prevent further problems with the Response. You can use JSON.stringify to Handle this in Node.js functions. Other runtimes require Different Solutions, but the Concept is the same.