Stringify JSON object for SQL query in AWS AppSync

Question

Question: How can I stringify JSON object for SQL statement in my Appsync velocity template?

Explanation: I have an Aurora RDS table tha

Answer 1

You can build a JSON variable like this:

#set($json = $util.toJson({
  "connectionType": "$ctx.args.input.serviceConfig.connectionType",
  "capacity": $ctx.args.input.serviceConfig.capacity
  }))

And insert in your query:

{
    "version": "2018-05-29",
    "statements": [
        "INSERT INTO b2b_service_catalog(service_name, service_config) VALUES ('$ctx.args.input.serviceName', '$util.escapeJavaScript($json)' RETURNING service_id AS \"serviceId\", service_name AS \"serviceName\", service_config AS \"serviceConfig\"",
    ]
}

The above is a bit challenging because of all the quotes and escaping but I think the use of escapeJavaScript will do the trick.

Or directly:

{
    "version": "2018-05-29",
    "statements": [
        "INSERT INTO b2b_service_catalog(service_name, service_config) VALUES ('$ctx.args.input.serviceName', '{\"connectionType\":\"$ctx.args.input.serviceConfig.connectionType\",\"capacity\": $ctx.args.input.serviceConfig.capacity}') RETURNING service_id AS \"serviceId\", service_name AS \"serviceName\", service_config AS \"serviceConfig\"",
    ]
}

Answer 2

Solution 1:

Thanks to @cyberwombat I was able to fix this issue. I am posting this as a reference if someone needs it.

My serviceConfig object is not fixed and may change with time so I modified my resolver to make it more generic and it looks something like this:

#set($serviceConfigMap = {})

#foreach($key in $ctx.args.input.serviceConfig.keySet())
    $util.qr($serviceConfigMap.put("$key", $ctx.args.input.serviceConfig.get($key)))
#end

#set($serviceConfigMap = $util.toJson($serviceConfigMap))

{
    "version": "2018-05-29",
    "statements": [
        "INSERT INTO b2b_service_catalog(service_name, service_config) VALUES ('$ctx.args.input.serviceName', '$util.escapeJavaScript($serviceConfigMap)') RETURNING service_id AS \"serviceId\", service_name AS \"serviceName\", service_config AS \"serviceConfig\"",
    ]
}

Old Solution:

Here's how I solved this previously.

I converted my resolver to Pipeline and created a simple Lambda function in NodeJS to stringify the JSON object. This is how my lambda function looks like:

exports.handler = (event, context, callback) => {

    const response = {
        statusCode: 200,
        body: JSON.stringify(event.input.serviceConfig).replace(/\"/g, '\\\"'),
    };
    callback(null, response)
};

This is how serviceConfig looks like now and exactly how I wanted:

{\"connectionType\":\"ftth\",\"maxUploadCapacity\":1}"

I can now easily use it in my SQL statement within my resolver.