Pass URL path parameters from API Gateway to step function

Question

I have an API gateway route with a Step Function integration.

In this step function, I need the id given by the request.

With a lambda integration I understand how to do it, but in this case I do not find any ressource. Is it possible, and if yes, how ?

Answer 1

Adapt this VTL request mapping template^* to add the path parameters to the state machine input.

• Replace %STATEMACHINE% with your State Machine's ARN
• Optionally set $includeHeaders or $includeQueryString to false.
• Optionally set $requestContext to context key-value pairs. Use @@ instead of quotes, as in "{@@user@@:@@$context.identity.user@@}".

## Velocity Template used for API Gateway request mapping template
## "@@" is used here as a placeholder for '"' to avoid using escape characters.

#set($includeHeaders = true)
#set($includeQueryString = true)
#set($includePath = true)
#set($requestContext = '')

#set($inputString = '')
#set($allParams = $input.params())
{
    "stateMachineArn": "%STATEMACHINE%",

    #set($inputString = "$inputString,@@body@@: $input.body")

    #if ($includeHeaders)
        #set($inputString = "$inputString, @@header@@:{")
        #foreach($paramName in $allParams.header.keySet())
            #set($inputString = "$inputString @@$paramName@@: @@$util.escapeJavaScript($allParams.header.get($paramName))@@")
            #if($foreach.hasNext)
                #set($inputString = "$inputString,")
            #end
        #end
        #set($inputString = "$inputString }")
        
    #end

    #if ($includeQueryString)
        #set($inputString = "$inputString, @@querystring@@:{")
        #foreach($paramName in $allParams.querystring.keySet())
            #set($inputString = "$inputString @@$paramName@@: @@$util.escapeJavaScript($allParams.querystring.get($paramName))@@")
            #if($foreach.hasNext)
                #set($inputString = "$inputString,")
            #end
        #end
        #set($inputString = "$inputString }")
    #end

    #if ($includePath)
        #set($inputString = "$inputString, @@path@@:{")
        #foreach($paramName in $allParams.path.keySet())
            #set($inputString = "$inputString @@$paramName@@: @@$util.escapeJavaScript($allParams.path.get($paramName))@@")
            #if($foreach.hasNext)
                #set($inputString = "$inputString,")
            #end
        #end
        #set($inputString = "$inputString }")
    #end

    ## Check if the request context should be included as part of the execution input
    #if($requestContext && !$requestContext.empty)
        #set($inputString = "$inputString,")
        #set($inputString = "$inputString @@requestContext@@: $requestContext")
    #end
    
    #set($inputString = "$inputString}")
    #set($inputString = $inputString.replaceAll("@@",'"'))
    #set($len = $inputString.length() - 1)
    "input": "{$util.escapeJavaScript($inputString.substring(1,$len))}"
}

* The template is taken from the AWS Cloud Development Kit repo. It is part of the StepFunctionRestApi construct's implementation.