API gateway request modification into step function request.

Question

#set($allParams = $input.params())
{
"body-json" : $input.json('$'),
"params" : {
#foreach($type in $allParams.keySet())
    #set($params = $allParams.get($type))
"$type" : {
    #foreach($paramName in $params.keySet())
    "$paramName" : "$util.escapeJavaScript($params.get($paramName))"
        #if($foreach.hasNext),#end
    #end
}
    #if($foreach.hasNext),#end
#end
},
"stage-variables" : {
#foreach($key in $stageVariables.keySet())
"$key" : "$util.escapeJavaScript($stageVariables.get($key))"
    #if($foreach.hasNext),#end
#end
},
"context" : {
    "account-id" : "$context.identity.accountId",
    "api-id" : "$context.apiId",
    "api-key" : "$context.identity.apiKey",
    "authorizer-principal-id" : "$context.authorizer.principalId",
    "caller" : "$context.identity.caller",
    "cognito-authentication-provider" : "$context.identity.cognitoAuthenticationProvider",
    "cognito-authentication-type" : "$context.identity.cognitoAuthenticationType",
    "cognito-identity-id" : "$context.identity.cognitoIdentityId",
    "cognito-identity-pool-id" : "$context.identity.cognitoIdentityPoolId",
    "http-method" : "$context.httpMethod",
    "stage" : "$context.stage",
    "source-ip" : "$context.identity.sourceIp",
    "user" : "$context.identity.user",
    "user-agent" : "$context.identity.userAgent",
    "user-arn" : "$context.identity.userArn",
    "request-id" : "$context.requestId",
    "resource-id" : "$context.resourceId",
    "resource-path" : "$context.resourcePath"
    }
}

How do i send all these fields into step function input key.

I have tried every way it does not work.

currently I am only able to send below request.

#set($data='{ "context" : {"account-id" : "'+$context.identity.accountId+'","api-id" : "'+$context.apiId+'","api-key" : "'+$context.identity.apiKey+'","authorizer-principal-id" : "'+$context.authorizer.principalId+'","caller" : "'+$context.identity.caller+'","cognito-authentication-provider" : "'+$context.identity.cognitoAuthenticationProvider+'","cognito-authentication-type" : "'+$context.identity.cognitoAuthenticationType+'","cognito-identity-id" : "'+$context.identity.cognitoIdentityId+'","cognito-identity-pool-id" : "'+$context.identity.cognitoIdentityPoolId+'","http-method" : "'+$context.httpMethod+'","stage" : "'+$context.stage+'","source-ip" : "'+$context.identity.sourceIp+'","user" : "'+$context.identity.user+'","user-agent" : "'+$context.identity.userAgent+'","user-arn" : "'+$context.identity.userArn+'","request-id" : "'+$context.requestId+'","resource-id" : "'+$context.resourceId+'","resource-path" : "'+$context.resourcePath+'"}, "body" :'+$input.json('$')+'}')
#set($data=$util.escapeJavaScript($data))
{
  "input" :"$data",
  "stateMachineArn": "my-state-machine-arn"
}

Thanks for any help.

Accepted Answer

I was able to find a solution for this.

I found it on stackoverflow, here is the link to the answer [https://stackoverflow.com/a/71195539](Link)

Below is the Template
```
## 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 = "{@@account-id@@:@@$context.identity.accountId@@,@@api-id@@:@@$context.apiId@@,@@api-key@@:@@$context.identity.apiKey@@,@@authorizer-principal-id@@: @@$context.authorizer.principalId@@,@@caller@@:@@$context.identity.caller@@,@@cognito-authentication-provider@@: @@$context.identity.cognitoAuthenticationProvider@@,@@cognito-authentication-type@@:@@$context.identity.cognitoAuthenticationType@@,@@cognito-identity-id@@: @@$context.identity.cognitoIdentityId@@,@@cognito-identity-pool-id@@:@@$context.identity.cognitoIdentityPoolId@@,@@http-method@@:@@$context.httpMethod@@,@@stage@@: @@$context.stage@@,@@source-ip@@:@@$context.identity.sourceIp@@,@@user@@:@@$context.identity.user@@,@@user-agent@@:@@$context.identity.userAgent@@,@@user-arn@@: @@$context.identity.userArn@@,@@request-id@@:@@$context.requestId@@,@@resource-id@@:@@$context.resourceId@@,@@resource-path@@:@@$context.resourcePath@@}")

#set($inputString = '')
#set($allParams = $input.params())
{
    "stateMachineArn": "my-state-machine-arn",

#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 @@context@@: $requestContext")
    #end
    
    #set($inputString = "$inputString}")
    #set($inputString = $inputString.replaceAll("@@",'"'))
    #set($len = $inputString.length() - 1)
    "input": "{$util.escapeJavaScript($inputString.substring(1,$len))}"
}
```

Answer

Hi Abhay,

How about serializing entire request context, parameters, stage variables, and body into a single JSON object? This involves dynamically constructing a JSON string that incorporates all parts of the request. Below is an example which captures everything: capture everything: the context, stage variables, parameters (query string parameters, path parameters, and headers), and the request body:

```
#set($allParams = $input.params())
#set($contextMap = {
  "account-id" : "$context.identity.accountId",
  "api-id" : "$context.apiId",
  "api-key" : "$context.identity.apiKey",
  "authorizer-principal-id" : "$context.authorizer.principalId",
  "caller" : "$context.identity.caller",
  "cognito-authentication-provider" : "$context.identity.cognitoAuthenticationProvider",
  "cognito-authentication-type" : "$context.identity.cognitoAuthenticationType",
  "cognito-identity-id" : "$context.identity.cognitoIdentityId",
  "cognito-identity-pool-id" : "$context.identity.cognitoIdentityPoolId",
  "http-method" : "$context.httpMethod",
  "stage" : "$context.stage",
  "source-ip" : "$context.identity.sourceIp",
  "user" : "$context.identity.user",
  "user-agent" : "$context.identity.userAgent",
  "user-arn" : "$context.identity.userArn",
  "request-id" : "$context.requestId",
  "resource-id" : "$context.resourceId",
  "resource-path" : "$context.resourcePath"
})
#set($stageVariables = $context.stageVariables)
#set($body = $input.json('$'))

#set($inputObject = {
  "context" : $util.toJson($contextMap),
  "stage-variables" : $util.toJson($stageVariables),
  "params" : $util.toJson($allParams),
  "body" : $body
})

#set($inputString = $util.toJson($inputObject))
{
  "input": "$util.escapeJavaScript($inputString)",
  "stateMachineArn": "my-state-machine-arn"
}

```
This script does the following:
Constructs a map for the context and stage variables.
Uses $input.params() to gather all parameters (query string, path, headers) automatically.
Serializes the context, stage variables, parameters, and body into a JSON object.
Converts the entire JSON object into a string to be used as the input for the Step Function.
Make sure to replace "my-state-machine-arn" with the actual ARN of your state machine.

Hope this helps!

API gateway request modification into step function request.

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