Json - Powershell: Using Invoke-WebRequest with variables

JamesD
February 22, 2024
178 views
0 votes
2 Answers

I am currently having a problem with a script to send fuel transactions through an api. It works without variables:

$headers=@{}
$headers.Add("accept", "application/json")
$headers.Add("content-type", "application/json")
$headers.Add("authorization", "$APIToken")
$response = Invoke-WebRequest -Uri 'https://api.samsara.com/fuel-purchase' -Method POST -Headers $headers -ContentType 'application/json' -Body '{"fuelQuantityLiters":"676.8","iftaFuelType":"Diesel","transactionLocation":"350 Rhode Island St, San Francisco, CA 94103","transactionPrice":{"amount":"640.2","currency":"usd"},"transactionReference":"5454534","transactionTime":"2024-02-22T10:20:50.52-06:00","vehicleId":"570"}'

But, with variables I get errors.

# A POSITIONAL PARAMETER CANNOT BE FOUND THAT ACCEPTS ARGUMENT ("" Around Body)
$response = Invoke-WebRequest -Uri 'https://api.samsara.com/fuel-purchase' -Method POST -Headers $headers -ContentType 'application/json' -Body "{"fuelQuantityLiters":$QuantityLiters,"iftaFuelType":$FuelType,"transactionLocation":$StationAddress,"transactionPrice":{"amount":$TransactionSale,"currency":$Currency},"transactionReference":$TransactionID,"transactionTime":$TransactionDateTime,"vehicleId":$Vehicle}"

# INVALID CHARACTER '$' LOOKING FOR BEGINNING OF VALUE ('' Around Body)
$response = Invoke-WebRequest -Uri 'https://api.samsara.com/fuel-purchase' -Method POST -Headers $headers -ContentType 'application/json' -Body '{"fuelQuantityLiters":$QuantityLiters,"iftaFuelType":$FuelType,"transactionLocation":$StationAddress,"transactionPrice":{"amount":$TransactionSale,"currency":$Currency},"transactionReference":$TransactionID,"transactionTime":$TransactionDateTime,"vehicleId":$Vehicle}'

I figure it has to do with the quotations, but I’m not sure where I need to fix it. Here is the page with the api details about what I’m doing:
https://developers.samsara.com/reference/postfuelpurchase

Tags: json powershell

Answers

You could try constructing the request-body JSON from a hastable like this –

$fuelQuantityLiters   = 676.8
$iftaFuelType         = "Diesel"
$transactionLocation  = "350 Rhode Island St, San Francisco, CA 94103"
$amount               = 676.8
$currency             = "usd"
$transactionReference = "5454534"
$transactionTime      = "2024-02-22T10:20:50.52-06:00"
$vehicleId            = 570

$tranJSON = @{}
$tranJSON.add("amount",   $amount)
$tranJSON.add("currency", $currency)

$restJSON = @{}
$restJSON.add("fuelQuantityLiters",  $fuelQuantityLiters)
$restJSON.add("iftaFuelType",        $iftaFuelType)
$restJSON.add("transactionLocation", $transactionLocation)
$restJSON.add("transactionPrice",    $tranJSON)
$restJSON.add("transactionReference",$transactionReference)
$restJSON.add("transactionTime",     $transactionTime)
$restJSON.add("vehicleId",           $vehicleId)

$JSON = $restJSON | ConvertTo-JSON -compress

That yields the JSON your after for the request body, then pass that to the API

$response = Invoke-WebRequest -Uri 'https://api.samsara.com/fuel-purchase' -Method POST -Headers $headers -ContentType 'application/json' -Body $JSON

In general, I find it is better to define everything ahead of time and just pass variables as parameters to Invoke-WebRequest.

I don’t have your situation to test this, but below is code similar to what I’ve been using for our own servers:

$uri = 'https://api.samsara.com/fuel-purchase'
$contentType = "application/json"
$headers = @{
   accept = $contentType
   "content-type" = $contentType
   authorization = "$APIToken"
}
$body = @{
   fuelQuantityLiters   = $QuantityLiters
   iftaFuelType         = $FuelType
   transactionLocation  = $StationAddress
   transactionPrice     = @{
      amount   = $TransactionSale
      currency = $Currency
   }
   transactionReference = $TransactionID
   transactionTime      = $TransactionDateTime
   vehicleId            = $Vehicle
} | ConvertTo-Json
$response = Invoke-WebRequest -Uri $uri -Method POST -Headers $headers -ContentType $contentType -Body $body

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Json – Powershell: Using Invoke-WebRequest with variables

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