Call REST API from PowerShell Script

Question

How can I call a rest based API from a PowerShell script and process the Json answer?

Answer 1

What you want is PowerShell 3 and its Invoke-RestMethod, ConvertTo-Json, and ConvertFrom-Json cmdlets. Your code will end up looking like:

 $stuff = Invoke-RestMethod -Uri $url -Method Get;

and there shouldn't even be a need to invoke ConvertFrom-Json on the resulting $stuff => it's already in a usable non-string format.

See http://technet.microsoft.com/en-us/Library/hh849971.aspx for details.

Answer 2

I created this Get-Http function to make HTTP requests

param([string]$url)

$req = [System.Net.WebRequest]::Create($url)
$req.Method ="GET"
$req.ContentLength = 0

$resp = $req.GetResponse()
$reader = new-object System.IO.StreamReader($resp.GetResponseStream())
$reader.ReadToEnd()

Dealing with the end result as xml is really easy, however, if you want to process JSON you probably will need some .Net library like JSON.Net.

Answer 3

We use Powershell to query a REST API that deals only with Json style data. It was awkward at first but the below code is all we need to perform most operations:

# Authentication
$webclient = New-Object System.Net.WebClient
$creds = New-Object System.Net.NetworkCredential("MyUsername","MyPassword");
$webclient.Credentials = $creds

# Data prep
$data = @{Name='Test';} | ConvertTo-Json

# GET
$webClient.DownloadString($url) | ConvertFrom-Json

# POST
$webClient.UploadString($url,'POST',$data)

# PUT
$webClient.UploadString($url,'PUT',$data)