Trial #43: Paging OData with PowerShell

Problem:

If you want to explore or utilise an OData API in PowerShell without any extra dependencies it is quite easy using just Invoke-WebRequest to acquire the response and ConvertFrom-Json to parse it into easy to handle PSCustomObjects.

For example:

Invoke-WebRequest https://services.odata.org/TripPinRESTierService/People  |
            Select-Object -ExpandProperty Content | 
            ConvertFrom-Json |
            Select-Object -ExpandProperty value

However, if the endpoint has server-driven paging you will not get all of the available values with such a basic approach as you will simply get the first page of values.

Solution:

In order to demonstrate this solution I split the unpaged response from the TripPinRESTierService into 20 files, the first 19 with the control information annotation @odata.nextLink.

If we start with the first file we can then iterate through the remaining pages until there the sequence is broken or ended.

$url = "https://it-trials.craigchamberlain.it/assets/images/43/0.json"

while($url){
    $odata = 
        Invoke-WebRequest $url  |
            Select-Object -ExpandProperty Content | 
            ConvertFrom-Json
    
    $url = $odata."@odata.nextLink"
    $odata.value
}

It would be nice to check for html status codes and perhaps have some retries but this intended to be the minimum viable solution. I intend look at more comprehensive solutions including the Command Export-ODataEndpointProxy in a future post. Unfortunately, this tool seems to be limited to OData versions 1.0-3.0 and may need some maintenance in order to process the TripPinRESTierService (OData 4.0). I will investigate using a .NET client library to achieve something similar.