Azure Question posted in
The official documentation to get you started can be found here.

Azure – How to access a nested JSON field in PowerShell

I’m trying to access a specific field in a JSON object created by Azure Advisor using PowerShell. I have the following object:

@{id=/subscriptions/xxxx/providers/Microsoft.Advisor/recommendations/xxxx;
category=Cost;
impact=High;
impactedArea=Microsoft.Subscriptions/subscriptions;
description=Consider virtual machine reserved instance to save over your on-demand costs;
recommendationText=Consider virtual machine reserved instance to save over your on-demand costs;
recommendationTypeId=xxx; instanceName=xxxx;
additionalInfo=;
tags=;
ResourceId=/subscriptions/xxxx/providers/Microsoft.Advisor/recommendations/xxxx}

In this, I want to access a field ‘savingsCurrency’ to compare in an if-statement. The field is nested in ‘additionalInfo’, which in turn is in the ‘advisorRecommendation’ object.

I have the following code now:

Write-Output "advisorrecommendation: $advisorRecommendation"

if (-not([string]::IsNullOrEmpty($advisorRecommendation.additionalInfo)))
{
    $additionalInfo = $advisorRecommendation.additionalInfo | ConvertTo-Json
    Write-Output "additionalInfo: $additionalInfo"
    if (-not([string]::IsNullOrEmpty($additionalInfo.savingsCurrency)))
    {
        $savingsCurrency = $additionalInfo.savingsCurrency | ConvertTo-Json
        Write-Output "Currency: $savingsCurrency"
    }
}
else
{
    $additionalInfo = $null
}

This code gives me the following outputs:

advisorrecommendation:
@{id=/subscriptions/xxxx/providers/Microsoft.Advisor/recommendations/xxx; category=Cost; impact=High; impactedArea=Microsoft.Subscriptions/subscriptions; description=Consider virtual machine reserved instance to save over your on-demand costs; recommendationText=Consider virtual machine reserved instance to save over your on-demand costs; recommendationTypeId=xxxx; instanceName=xxxx; additionalInfo=; tags=; ResourceId=/subscriptions/xxxx/providers/Microsoft.Advisor/recommendations/xxxx}

additionalInfo: {
    "annualSavingsAmount": "697",
    "reservedResourceType": "virtualmachines",
    "targetResourceCount": "4",
    "savingsCurrency": "USD",
    "savingsAmount": "58",
    "lookbackPeriod": "30",
    "displaySKU": "Standard_B2s",
    "displayQty": "4",
    "location": "westeurope",
    "region": "westeurope",
    "vmSize": "Standard_B2s",
    "subId": "xxxx",
    "scope": "Single",
    "term": "P1Y",
    "qty": "4",
    "sku": "Standard_B2s"
}

The ‘savingsCurrency’ field never passes the null/empty check, even though I can clearly see that the field in ‘additionalInfo’ is not empty or null. What is going wrong here? If I try the print without the preceeding existence check, it simply prints the additionalInfo object with .savingsCurrency appended like this:

savingsCurrency: {
    "annualSavingsAmount": "697",
    "reservedResourceType": "virtualmachines",
    "targetResourceCount": "4",
    "savingsCurrency": "USD",
    "savingsAmount": "58",
    "lookbackPeriod": "30",
    "displaySKU": "Standard_B2s",
    "displayQty": "4",
    "location": "westeurope",
    "region": "westeurope",
    "vmSize": "Standard_B2s",
    "subId": "xxxx",
    "scope": "Single",
    "term": "P1Y",
    "qty": "4",
    "sku": "Standard_B2s"
}.savingsCurrency
Tags:

2

Answers


  1. 0

    $advisorRecommendation.additionalInfo is an object with nested properties:

    $advisorRecommendation.additionalInfo.savingsCurrency
# USD

    but $additionalInfo is a string because you’ve converted the object to json before assigning it:

    $additionalInfo = $advisorRecommendation.additionalInfo | ConvertTo-Json

$additionalInfo.GetType().FullName
# System.String

    As a result, $savingsCurrency = $additionalInfo.savingsCurrency is trying to read the savingsCurrency property of a string, and strings don’t have that property so you get $null.

    What you want to do instead is keep a reference to the $advisorRecommendation.additionalInfo object instead and only convert it to json for the purpose of writing it to the console:

    Write-Output "advisorrecommendation: $advisorRecommendation"

#   vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
if ($advisorRecommendation.additionalInfo -ne $null)
#   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
{

    # vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
    $additionalInfo = $advisorRecommendation.additionalInfo
    Write-Output "additionalInfo: $($additionalInfo | ConvertTo-Json -Depth 99)"
    # ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

    if (-not([string]::IsNullOrEmpty($additionalInfo.savingsCurrency)))
    {
        $savingsCurrency = $additionalInfo.savingsCurrency
        Write-Output "Currency: $savingsCurrency"
    }
}
else
{
    $additionalInfo = $null
}

    You should now see Currency: USD in your output.

    Note that $additionalInfo.savingsCurrency is already a string so you don’t need to use ConvertTo-Json to display the value unless you specifically want it to be formatted as a json string (i.e. "USD" with surrounding quotes and any special characters like escaped, instead of the literal string value USD)

    Login or Signup to reply.
  2. 0

    The ‘savingsCurrency’ field never passes the null/empty check, even though I can clearly see that the field in ‘additionalInfo’ is not empty or null. What is going wrong here?

    You can check not null and if condition like below:

    $additionalInfo = $additionalInfo | ConvertFrom-Json
if (-not([string]::IsNullOrEmpty($additionalInfo.savingsCurrency)))
    {
        $savingsCurrency = $additionalInfo.savingsCurrency | ConvertTo-Json
        Write-Output "Currency: $savingsCurrency"
    }

    enter image description here

    How to access JSON field in PowerShell

    To access any json filed you need to first convert it from json like below :

    $additionalInfo = $additionalInfo | ConvertFrom-Json
$savingsCurrency= $savingsCurrency | ConvertFrom-Json

    To access any field you can use dot operator:

    $additionalInfo.savingsCurrency

    enter image description here

    Login or Signup to reply.
Please signup or login to give your own answer.

Back To Top
Search