使用 ConvertFrom-Json 处理 JSON 引用

Question

默认情况下，PowerShell 的 ConvertFrom-Json cmdlet 似乎不处理 JSON 文档中的引用。

{
    "foo": {"$ref": "#/bar"},
    "bar": true
}

我真的不知道这个 JSON 规范的官方状态（参见 here 和 here），但是有没有办法在 PowerShell 中管理这样的事情？

Answer 1

AFAIK 没有内置的方法来解析 JSON 引用。我通常会寻找 C# 解决方案来解决 PowerShell 中不支持的问题，因为这些解决方案大多数时候都可以转换为 PowerShell 代码，但我找不到在没有自定义代码的情况下在 C# 中执行此操作的简单方法。

所以我认为您可能需要自己编写一些函数并使用Invoke-Expression 和引用类型（转换后的对象是 PSCustomObject）来帮助您。

概念证明（包含许多错误）：

$json = @'
{
    "foo": {"$ref": "#/bar"},
    "bar": true
}
'@

$t = ConvertFrom-Json -InputObject $json

Write-Host "Before"
$t | Out-Host

function resolveReferences ($obj) {

    #Loop through propeties    
    $obj.psobject.Properties | ForEach-Object {

        #ref-values are PSCustomObjects with a $ref-property, so let's find the PSCustomObjects
        if ($_.TypeNameOfValue -eq 'System.Management.Automation.PSCustomObject') {

            #Verify it was a ref-value by checking for $ref-property
            if ($_.Value.'$ref') { 
                #Convert value to powershell-path like $t.foo
                $refpath = $_.Value.'$ref'.Replace("#/",'$t.').Replace("/",".")

                #Execute generated powershell-path to get the referenced object and replace reference with the referenced object
                $_.Value = (Invoke-Expression -Command $refpath)
            }
        }
    }

}

resolveReferences -obj $t

Write-host "After"
$t | Out-Host

输出：

Before

foo            bar
---            ---
@{$ref=#/bar} True


After

 foo  bar
 ---  ---
True True

您可以根据自己的需要进行扩展。前任。支持对象数组：

$json = @'
{
    "foo": {"$ref": "#/bar"},
    "fooarray": [
        {"item": {"$ref": "#/bar"}},
        {"item": {"$ref": "#/hello"}}
    ],
    "test": [1,2,3],
    "bar": true,
    "hello": "world"
}
'@

$t = ConvertFrom-Json -InputObject $json

Write-Host "Before"
$t | Out-Host

function resolveReferences ($obj) {

    $obj.psobject.Properties | ForEach-Object {
        if ($_.TypeNameOfValue -eq 'System.Management.Automation.PSCustomObject') {
            if ($_.Value.'$ref') {
                $refpath = $_.Value.'$ref'.Replace("#/",'$t.').Replace("/",".")
                $_.Value = (Invoke-Expression -Command $refpath)
            }
        } elseif ($_.TypeNameOfValue -eq 'System.Object[]') {
            #If array, loop through objects (recursive search)
            $_.Value | ForEach-Object { resolveReferences -obj $_ }
        }
    }

}

resolveReferences -obj $t

Write-host "After"
$t | Out-Host

输出：

#item properties in fooarray-objects are ref paths, it's just PS being to lazy to go deeper and show their values

Before    

foo      : @{$ref=#/bar}
fooarray : {@{item=}, @{item=}}
test     : {1, 2, 3}
bar      : True
hello    : world


After

foo      : True
fooarray : {@{item=True}, @{item=world}}
test     : {1, 2, 3}
bar      : True
hello    : world