PowerShell中使用Invoke-WebRequest传递变量时报错问题排查

问题场景 #

无硬编码值的脚本可正常运行：

$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"}'

但使用变量替换时出现两类错误：

1. 找不到接受参数的位置参数：双引号包裹JSON时，未转义内部双引号导致PowerShell错误解析参数边界

# 错误示例
$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}"

2. 无效字符'$'，寻找值的起始位置：单引号包裹JSON时，PowerShell不会解析内部变量，导致JSON中直接出现$Variable字符串，破坏JSON格式

# 错误示例
$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}'

解决方案 #

方案1：使用对象转JSON（推荐） #

通过创建PowerShell对象映射API请求结构，再转换为JSON字符串，彻底避免引号和格式问题：

$headers = @{}
$headers.Add("accept", "application/json")
$headers.Add("content-type", "application/json")
$headers.Add("authorization", "$APIToken")

# 定义业务变量（替换为实际值）
$QuantityLiters = "676.8"
$FuelType = "Diesel"
$StationAddress = "350 Rhode Island St, San Francisco, CA 94103"
$TransactionSale = "640.2"
$Currency = "usd"
$TransactionID = "5454534"
$TransactionDateTime = "2024-02-22T10:20:50.52-06:00"
$Vehicle = "570"

# 构建请求体对象，完全匹配API要求的结构
$fuelPurchaseBody = [PSCustomObject]@{
    fuelQuantityLiters = $QuantityLiters
    iftaFuelType = $FuelType
    transactionLocation = $StationAddress
    transactionPrice = [PSCustomObject]@{
        amount = $TransactionSale
        currency = $Currency
    }
    transactionReference = $TransactionID
    transactionTime = $TransactionDateTime
    vehicleId = $Vehicle
}

# 转换为JSON字符串（-Depth 3确保嵌套对象被正确转换）
$jsonBody = $fuelPurchaseBody | ConvertTo-Json -Depth 3

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

方案2：手动转义引号并插值 #

如果需要直接拼接字符串，需用反引号`转义JSON内部的双引号，同时为字符串类型变量添加引号：

$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""}"

API说明（中文翻译） #

Samsara燃油交易提交API要求请求体包含以下必填字段：

• fuelQuantityLiters：燃油购买量（单位：升）
• iftaFuelType：燃油类型（例如Diesel）
• transactionLocation：交易地点地址
• transactionPrice：嵌套对象，包含交易金额amount和货币代码currency（例如usd）
• transactionReference：交易唯一参考ID
• transactionTime：交易时间（需符合ISO 8601格式，如2024-02-22T10:20:50.52-06:00）
• vehicleId：本次加油关联的车辆ID

内容的提问来源于stack exchange，提问作者JamesD