如何用PowerShell 5.1验证包含内联Schema的XML？

我创建了包含内联Schema的XML文件，并编写PowerShell脚本验证它，但每次都失败。不确定问题出在XML还是验证脚本——我复制了微软的inline-namespaced.xml示例，用LINQ to XML脚本验证显示有效，但把book元素重命名为Schema未定义的books后，脚本仍显示有效！查相关问题得知，当Schema的targetNamespace和文档不匹配时，LINQ to XML会默认通过验证。于是我改用XmlReader写脚本，但还是无法验证微软的基础示例，提示：Line 2, Pos 2, Could not find schema information for the element 'catalog'，连根元素都报错。显然操作有误，但问题到底出在哪？

inline-namespaced.xml #

<?xml version="1.0"?>
<catalog xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:x="urn:book">
  <!-- START OF SCHEMA -->
  <xsd:schema targetNamespace="urn:book">
    <xsd:element name="book">
      <xsd:complexType>
        <xsd:sequence>
          <xsd:element name="author" type="xsd:string"/>
          <xsd:element name="title" type="xsd:string"/>
          <xsd:element name="genre" type="xsd:string"/>
          <xsd:element name="price" type="xsd:float"/>
          <xsd:element name="publish_date" type="xsd:date"/>
          <xsd:element name="description" type="xsd:string"/>
        </xsd:sequence>
        <xsd:attribute name="id" type="xsd:string"/>
      </xsd:complexType>
    </xsd:element>
  </xsd:schema>
  <!-- END OF SCHEMA -->
  <x:book id="bk101">
    <author>Gambardella, Matthew</author>
    <title>XML Developer's Guide</title>
    <genre>Computer</genre>
    <price>44.95</price>
    <publish_date>2000-10-01</publish_date>
    <description>An in-depth look at creating applications with XML.</description>
  </x:book>
</catalog>

使用XmlReader的PowerShell 5.1脚本 #

# Load the XML content
$xmlFile = "C:\Temp\inline-namespaced.xml"

# Prepare the event handler for validation errors
$eventHandler = {
    param ($sender, $eventArgs)
    Write-Host $("Line {0}, Pos {1}, {2}" -f $eventArgs.Exception.LineNumber, $eventArgs.Exception.LinePosition, $eventArgs.Exception.Message)
}

# Create XmlReaderSettings and enable schema validation
$settings = New-Object System.Xml.XmlReaderSettings
$settings.ValidationType = [System.Xml.ValidationType]::Schema
$settings.ValidationFlags =
    [System.Xml.Schema.XmlSchemaValidationFlags]::ProcessInlineSchema -bor
    [System.Xml.Schema.XmlSchemaValidationFlags]::ReportValidationWarnings

# Attach the event handler
$settings.add_ValidationEventHandler($eventHandler)

# Create the XmlReader with the settings
$reader = [System.Xml.XmlReader]::Create($xmlFile, $settings)

# Read through the XML content to trigger validation
while ($reader.Read()) { }

$reader.Close()

核心问题1：根元素catalog无Schema约束 #

你的内联Schema只定义了urn:book命名空间下的book元素，根元素catalog属于无命名空间，没有任何Schema对它进行约束，所以XmlReader会提示找不到该元素的Schema信息。这是正常警告，若目标仅验证x:book元素，可忽略该警告；若要验证整个文档，需给根元素添加Schema定义。

核心问题2：LINQ to XML验证失效的原因 #

LINQ to XML默认不强制要求元素必须匹配Schema，仅当明确指定验证规则时才会严格检查。当你把x:book改成x:books时，由于没有Schema定义该元素，本该报错，但LINQ to XML默认不校验无匹配Schema的元素，因此误判为有效。

修正后的验证方案 #

方案1：忽略根元素警告，专注验证x:book #

修改脚本的事件处理器，过滤掉根元素catalog的警告，只处理错误和book相关的警告：

$xmlFile = "C:\Temp\inline-namespaced.xml"

$eventHandler = {
    param ($sender, $eventArgs)
    # 过滤catalog元素的无Schema警告
    if ($eventArgs.Severity -eq [System.Xml.Schema.ValidationSeverity]::Error -or 
        ($eventArgs.Severity -eq [System.Xml.Schema.ValidationSeverity]::Warning -and 
         $eventArgs.Exception.Message -notlike "*catalog*")) {
        Write-Host $("Line {0}, Pos {1}, {2}" -f $eventArgs.Exception.LineNumber, $eventArgs.Exception.LinePosition, $eventArgs.Exception.Message)
    }
}

$settings = New-Object System.Xml.XmlReaderSettings
$settings.ValidationType = [System.Xml.ValidationType]::Schema
$settings.ValidationFlags =
    [System.Xml.Schema.XmlSchemaValidationFlags]::ProcessInlineSchema -bor
    [System.Xml.Schema.XmlSchemaValidationFlags]::ReportValidationWarnings

$settings.add_ValidationEventHandler($eventHandler)

$reader = [System.Xml.XmlReader]::Create($xmlFile, $settings)

while ($reader.Read()) { }

$reader.Close()

此时将x:book改为x:books，脚本会触发明确的错误提示，指出books元素未被Schema定义。

方案2：给根元素添加Schema约束 #

若要验证整个XML文档，修改内联Schema，添加对无命名空间catalog元素的定义：

<?xml version="1.0"?>
<catalog xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:x="urn:book">
  <!-- START OF SCHEMA -->
  <xsd:schema targetNamespace="urn:book" xmlns:xsd="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified">
    <!-- 定义无命名空间的catalog元素 -->
    <xsd:element name="catalog" xmlns="">
      <xsd:complexType>
        <xsd:sequence>
          <!-- 允许内联Schema元素 -->
          <xsd:element ref="xsd:schema" minOccurs="0"/>
          <!-- 引用urn:book命名空间的book元素 -->
          <xsd:element ref="x:book"/>
        </xsd:sequence>
      </xsd:complexType>
    </xsd:element>
    
    <!-- 原有的book元素定义 -->
    <xsd:element name="book">
      <xsd:complexType>
        <xsd:sequence>
          <xsd:element name="author" type="xsd:string"/>
          <xsd:element name="title" type="xsd:string"/>
          <xsd:element name="genre" type="xsd:string"/>
          <xsd:element name="price" type="xsd:float"/>
          <xsd:element name="publish_date" type="xsd:date"/>
          <xsd:element name="description" type="xsd:string"/>
        </xsd:sequence>
        <xsd:attribute name="id" type="xsd:string"/>
      </xsd:complexType>
    </xsd:element>
  </xsd:schema>
  <!-- END OF SCHEMA -->
  <x:book id="bk101">
    <author>Gambardella, Matthew</author>
    <title>XML Developer's Guide</title>
    <genre>Computer</genre>
    <price>44.95</price>
    <publish_date>2000-10-01</publish_date>
    <description>An in-depth look at creating applications with XML.</description>
  </x:book>
</catalog>

修改后，XmlReader会验证整个文档，包括根元素和x:book，修改book为books时会直接报错。

内容的提问来源于stack exchange，提问作者Wim