VBA XML解析“对象变量或未设置块引用”

Question

我想在 MS Access 中使用 VBA 来读取某些 XML，但在解析此 XML 时出现“对象变量或未设置块引用”错误...

    <?xml version="1.0"?>
<GetCompetitivePricingForASINResponse xmlns="http://mws.amazonservices.com/schema/Products/2011-10-01">
    <GetCompetitivePricingForASINResult ASIN="B002L7HJAA" status="Success">
        <Product
            xmlns="http://mws.amazonservices.com/schema/Products/2011-10-01"
            xmlns:ns2="http://mws.amazonservices.com/schema/Products/2011-10-01/default.xsd">
            <Identifiers>
                <MarketplaceASIN>
                    <MarketplaceId>A1F83G8C2ARO7P</MarketplaceId>
                    <ASIN>B002L7HJAA</ASIN>
                </MarketplaceASIN>
            </Identifiers>
            <CompetitivePricing>
                <CompetitivePrices>
                    <CompetitivePrice belongsToRequester="false" condition="New" subcondition="New">
                        <CompetitivePriceId>1</CompetitivePriceId>
                        <Price>
                            <LandedPrice>
                                <CurrencyCode>GBP</CurrencyCode>
                                <Amount>14.45</Amount>
                            </LandedPrice>
                        </Price>
                    </CompetitivePrice>
                </CompetitivePrices>
            </CompetitivePricing>
        </Product>
    </GetCompetitivePricingForASINResult>
</GetCompetitivePricingForASINResponse>

使用此代码...

Public Function READXML()

Dim objXMLNode1 As MSXML2.IXMLDOMNodeList

Set objXMLDoc = New MSXML2.DOMDocument60

objXMLDoc.loadXML ("C:\Users\LW\Desktop\formatted.xml")

XmlNamespaces = "xmlns:ns2='http://mws.amazonservices.com/schema/Products/2011-10-01/default.xsd' xmlns:ns1='http://mws.amazonservices.com/schema/Products/2011-10-01'"

objXMLDoc.SetProperty "SelectionNamespaces", XmlNamespaces

Set objXMLNode1 = objXMLDoc.selectSingleNode("//ns2:Price/ns2:LandedPrice/ns2:Amount")

MsgBox objXMLNode1(0).text

End Function

如您所见，我试图提取 XML 值（在 XML 中显示为 14.45）

我在谷歌上搜索了很长时间都无济于事，但是在阅读了'SelectSingleNode' XPath query from XML with multiple Namespaces之后，我选择了上面的代码

任何想法为什么我会收到错误？

Answer 1

XPath 中提到的 XML 元素位于以下默认命名空间中：

xmlns="http://mws.amazonservices.com/schema/Products/2011-10-01"

除了其他答案中提供的一些好的建议之外，您应该使用 ns1 前缀，您已在 XPath 中声明引用默认命名空间：

XmlNamespaces = "xmlns:ns2='http://mws.amazonservices.com/schema/Products/2011-10-01/default.xsd' xmlns:ns1='http://mws.amazonservices.com/schema/Products/2011-10-01'"

objXMLDoc.SetProperty "SelectionNamespaces", XmlNamespaces

Set objXMLNode1 = objXMLDoc.selectSingleNode("//ns1:Price/ns1:LandedPrice/ns1:Amount")

Answer 2

目前，您的代码存在几个问题：

1. 未声明 objXMLDoc 和 XmlNamespaces。
2. LoadXML() 用于 xml 字符串，Load() 用于外部文件。
3. 当标签当前没有这样的前缀时，您在 xpath 查询表达式中使用命名空间 ns2。
4. 您声明IXMLDOMNodeList 对象但使用selectSingleNode() 方法并另外使用文本值的列表索引。这会引发类型不匹配错误。
5. 对于使用 MSXML v6.0 的未声明命名空间，您必须声明命名空间并在 xpath 表达式中引用它。

考虑下面使用NodeList()的调整代码：

Public Function READXML()
    Dim objxmldoc As New MSXML2.DOMDocument60
    Dim objXMLNode1 As MSXML2.IXMLDOMNodeList
    Dim xmlNamespaces As String

    objxmldoc.Load ("C:\Users\LW\Desktop\formatted.xml")
    xmlNamespaces = "xmlns:ns2='http://mws.amazonservices.com/schema/Products/2011-10-01/default.xsd' " _
                      & "xmlns:ns1='http://mws.amazonservices.com/schema/Products/2011-10-01'"

    objxmldoc.setProperty "SelectionNamespaces", xmlNamespaces
    Set objXMLNode1 = objxmldoc.SelectNodes("//ns1:Price/ns1:LandedPrice/ns1:Amount")

    MsgBox objXMLNode1(0).Text

    Set objxmldoc = Nothing

End Function

或者，使用SelectSingleNode() 方法：

Public Function READXML()
    Dim objxmldoc As New MSXML2.DOMDocument60
    Dim objXMLNode1 As MSXML2.IXMLDOMElement
    Dim xmlNamespaces As String

    objxmldoc.Load ("C:\Users\LW\Desktop\formatted.xml")
    xmlNamespaces = "xmlns:ns2='http://mws.amazonservices.com/schema/Products/2011-10-01/default.xsd' " _
                          & "xmlns:ns1='http://mws.amazonservices.com/schema/Products/2011-10-01'"

    objxmldoc.setProperty "SelectionNamespaces", xmlNamespaces
    Set objXMLNode1 = objxmldoc.SelectSingleNode("//ns1:Price/ns1:LandedPrice/ns1:Amount")        

    MsgBox objXMLNode1.Text

    Set objxmldoc = Nothing

End Function