Java 使用XPath从XML获取元素值

我有如下XML文件：

<Invoice xmlns="urn:oasis:names:specification:ubl:schema:xsd:Invoice-2" xmlns:cac="urn:oasis:names:specification:ubl:schema:xsd:CommonAggregateComponents-2" xmlns:cbc="urn:oasis:names:specification:ubl:schema:xsd:CommonBasicComponents- xmlns:xades="http://uri.etsi.org/01903/v1.3.2#" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="urn:oasis:names:specification:ubl:schema:xsd:Invoice-2 UBL-Invoice-2.1.xsd">
<cac:AccountingSupplierParty>
<cac:Party>
  <cac:PartyIdentification>
    <cbc:ID schemeID="schema1">123231123</cbc:ID>
  </cac:PartyIdentification>
  <cac:PartyIdentification>
    <cbc:ID schemeID="schema2">2323232323</cbc:ID>
  </cac:PartyIdentification>
  <cac:PartyIdentification>
    <cbc:ID schemeID="schema3">4442424</cbc:ID>
  </cac:PartyIdentification>
  <cac:PostalAddress>
    <cbc:CityName>İstanbul</cbc:CityName>
    <cac:Country>
      <cbc:Name>Turkey</cbc:Name>
    </cac:Country>
  </cac:PostalAddress>
</cac:Party>
</cac:AccountingSupplierParty>
</Invoice>

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binaryXmlData是我的XML的源。首先，我将Base64二进制数据转换为xml。转换错误还是xpath实现错误？

您的代码和XML存在许多问题，包括：

您的XML格式不正确。

cbc

缺少命名空间前缀

Java代码从不定义

名称空间上下文

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另请参见

是否也在XPath表达式上设置了名称空间？

try {
    String decoded = new 
    String(DatatypeConverter.parseBase64Binary(binaryXmlData));
    DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
    dbf.setNamespaceAware(true);
    DocumentBuilder db = dbf.newDocumentBuilder();
    InputSource is = new InputSource(new StringReader(decoded));
    Document doc = db.parse(is);
    String expression = "/Invoice/cac:AccountingSupplierParty/cac:Party/cac:PartyIdentification/cbc:ID@[schemaID='schema2']/text()";    
    String schema2 = (String) xPath.compile(expression).evaluate(doc, XPathConstants.STRING);
    System.out.println(schema2);
    //schema2 is null

    //Above this code block returns correct value
    NodeList nl = doc.getElementsByTagName("cbc:CityName");
    System.out.println(nl.item(0).getTextContent());

} catch () {

}