java - 在 Java 中检索节点的 XPathExpression 是否正确？

Question

我有一个 XML 文档，其中包含多个 hpp:HourlyHistoricalPrice 元素，如下所示:

<?xml version="1.0">
<hhp:HourlyHistoricalPrices xmlns:hhp="urn:or-HourlyHistoricalPrices">
  <hhp:HourlyHistoricalPrice xmlns:hhp="urn:or-HourlyHistoricalPrice">
    <hhp:indexId>1025127</hhp:indexId>
    <hhp:resetDate>20161231T000000</hhp:resetDate>
    <hhp:refSource>AIBO</hhp:refSource>
    <hhp:indexLocation/>
    <hhp:price1>50,870000</hhp:price1>
    ...
    <hhp:price48>43,910000</hhp:price48>
  </hhp:HourlyHistoricalPrice>
  <hhp:HourlyHistoricalPrice xmlns:hhp="urn:or-HourlyHistoricalPrice">
    <hhp:indexId>1025127</hhp:indexId>
    <hhp:resetDate>20160101T000000</hhp:resetDate>
    <hhp:refSource>AIBO</hhp:refSource>
    <hhp:indexLocation/>
    <hhp:price1>51,870000</hhp:price1>
    ...
    <hhp:price48>49,910000</hhp:price48>
  </hhp:HourlyHistoricalPrice>
  <hhp:HourlyHistoricalPrice xmlns:hhp="urn:or-HourlyHistoricalPrice">
    <hhp:indexId>1025127</hhp:indexId>
    <hhp:resetDate>20163112T000000</hhp:resetDate>
    <hhp:refSource>APX</hhp:refSource>
    <hhp:indexLocation/>
    <hhp:price1>63,870000</hhp:price1>
    ...
    <hhp:price48>29,910000</hhp:price48>
  </hhp:HourlyHistoricalPrice>  
</hhp:HourlyHistoricalPrices>

我只想检索具有 hhp:refSource 特定值的 hhp:HourlyHistoricalPrice 节点，例如AIBO。

我尝试了下面的 XPathExpression，但这什么也没检索到。

 XPathFactory xpf = XPathFactory.newInstance();
XPath xpath = xpf.newXPath();
        
String strExprssion = 
  "/hhp:HourlyHistoricalPrices/hhp:HourlyHistoricalPrice[hhp:refSource='AIBO']";
        
XPathExpression expression = xpath.compile(strExprssion);
        
NodeList nodes = (NodeList) expression.evaluate(originalXmlDoc, XPathConstants.NODESET);
        
System.out.println(nodes.getLength());

如果有人能够提供有关正确使用表达方式的建议，我将不胜感激。

非常感谢。

Answer 1

您需要将前缀扩展到它所代表的 xml 命名空间中:

String strExprssion = "//urn:or-HourlyHistoricalPrice:HourlyHistoricalPrice[urn:or-HourlyHistoricalPrice:refSource='AIBO']";

所以对我来说，这个测试类

public class XPathCheck {
    public static void main(String[] args) throws FileNotFoundException, IOException, XPathExpressionException {
        XPathFactory xpf = XPathFactory.newInstance();
        XPath xpath = xpf.newXPath();

        try (InputStream file = new FileInputStream(Paths.get("src", "inputFile.xml").toFile())) {
            String strExprssion = "//urn:or-HourlyHistoricalPrice:HourlyHistoricalPrice[urn:or-HourlyHistoricalPrice:refSource='AIBO']";
            XPathExpression expression = xpath.compile(strExprssion);
            NodeList nodes = (NodeList) expression.evaluate(new InputSource(file), XPathConstants.NODESET);

            System.out.println(nodes.getLength());
        }
    }
}

输出“2”。