正确的XPathExpression以检索Java中的节点吗？

Question

I have an XML document that has multiple hpp:HourlyHistoricalPrice elements as in the following way:

 <?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> 

I want to retrieve only the hhp:HourlyHistoricalPrice nodes that have a particular value for hhp:refSource , eg AIBO .

I was trying the below XPathExpression but this retrieves nothing.

  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()); 

I would be grateful if somebody could provide advise on the correct expression to use.

Thanks a lot.

Answer 1

You need to expand the prefix into the xml namespace it represents:

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

So for me, this test class

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());
        }
    }
}

outputs "2".