使用XPathFactory评估Xpath属性

Question

I'm trying to do something quite simple I think, simply assert that an attribute of an Xpath node is a specific value. The node has no value, onlya an attribute value as follows:- <ControlResponse Success="true"/> (will return "true" or "false")

<?xml version="1.0" encoding="UTF-8"?><tag0:AAA_ControlRS xmlns:tag0="http://www.xmltravel.com/fab/2002/09" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" Target="test"     Version="2002A" xsi:type="AAA_ControlRS">
<tag0:TestInfo TestId="THFTEST"/>
<tag0:SessionInfo CreateNewSession="true"/>
<AAASessionId="8IzujBAVOPVQrO1ySpNBoJ9x"/>
<tag0:ControlResponse Success="true"/>
</tag0:AAA_ControlRS>

and here is my code:

//REQUEST
    String controlRequest = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n...
//bunch of xml here";

   //RESPONSE
    String myControlResponse = given().
            when().
            request().
            contentType("text/xml").
            body(myControlRequest).
            when().post().andReturn().asString();

    //Parse response and get relevant node via Xpath
    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    factory.setNamespaceAware(true);
    DocumentBuilder builder;
    Document doc;

    try {
        builder = factory.newDocumentBuilder();
        doc = builder.parse(new InputSource((new StringReader(myControlResponse))));

        //Xpath Factory Object
        XPathFactory xPathFactory = XPathFactory.newInstance();

        //Xpath Object
        XPath xpath = xPathFactory.newXPath();

        String controlResponse = getNodeValue(doc, xpath);

        assertEquals("true", controlResponse);


    } catch (ParserConfigurationException | org.xml.sax.SAXException | IOException e) {
        e.printStackTrace();
    }
}

private static String getNodeValue(Document doc, XPath xpath) {
    String controlResponse = null;
    try {
        XPathExpression expr =
                xpath.compile("//ControlResponse/@Success");
        controlResponse = (String) expr.evaluate(doc, XPathConstants.STRING);
    } catch (XPathExpressionException e) {
        e.printStackTrace();
    }

    return controlResponse;
}

The xpath evaluates to null when I expect the String "true". I want to achieve getting the attribute value and asserting if it contains string "true" or "false"

Is there an easier way of achieving what I'm trying to do?

Answer 1

To get the attribute value , use //ControlResponse/@Success as the XPath expression.

If namespace issues get in your way, use //*[local-name()="ControlResponse"]/@Success for a quick check, if the problem is namespace related.

Example using an unrelated sample document:

> cat ~/test.xml
<root><foo bar="true"/></root>
> xmllint --xpath '//foo/@bar' ~/test.xml
 bar="true"

If this doesn't work as expected in your case, please show enough of the XML document that the problem is reproducible.