在Java中使用Xpath定位具有特定namepace的元素

Question

I'm trying to list elements with specific namespace using Xpath in Java. I have the following xml file:

<pd:ProcessDefinition xmlns:xsl="http://www.w3.org/1999/XSL/Transform"  xmlns:pd="http://newsample/cred/process/2007"  xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<pd:name>Processes/Schemas/GetInline.process</pd:name>
<pd:startName>StartThis</pd:startName>
<pd:startType>
    <xsd:element name="root">
        <xsd:complexType>
            <xsd:sequence>
                <xsd:element name="param" type="xsd:string"/>
            </xsd:sequence>
        </xsd:complexType>
    </xsd:element>
</pd:startType>
<pd:endName>End</pd:endName>
<pd:endType>
    <xsd:element name="End" type="xsd:string"/>
</pd:endType>
<pd:activity name="MapAnyelement">
    <config>
        <element>
            <xsd:choice>
                <xsd:element name="param" type="xsd:string"/>
                <xsd:element ref="pfx:param1"/>
            </xsd:choice>
        </element>
    </config>
    <pd:coercions>
        <pd:coercion xpath="root" element="pfx:param1"/>
    </pd:coercions>
    <pd:inputBindings/>
</pd:activity>
<pd:activity name="MapComplex">
    <config>
        <element>
            <xsd:element name="mapComplex">
                <xsd:complexType>
                    <xsd:sequence>
                        <xsd:element name="complex1" type="xsd:string"/>
                    </xsd:sequence>
                </xsd:complexType>
            </xsd:element>
        </element>
    </config>
    <pd:inputBindings>
        <mapComplex>
            <complex1>
                <xsl:value-of select="1"/>
            </complex1>
        </mapComplex>
    </pd:inputBindings>
</pd:activity>
<pd:activity name="MapElement">
    <config>
        <element>
            <xsd:element name="mapElement" type="xsd:string"/>
        </element>
    </config>
    <pd:inputBindings>
        <mapElement>
            <xsl:value-of select="1"/>
        </mapElement>
    </pd:inputBindings>
</pd:activity>
</pd:ProcessDefinition>

I'm using the following code to find if any of the complex elements in the file have descendents which have namespace prefix xs ie they belong to namespace http://www.w3.org/2001/XMLSchema .

String expression = "/ProcessDefinition/activity|//group/activity|/ProcessDefinition/starter";
NodeList nodeList = (NodeList) xPath.compile(expression).evaluate(
            dDoc, XPathConstants.NODESET);
NodeListIterator iter = new NodeListIterator(nodeList);
while(iter.hasNext()) {
    Node nNode = iter.next();
    Element elem = (Element) nNode;
    String aName = elem.getAttribute("name");
    String ns = "http://www.w3.org/2001/XMLSchema";
    String schemaExpr = "//*[namespace-uri() = '"+ns+"']";
    NodeList nN = (NodeList) xPath.compile(schemaExpr).evaluate(nNode, XPathConstants.NODESET);
    System.out.println("##### NodeList: " + nN.getLength());
}

However the code always returns NodeList nN size as '0'. What am I missing here?

Answer 1

In XPath, an unqualified name matches elements in no namespace. So /ProcessDefinition won't match <pd:ProcessDefinition> in your source document.

The simplest workaround is to use an XSLT 2.0+ processor (eg Saxon) and then either (1) set defaultXPathNamespace in the static context or (2) use steps of the form /*:ProcessDefinition/*:activity .

If you want to stick with XPath 1.0 you can write expressions of the form /pd:ProcessDefinition/pd:activity and set a namespace context that recognises the prefix "pd"; or you can write expressions in the form /*[local-name()='ProcessDefinition']/*[local-name()='activity']/...