从XPath获取值

Question

I need to get some values from this xml document:

<node id="A." label="General Literature">
        <isComposedBy>
            <node id="A.0" label="GENERAL">
                <isComposedBy>
                    <node label="Biographies/autobiographies"/>
                    <node label="Conference proceedings"/>
                    <node label="General literary works (e.g., fiction, plays)"/>
                </isComposedBy>
            </node>
            <node id="A.1" label="INTRODUCTORY AND SURVEY"/>
            <node id="A.2" label="REFERENCE (e.g., dictionaries, encyclopedias, glossaries)"/>
            <node id="A.m" label="MISCELLANEOUS"/>
        </isComposedBy>
    </node>

In Java how can i select only the nodes with the attributes id and label and then get the values of those attributes? I've tried with XPath using this expression:

XPathExpression expr = path.compile("//*/@id | /@label");

But this is not returning what i want.

Answer 1

Use XPathExpression expr = path.compile("//*[@id and @label]/(@id | /@label)"); with XPath 2.0 or XPathExpression expr = path.compile("//*[@id and @label]/@id | //*[@id and @label]/@label"); with XPath 1.0.

Answer 2

Using //node[@id and @label] will get all node elements having id and label attributes. Then you would need to loop over the nodes to get their attribute values. An example using DOM:

    for(int i = 0; i < nodes.getLength(); i++) {
        Node node = nodes.item(i);
        NamedNodeMap attributes = node.getAttributes();
        System.out.println(attributes.getNamedItem("id").getTextContent());
        System.out.println(attributes.getNamedItem("label").getTextContent());
    }

Answer 3

尝试这种方式：

XPathExpression expr = path.compile("//*/*[@id and @label]");