Use of "parent" in XPath expression
In our previous section of tutorials you have studied
how to use child axis in XPath expression . Now this section will describe
the use of "parent" axis. "parent" axis consists of
parent of the context node. In this example we have created an XML file "persons.xml"
as in our previous section, which is necessary to execute XPath query on
to it. This "persons.xml" contains information related to name,
age, gender of different persons. Our XML file persons.xml is as same as
in our previous examples.
Here is the full source code for persons.xml file
as follows :
persons.xml
<?xml version="1.0" ?>
<information>
<person id="1">
<name>Deep</name>
<age>34</age>
<gender>Male</gender>
</person>
<person id="2">
<name>Kumar</name>
<age>24</age>
<gender>Male</gender>
</person>
<person id="3">
<name>Deepali</name>
<age>19</age>
<gender>Female</gender>
</person>
<!-- more persons... -->
</information> |
Now we have declared a class XPathParentAxis and
in this class we are parsing the XML file with JAXP. First of all we need
to load the document into DOM Document object. We have put that
persons.xml file in that current working directory. DocumentBiuldFactory's
static method newInstance() is used to create a new instance of
DocumentBuilderFactory. Instance of DocumentBuilderFactory is used to create an
object of DocumentBuilder.
DocumentBuilderFactory domFactory =
DocumentBuilderFactory.newInstance();
domFactory.setNamespaceAware(true);
DocumentBuilder builder = domFactory.newDocumentBuilder();
Document doc = builder.parse("persons.xml"); |
Above lines of code parses "persons.xml"
file and creates a Document object. Next we have created XPath object
with the use of XPathFactory.
XPath xpath = XPathFactory.newInstance().newXPath(); |
In our example XPath expression
"//parent::*" will select all elements which are parent of context
node.
Here is the full example code of XPathParentAxis.java as
follows:
XPathParentAxis.java
import org.w3c.dom.*;
import javax.xml.xpath.*;
import javax.xml.parsers.*;
import java.io.IOException;
import org.xml.sax.SAXException;
public class XPathParentAxis {
public static void main(String[] args)
throws ParserConfigurationException, SAXException,
IOException, XPathExpressionException {
DocumentBuilderFactory domFactory =
DocumentBuilderFactory.newInstance();
domFactory.setNamespaceAware(true);
DocumentBuilder builder = domFactory.newDocumentBuilder();
Document doc = builder.parse("persons.xml");
XPath xpath = XPathFactory.newInstance().newXPath();
XPathExpression expr = xpath.compile("//parent::*");
// Selecting all element's Parent Axis
Object result = expr.evaluate(doc, XPathConstants.NODESET);
NodeList nodes = (NodeList) result;
for (int i = 0; i < nodes.getLength(); i++) {
System.out.println(nodes.item(i).getNodeName());
}
expr = xpath.compile("//parent::name/text()");
// Selecting all name element's Parent Axis
result = expr.evaluate(doc, XPathConstants.NODESET);
nodes = (NodeList) result;
for (int i = 0; i < nodes.getLength(); i++) {
System.out.print(nodes.item(i).getNodeValue()+", ");
}
expr = xpath.compile("//parent::age/text()");
// Selecting all age element's Parent Axis
result = expr.evaluate(doc, XPathConstants.NODESET);
nodes = (NodeList) result;
for (int i = 0; i < nodes.getLength(); i++) {
System.out.print(nodes.item(i).getNodeValue()+", ");
}
expr = xpath.compile("//parent::gender/text()");
//Selecting all gender elemenet's Parent Axis
result = expr.evaluate(doc, XPathConstants.NODESET);
nodes = (NodeList) result;
for (int i = 0; i < nodes.getLength(); i++) {
System.out.print(nodes.item(i).getNodeValue()+", ");
}
}
}
|
Output:
To run this example follow these stated steps:
- create persons.xml file
- create and save XPathParentAxis.java
- compile and execute XPathParentAxis class
file and you will get following console output.
Download Source Code