Sample example to work with XPath
In the previous post we learned about the XPath where I mentioned about XPath nodes, XPath Constant, XPath datatypes, XPath syntax, predicates & wildcard in XPath. Now we will see, how to use XPath expressions to extract specific data from XML source document.
XPath Operators List:-
Operator | Description | Example |
| | Help to compute two nodes | //name|//java-experience |
or | or | salary=50000 or salary=45000 |
and | and | Salary>40000 and salary<60000 |
mod | Division reminder(modules) | 9 mod 2(Reminder 1) |
+ | Addition | 10 + 5 |
- | Subtraction | 10 – 5 |
* | Multiplication | 10 * 5 |
div | Division | 10 div 5 |
= | Equal | Salary = 50000 |
!= | Not equal | Salary != 50000 |
< | Less than | Salary < 50000 |
<= | Less than or equal to | Salary <= 50000 |
> | Greater than | Salary > 50000 |
>= | Greater than or equal to | Salary >= 50000 |
Many inbuilt functions are available in XPath, like Accessor, String, Numeric e.t.c. For more info visit
http://www.w3schools.com/xpath/xpath_functions.asp#string
A sample XML
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE note SYSTEM "employee.dtd">
<employees>
<!--Test is a comment-->
<employee id="1234">
<name>KUMAR GAURAV</name>
<designation>SYSTEM ENGINEER</designation>
<java-experience>7</java-experience>
<salary>50000</salary>
</employee>
<employee id="2341">
<name>KUMAR AADITYA</name>
<designation>PROGRAM MANAGER</designation>
<java-experience>15</java-experience>
<salary>70000</salary>
</employee>
</employees>
XPathSample.java
package com.gaurav.xpath.demo;
import java.io.IOException;
importjavax.xml.parsers.DocumentBuilder;
importjavax.xml.parsers.DocumentBuilderFactory;
importjavax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
importjavax.xml.xpath.XPathConstants;
importjavax.xml.xpath.XPathException;
importjavax.xml.xpath.XPathExpression;
importjavax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
/**
* @authorgaurav
*
*/
public class XPathSample {
/**
* This method will help to display the XML elements when we are using NODESET constant of XPath.
*
*/
publicstatic void displayXpathResult(Object result) {
NodeList nodes = (NodeList) result;
for(int i = 0; i < nodes.getLength(); i++) {
System.out.println(nodes.item(i).getNodeValue());
}
}
/**
* This method will help to display the XML elements when we are using NODESET constant of XPath and XPath wildcard.
*
*/
publicstatic void displayXpathWildCardResult(Object result) {
NodeList nodeList = (NodeList) result;
for(int i = 0; i < nodeList.getLength(); i++) {
if(nodeList.item(i).getFirstChild() != null) {
System.out.println(nodeList.item(i).getNodeName() + " : \t"
+ nodeList.item(i).getFirstChild().getNodeValue());
}
}
}
/**
* This method will help to display the XML elements when we are using NODE constant of XPath.
*
*/
privatestatic void displayXPathResultForNode(Node node) {
NodeList nodeListData;
if(null!= node) {
nodeListData = node.getChildNodes();
for (int i = 0;null!=nodeListData && i < nodeListData.getLength(); i++) {
Node nod = nodeListData.item(i);
if(nod.getNodeType() == Node.ELEMENT_NODE)
System.out.println(nodeListData.item(i).getNodeName() + " : " + nod.getFirstChild().getNodeValue());
}
}
}
publicstatic void main(String[] args) throws XPathException,
ParserConfigurationException, SAXException, IOException {
// DocumentBuilderFactory is created for reading xml file
DocumentBuilderFactory builderFactory = DocumentBuilderFactory
.newInstance();
// We can use this below line if we want to skip dtd available in the XML file
builderFactory
.setFeature(
"http://apache.org/xml/features/nonvalidating/load-external-dtd",
false);
DocumentBuilder builder = builderFactory.newDocumentBuilder();
Document document = builder.parse("src\\employees.xml");
// Creation of XPathFactory which is required for creating XPath Object
XPathFactory xPathFactory = XPathFactory.newInstance();
// Creation of XPath object from XPathFactory
XPath xpath = xPathFactory.newXPath();
// Compiling the XPath expression for getting all employee names
XPathExpression xPathExpr = xpath
.compile("/employees/employee/name/text()");
// XPath example using NODESET CONSTANT.
Object result = xPathExpr.evaluate(document, XPathConstants.NODESET);
System.out
.println("***** All available employees are as follows : *****");
displayXpathResult(result);
// XPath example using NODE CONSTANT.
System.out.println("\n***** All available employees are as follows using NODE CONSTANT : *****");
Node node = (Node) xpath.compile("/employees/employee[@id='2341']").evaluate(document, XPathConstants.NODE);
displayXPathResultForNode(node);
// get all employees salary using xpath expression in java
NodeList nodeList = (NodeList) xpath.compile(
"/employees/employee/salary/text()").evaluate(document,
XPathConstants.NODESET);
System.out
.println("\n***** All salaries for the available employees using NODESET CONSTANT : *****");
for(int i = 0; i < nodeList.getLength(); i++) {
System.out.println(nodeList.item(i).getNodeName() + "\t"
+ nodeList.item(i).getNodeValue());
}
// get only one(first) employee name using xpath expression in java
String nodeList1 = (String) xpath.compile(
"/employees/employee/name/text()").evaluate(document,
XPathConstants.STRING);
System.out
.println("\n***** Name of the first employee using STRING CONSTANT : *****");
System.out.println(nodeList1);
// XPath expression to use wildcard.
Object wildCardResult = xpath.compile("/employees/employee/*")
.evaluate(document, XPathConstants.NODESET);
System.out
.println("\n***** Displaying all element using wildcard in XPath expression : *****");
displayXpathWildCardResult(wildCardResult);
// XPath expression to count employee nodes in the XML source document.
Double count = (Double) xpath.compile("count(/employees/employee)")
.evaluate(document, XPathConstants.NUMBER);
System.out
.println("\n***** Use of Count with the help of NUMBER CONSTANT : *****");
System.out.println("How many employees are available : " + count);
// XPath conditional example
Boolean flag = (Boolean) xpath.compile(
"count(/employees/employee[@id='2341']) > 0").evaluate(
document, XPathConstants.BOOLEAN);
System.out
.println("\n***** Use of Count with the help of BOOLEAN CONSTANT : *****");
System.out
.println("Is any employee is available with the ID=1234 using BOOLEAN CONSTANT : "
+ flag);
}
}
Result:-
***** All available employees are as follows : *****
KUMAR GAURAV
KUMAR AADITYA
***** All available employees are as follows using NODE CONSTANT : *****
name : KUMAR AADITYA
designation : PROGRAM MANAGER
java-experience : 15
salary : 70000
***** All salaries for the available employees using NODESET CONSTANT : *****
#text 50000
#text 70000
***** Name of the first employee using STRING CONSTANT : *****
KUMAR GAURAV
***** Displaying all element using wildcard in XPath expression : *****
name : KUMAR GAURAV
designation : SYSTEM ENGINEER
java-experience : 7
salary : 50000
name : KUMAR AADITYA
designation : PROGRAM MANAGER
java-experience : 15
salary : 70000
***** Use of Count with the help of NUMBER CONSTANT : *****
How many employees are available : 2.0
***** Use of Count with the help of BOOLEAN CONSTANT : *****
Is any employee is available with the ID=1234 using BOOLEAN CONSTANT : true
