XPath String functions example

In the previous examples, we talked about how we can query for a particular node(s) and extract the attribute value from a node in an XML Document.

In this example, we shall see what other String operations on XPath are supported by the Java programming language.

The String operations are a range of functions that may be used to search/query. These functions operate on string variables or return a string in specific format.

Supported String functions:

Java supports the following String functions on XPath:

• text
• concat
• starts-with
• contains
• substring-before
• substring-after
• substring
• string-length
• normalize-space
• translate

Apart from these, there are several over-loaded versions of the methods mentioned above. We shall discuss all those methods in detail.

We will use the following XML file for our further examples.

cricketTeam_info.xml:

<?xml version="1.0" encoding="UTF-8"?>

<cricketers>
	<cricketer type="righty">
		<name>MS Dhoni</name>
		<role>Captain</role>
		<position>Wicket-Keeper</position>
	</cricketer>
	<cricketer type="lefty">
		<name>Shikhar Dhawan</name>
		<role>              Batsman</role>
		<position>Point</position>
	</cricketer>
	<cricketer type="righty">
		<name>Virat Kohli</name>
		<role>Batsman</role>
		<position>cover</position>
	</cricketer>
	<cricketer type="righty">
		<name>Shami</name>
		<role>Bowler</role>
		<position>SquareLeg</position>
	</cricketer>
	<cricketer type="lefty">
		<name>Zaheer Khan</name>
		<role>Bowler</role>
		<position>FineLeg</position>
	</cricketer>
</cricketers>

Examples:

1. text()

The text() method is used for the string representation of the node currently selected.

XPathExpression expr = xpath.compile("//cricketer[@type='righty']/name/text()");
String cricketer = (String) expr.evaluate(doc, XPathConstants.STRING);
System.out.println("The righty cricketer is : " + cricketer);

Output:

The righty cricketer is : Shikhar Dhawan

2. concat(String arg1,String arg2,String… arg3)

The concat(String arg1,String arg2,String... arg3) method is used to concat strings from the evaluation of two or more XPath expressions.

XPathExpression expr = xpath.compile("concat(//cricketer[name='Shami']/@type,//cricketer[name='Zaheer Khan']/@type)");
String combination = (String) expr.evaluate(doc, XPathConstants.STRING);
System.out.println("The concat result is : " + combination);

Output:

The concat result is : rightylefty

The arguments for concat method can also be static string objects.

XPathExpression expr = xpath.compile("concat(//cricketer[name='Shami']/@type,' Bowler'");

Output:

The concat result is : righty Bowler

3. contains(String target, String tosearch)

This method is used to search for a particular string in a target string. If the need is to find nodes with a particular String pattern, we use contains method. Look at the below code snippet how it is used.

XPathExpression expr = xpath.compile("//cricketer[contains(name,'MS')]/name/text()");
String msdesc = (String) expr.evaluate(doc, XPathConstants.STRING);
System.out.println("The Player with name containing 'MS' is : " + msdesc);

Output:

The Player with name containing 'MS' is : MS Dhoni

4. starts-with(string1, string2):

As the name indicates, the starts-with method determines if the a particular tag in the node starts with a particular string. Look at the example below to see how it is used:

XPathExpression expr = xpath.compile("//cricketer[starts-with(name,'Za')]/name/text()");
String startswith = (String) expr.evaluate(doc, XPathConstants.STRING);
System.out.println("The Player name starting-with 'Za'  is : " + startswith);

Output:

The Player name starting-with 'Za'  is : Zaheer Khan

5. substring-before(String target, String tosearch)

The substring-before is used to extract the part of string from the beginning of the string to the position where the second string in the argument starts. The example below demonstrates this clearly:

XPathExpression expr = xpath.compile("substring-before(//cricketer[name='MS Dhoni']/position,'-Keeper')");
String substrbefore = (String) expr.evaluate(doc, XPathConstants.STRING);
System.out.println("The substring before Keeper is : " + substrbefore);

Output:

The substring before Keeper is : Wicket

6. substring-after(String target, String tosearch)

The substring-before is used to extract the part of string from the first occurrence of the second string argument to the end of the string. The example below demonstrates this clearly:

XPathExpression expr = xpath.compile("substring-after(//cricketer[name='MS Dhoni']/position,'Wicket-')");
String substrafter = (String) expr.evaluate(doc, XPathConstants.STRING);
System.out.println("The substring after Keeper is : " + substrafter);

Output:

The substring before Keeper is : Keeper

7. substring(String target, int startingindex, int length)

The XPath offers a number of overloaded substring functions to work. The substring(String target, int startingindex, int length) method is used to extract a sub-string of specified length from the index position specified. There are other substring functions that maybe used as per the requirement. Lets look at an example of the substring :

XPathExpression expr = xpath.compile("substring(//cricketer[name='MS Dhoni']/position,'1','4')");
String substr = (String) expr.evaluate(doc, XPathConstants.STRING);
System.out.println("The substring is : " + substr);

Output:

The substring is : Wick

8. string-length(string)

This method is used to calculate the size of the string. Another overloaded version is the string-length(). This method is used to get the size of the currently selected node.

XPathExpression expr = xpath.compile("string-length(//cricketer[name='MS Dhoni']/position)");
String strlength = (String) expr.evaluate(doc, XPathConstants.STRING);
System.out.println("The length of the string is : " + strlength);

Output:

The length of the string is : 13

9. normalize-space(string)

This method is used to remove the leading and trailing spaces of the string. Another overloaded version is the normalize-space(). This one is used to remove the leading and trailing spaces of the currently selected node.

XPathExpression expr = xpath.compile("normalize-space(//cricketer[name='Shikhar Dhawan']/role/text())");
String result = (String) expr.evaluate(doc, XPathConstants.STRING);
System.out.println("The normalized string is : " + result);

Output:

The normalized string is : Batsman

10. translate(String targetString, String stringtoreplace, String replacementstring)

The translate method is used to replace the occurrences of a particular string with another string. An example will show how:

XPathExpressionexpr = xpath.compile("translate('Shikhar Dhawan','S','K')");
String replacedstring = (String) expr.evaluate(doc, XPathConstants.STRING);
System.out.println("The translated string is : " + replacedstring);

Output:

The translated string is : Khikhar Dhawan

XPathStringFunctionsDemo.java:

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Document;


public class XpathDemo
{
		public static void main(String[] args) throws Exception
		{

				DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
				documentBuilderFactory.setNamespaceAware(true);
				DocumentBuilder documentBuilder = documentBuilderFactory.newDocumentBuilder();
				Document doc = documentBuilder.parse("src/cricketTeam_info.xml");

				XPathFactory xpathFactory = XPathFactory.newInstance();
				XPath xpath = xpathFactory.newXPath();

				// XPath concat example
				XPathExpression expr = xpath.compile("concat(//cricketer[name='Shami']/@type,//cricketer[name='Zaheer Khan']/@type)");
				String combination = (String) expr.evaluate(doc, XPathConstants.STRING);
				System.out.println("The concat result is : " + combination);

				// XPath starts-with example
				expr = xpath.compile("//cricketer[starts-with(name,'Za')]/name/text()");
				String startswith = (String) expr.evaluate(doc, XPathConstants.STRING);
				System.out.println("The Player name starting-with 'Za'  is : " + startswith);

				// XPath contains example
				expr = xpath.compile("//cricketer[contains(name,'MS')]/name/text()");
				String msdesc = (String) expr.evaluate(doc, XPathConstants.STRING);
				System.out.println("The Player with name containing 'MS' is : " + msdesc);

				// XPath substring-before example
				expr = xpath.compile("substring-before(//cricketer[name='MS Dhoni']/position,'-Keeper')");
				String substrbefore = (String) expr.evaluate(doc, XPathConstants.STRING);
				System.out.println("The substring before Keeper is : " + substrbefore);

		   	// XPath substring-after example
				expr = xpath.compile("substring-after(//cricketer[name='MS Dhoni']/position,'Wicket-')");
				String substrafter = (String) expr.evaluate(doc, XPathConstants.STRING);
				System.out.println("The substring after Keeper is : " + substrafter);

				// XPath substring example
				expr = xpath.compile("substring(//cricketer[name='MS Dhoni']/position,'1','4')");
				String substr = (String) expr.evaluate(doc, XPathConstants.STRING);
				System.out.println("The substring is : " + substr);

				// XPath string-length(string) example
				expr = xpath.compile("string-length(//cricketer[name='MS Dhoni']/position)");
				String strlength = (String) expr.evaluate(doc, XPathConstants.STRING);
				System.out.println("The length of the string is : " + strlength);

				// XPath normalize-space(string) example
				expr = xpath.compile("normalize-space(//cricketer[name='Shikhar Dhawan']/role/text())");
				String result = (String) expr.evaluate(doc, XPathConstants.STRING);
				System.out.println("The normalized string is : " + result);

				expr = xpath.compile("translate('Shikhar Dhawan','S','K')");
				String replacedstring = (String) expr.evaluate(doc, XPathConstants.STRING);
				System.out.println("The translated string is : " + replacedstring);
		}
}

Conclusion

Here we looked at the XPath String functions supported by Java.

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