Read XML with JDOM2 Parser in Java

JDOM2 parser can be used to read XML, parse XML and write XML files after updating the content of it. It stores the JDOM2 documents in memory to read and modify their values. After loading the XML document into memory, JDOM2 maintains a strict parent-child type relationship. Parent-type JDOM instances (parent) have methods to access their content, and child-type JDOM instances (content) have methods to access their parent.

Please note that we have used lambda expressions and method references in this tutorial, so we must configure to project to use minimum Java version 1.8.

1. Maven

Include the latest version of jdom2 in the project.

<dependency>
  <groupId>org.jdom</groupId>
  <artifactId>jdom2</artifactId>
  <version>2.0.6.1</version>
</dependency>

To execute XPaths, we will need jaxen as well.

<dependency>
  <groupId>jaxen</groupId>
  <artifactId>jaxen</artifactId>
  <version>2.0.0</version>
</dependency>

2. Create JDOM2 Document

We can create org.jdom2.Document instance using any parser listed down below. They all parse the XML and return in-memory JDOM2 document.

2.1. Using DOM Parser

private static Document getDOMParsedDocument(final String fileName) {
  Document document = null;
  try {

    DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
    //If want to make namespace aware.
    //factory.setNamespaceAware(true);
    DocumentBuilder documentBuilder = factory.newDocumentBuilder();
    org.w3c.dom.Document w3cDocument = documentBuilder.parse(fileName);
    document = new DOMBuilder().build(w3cDocument);
  } 
  catch (IOException | SAXException | ParserConfigurationException e) {
    e.printStackTrace();
  }
  return document;
}

2.2. Using SAX Parser

private static Document getSAXParsedDocument(final String fileName) {

  SAXBuilder builder = new SAXBuilder(); 
  Document document = null;
  try {

    document = builder.build(fileName);
  } 
  catch (JDOMException | IOException e) {
    e.printStackTrace();
  }
  return document;
}

2.3. Using StAX Parser

private static Document getStAXParsedDocument(final String fileName) {
   
  Document document = null;
  try {

    XMLInputFactory factory = XMLInputFactory.newFactory();
    XMLEventReader reader = factory.createXMLEventReader(new FileReader(fileName));
    StAXEventBuilder builder = new StAXEventBuilder(); 
    document = builder.build(reader);
  } 
  catch (JDOMException | IOException | XMLStreamException e) {
    e.printStackTrace();
  }
  return document;
}

3. Reading XML Content

We will be reading the following employees.xml file.

<employees>
  <employee id="101">
    <firstName>Lokesh</firstName>
    <lastName>Gupta</lastName>
    <country>India</country>
    <department id="25">
      <name>ITS</name>
    </department>
  </employee>
  <employee id="102">
    <firstName>Brian</firstName>
    <lastName>Schultz</lastName>
    <country>USA</country>
    <department id="26">
      <name>DEV</name>
    </department>
  </employee>
</employees>

3.1. Root Node

Use document.getRootElement() method.

String xmlFile = "employees.xml";
Document document = getSAXParsedDocument(xmlFile);

Element rootNode = document.getRootElement();
System.out.println("Root Element :: " + rootNode.getName());

Program output:

Root Element :: employees

3.2. Attribute Value

Use Element.getAttributeValue() method.

public static void main(String[] args) {
	String xmlFile = "employees.xml";
	Document document = getSAXParsedDocument(xmlFile);

	Element rootNode = document.getRootElement();

	rootNode.getChildren("employee").forEach( ReadXMLDemo::readEmployeeNode );
}

private static void readEmployeeNode(Element employeeNode) {
	//Employee Id
	System.out.println("Id : " + employeeNode.getAttributeValue("id"));
}

Program output:

Id : 101
Id : 102

3.3. Element Value

Use Element.getChildText() or Element.getText() methods.

public static void main(String[] args) {

	String xmlFile = "employees.xml";
	Document document = getSAXParsedDocument(xmlFile);

	Element rootNode = document.getRootElement();

	rootNode.getChildren("employee").forEach( ReadXMLDemo::readEmployeeNode );
}

private static void readEmployeeNode(Element employeeNode) {

	//Employee Id
	System.out.println("Id : " + employeeNode.getAttributeValue("id"));

	//First Name
	System.out.println("FirstName : " + employeeNode.getChildText("firstName"));

	//Last Name
	System.out.println("LastName : " + employeeNode.getChildText("lastName"));

	//Country
	System.out.println("country : " + employeeNode.getChild("country").getText());

	/**Read Department Content*/
	employeeNode.getChildren("department").forEach( ReadXMLDemo::readDepartmentNode );
}

private static void readDepartmentNode(Element deptNode) {

	//Department Id
	System.out.println("Department Id : " + deptNode.getAttributeValue("id"));

	//Department Name
	System.out.println("Department Name : " + deptNode.getChildText("name"));
}

Program output:

FirstName : Lokesh
LastName : Gupta
country : India
Department Id : 25
Department Name : ITS

FirstName : Brian
LastName : Schultz
country : USA
Department Id : 26
Department Name : DEV

4. Using XPath

To read any set of element’s values using xpath, we need to compile XPathExpression and use it’s evaluate() method.

String xmlFile = "employees.xml";
Document document = getSAXParsedDocument(xmlFile);

XPathFactory xpfac = XPathFactory.instance();

//Read employee ids
XPathExpression<Attribute> xPathA = xpfac.compile("//employees/employee/@id", Filters.attribute());

for (Attribute att : xPathA.evaluate(document)) {
	System.out.println("Employee Ids :: " + att.getValue());
}

//Read employee first names
XPathExpression<Element> xPathN = xpfac.compile("//employees/employee/firstName", Filters.element());

for (Element element : xPathN.evaluate(document)) {
	System.out.println("Employee First Name :: " + element.getValue());
}

Program output:

Employee Ids :: 101
Employee Ids :: 102

Employee First Name :: Lokesh
Employee First Name :: Brian

5. Complete Example

Here is the complete code to read XML using JDOM2 in java.

import java.io.FileReader;
import java.io.IOException;
 
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamException;
 
import org.jdom2.Attribute;
import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.JDOMException;
import org.jdom2.filter.Filters;
import org.jdom2.input.DOMBuilder;
import org.jdom2.input.SAXBuilder;
import org.jdom2.input.StAXEventBuilder;
import org.jdom2.xpath.XPathExpression;
import org.jdom2.xpath.XPathFactory;
import org.xml.sax.SAXException;
 
@SuppressWarnings("unused")
public class ReadXMLDemo 
{ 
  public static void main(String[] args) 
  {
    String xmlFile = "employees.xml";
    Document document = getSAXParsedDocument(xmlFile);
     
    /**Read Document Content*/
     
    Element rootNode = document.getRootElement();
    System.out.println("Root Element :: " + rootNode.getName());
     
    System.out.println("\n=================================\n");
     
    /**Read Employee Content*/
     
    rootNode.getChildren("employee").forEach( ReadXMLDemo::readEmployeeNode );
     
    System.out.println("\n=================================\n");
     
    readByXPath(document);
  }
   
  private static void readEmployeeNode(Element employeeNode) 
  {
    //Employee Id
    System.out.println("Id : " + employeeNode.getAttributeValue("id"));
     
    //First Name
    System.out.println("FirstName : " + employeeNode.getChildText("firstName"));
     
    //Last Name
    System.out.println("LastName : " + employeeNode.getChildText("lastName"));
     
    //Country
    System.out.println("country : " + employeeNode.getChild("country").getText());
     
    /**Read Department Content*/
    employeeNode.getChildren("department").forEach( ReadXMLDemo::readDepartmentNode );
  }
   
  private static void readDepartmentNode(Element deptNode) 
  {
    //Department Id
    System.out.println("Department Id : " + deptNode.getAttributeValue("id"));
     
    //Department Name
    System.out.println("Department Name : " + deptNode.getChildText("name"));
  }
   
  private static void readByXPath(Document document) 
  {
    //Read employee ids
    XPathFactory xpfac = XPathFactory.instance();
    XPathExpression<Attribute> xPathA = xpfac.compile("//employees/employee/@id", Filters.attribute());
    for (Attribute att : xPathA.evaluate(document)) 
    {
      System.out.println("Employee Ids :: " + att.getValue());
    }
     
    XPathExpression<Element> xPathN = xpfac.compile("//employees/employee/firstName", Filters.element());
    for (Element element : xPathN.evaluate(document)) 
    {
      System.out.println("Employee First Name :: " + element.getValue());
    }
  }
   
  private static Document getSAXParsedDocument(final String fileName) 
  {
    SAXBuilder builder = new SAXBuilder(); 
    Document document = null;
    try
    {
      document = builder.build(fileName);
    } 
    catch (JDOMException | IOException e) 
    {
      e.printStackTrace();
    }
    return document;
  }
   
  private static Document getStAXParsedDocument(final String fileName) 
  {
     
    Document document = null;
    try
    {
      XMLInputFactory factory = XMLInputFactory.newFactory();
      XMLEventReader reader = factory.createXMLEventReader(new FileReader(fileName));
      StAXEventBuilder builder = new StAXEventBuilder(); 
      document = builder.build(reader);
    } 
    catch (JDOMException | IOException | XMLStreamException e) 
    {
      e.printStackTrace();
    }
    return document;
  }
   
  private static Document getDOMParsedDocument(final String fileName) 
  {
    Document document = null;
    try
    {
      DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
      //If want to make namespace aware.
          //factory.setNamespaceAware(true);
      DocumentBuilder documentBuilder = factory.newDocumentBuilder();
      org.w3c.dom.Document w3cDocument = documentBuilder.parse(fileName);
      document = new DOMBuilder().build(w3cDocument);
    } 
    catch (IOException | SAXException | ParserConfigurationException e) 
    {
      e.printStackTrace();
    }
    return document;
  }
   
  /*private static String readFileContent(String filePath) 
  {
      StringBuilder contentBuilder = new StringBuilder();
      try (Stream<String> stream = Files.lines( Paths.get(filePath), StandardCharsets.UTF_8)) 
      {
          stream.forEach(s -> contentBuilder.append(s).append("\n"));
      }
      catch (IOException e) 
      {
          e.printStackTrace();
      }
      return contentBuilder.toString();
  }*/
}

Program output:

Root Element :: employees

=================================

Id : 101
FirstName : Lokesh
LastName : Gupta
country : India
Department Id : 25
Department Name : ITS
Id : 102
FirstName : Brian
LastName : Schultz
country : USA
Department Id : 26
Department Name : DEV

=================================

Employee Ids :: 101
Employee Ids :: 102
Employee First Name :: Lokesh
Employee First Name :: Brian

Happy Learning !!

Sourcecode on Github