Java Read XML – Java DOM Parser Example

In this Java xml parser tutorial, Learn to read xml with DOM parser in Java. DOM parser is intended for working with XML as an object graph (a tree like structure) in memory – so called “Document Object Model (DOM)“.

In first, the parser traverses the input XML file and creates DOM objects corresponding to the nodes in XML file. These DOM objects are linked together in a tree like structure. Once the parser is done with parsing process, we get this tree-like DOM object structure back from it. Now we can traverse the DOM structure back and forth as we want – to get/update/delete data from it.

Table of Contents

1. DOM Parser API
   -Import XML-related packages
   -Create a DocumentBuilder
   -Create a Document from a file or stream
   -Validate Document structure
   -Extract the root element
   -Examine attributes
   -Examine sub-elements
2. Read XML with DOM parser
3. Read data to POJO objects
4. Parse "unknown" xml with DOM parser

Read More : Difference between DOM parser and SAX parser

For example purpose, We will be parsing below xml content in all code examples.

<employees>
    <employee id="111">
        <firstName>Lokesh</firstName>
        <lastName>Gupta</lastName>
        <location>India</location>
    </employee>
    <employee id="222">
        <firstName>Alex</firstName>
        <lastName>Gussin</lastName>
        <location>Russia</location>
    </employee>
    <employee id="333">
        <firstName>David</firstName>
        <lastName>Feezor</lastName>
        <location>USA</location>
    </employee>
</employees>

1. DOM Parser API

Let’s note down some broad steps to create and use DOM parser to parse a XML file in java.

DOM Parser in Action
DOM Parser in Action

1.1. Import dom parser packages

We will need to import dom parser packages first in our application.

import org.w3c.dom.*;
import javax.xml.parsers.*;
import java.io.*;

1.2. Create DocumentBuilder

Next step is to create the DocumentBuilder object.

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();

1.3. Create Document object from xml file

Read the XML file to Document object.

Document document = builder.parse(new File( file ));

1.4. Validate Document structure

XML validation is optional but good to have it before start parsing.

Schema schema = null;
try {
  String language = XMLConstants.W3C_XML_SCHEMA_NS_URI;
  SchemaFactory factory = SchemaFactory.newInstance(language);
  schema = factory.newSchema(new File(name));
} catch (Exception e) {
    e.printStackStrace();
}
Validator validator = schema.newValidator();
validator.validate(new DOMSource(document));

1.5. Extract the root element

We can get the root element from XML document using below code.

Element root = document.getDocumentElement();

1.6. Examine attributes

We can examine the xml element attributes using below methods.

element.getAttribute("attributeName") ;    //returns specific attribute
element.getAttributes();                //returns a Map (table) of names/values

1.7. Examine sub-elements

Child elements can inquired in below manner.

node.getElementsByTagName("subElementName") //returns a list of sub-elements of specified name
node.getChildNodes()                         //returns a list of all child nodes

2. Read XML with DOM parser

In below example code, I am assuming that user is already aware of the structure of employees.xml file (it’s nodes and attributes); So example directly start fetching information and start printing it in console. In real life application, we will use this information for some real purpose rather than printing it on console and leave.

//Get Document Builder
DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();

//Build Document
Document document = builder.parse(new File("employees.xml"));

//Normalize the XML Structure; It's just too important !!
document.getDocumentElement().normalize();

//Here comes the root node
Element root = document.getDocumentElement();
System.out.println(root.getNodeName());

//Get all employees
NodeList nList = document.getElementsByTagName("employee");
System.out.println("============================");

for (int temp = 0; temp < nList.getLength(); temp++)
{
 Node node = nList.item(temp);
 System.out.println("");    //Just a separator
 if (node.getNodeType() == Node.ELEMENT_NODE)
 {
    //Print each employee's detail
    Element eElement = (Element) node;
    System.out.println("Employee id : "    + eElement.getAttribute("id"));
    System.out.println("First Name : "  + eElement.getElementsByTagName("firstName").item(0).getTextContent());
    System.out.println("Last Name : "   + eElement.getElementsByTagName("lastName").item(0).getTextContent());
    System.out.println("Location : "    + eElement.getElementsByTagName("location").item(0).getTextContent());
 }
}

Program Output:

employees
============================

Employee id : 111
First Name : Lokesh
Last Name : Gupta
Location : India

Employee id : 222
First Name : Alex
Last Name : Gussin
Location : Russia

Employee id : 333
First Name : David
Last Name : Feezor
Location : USA

3. Read data to POJO objects

Another real life application’s requirement might be populating the DTO objects with information fetched in above example code. I wrote a simple program to help you understand how it can be done easily.

Let’s say we have to populate Employee objects which is defined as below.

public class Employee
{
   private Integer id;
   private String firstName;
   private String lastName;
   private String location;
   
   //Setters and Getters
   
   @Override
   public String toString()
   {
      return "Employee [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", location=" + location + "]";
   }
}

Now look at the example code to populate employee objects list. Its just as simple as inserting few lines in between the code, and then copy the values in DTOs instead of console.

Java program to read XML file with DOM parser.

public class PopulateDTOExamplesWithParsedXML
{
   public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException
   {
        List<Employee> employees = parseEmployeesXML();
        System.out.println(employees);
   }

   private static List<Employee> parseEmployeesXML() throws ParserConfigurationException, SAXException, IOException
   {
      //Initialize a list of employees
      List<Employee> employees = new ArrayList<Employee>();
      Employee employee = null;
      
      DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
      DocumentBuilder builder = factory.newDocumentBuilder();
      Document document = builder.parse(new File("employees.xml"));
      document.getDocumentElement().normalize();
      NodeList nList = document.getElementsByTagName("employee");
      for (int temp = 0; temp < nList.getLength(); temp++)
      {
         Node node = nList.item(temp);
         if (node.getNodeType() == Node.ELEMENT_NODE)
         {
            Element eElement = (Element) node;
            //Create new Employee Object
            employee = new Employee();
            employee.setId(Integer.parseInt(eElement.getAttribute("id")));
            employee.setFirstName(eElement.getElementsByTagName("firstName").item(0).getTextContent());
            employee.setLastName(eElement.getElementsByTagName("lastName").item(0).getTextContent());
            employee.setLocation(eElement.getElementsByTagName("location").item(0).getTextContent());
            
            //Add Employee to list
            employees.add(employee);
         }
      }
      return employees;
   }
}

Program Output.

[Employee [id=111, firstName=Lokesh, lastName=Gupta, location=India], 
Employee [id=222, firstName=Alex, lastName=Gussin, location=Russia], 
Employee [id=333, firstName=David, lastName=Feezor, location=USA]]

4. Parse “unknown” xml with DOM parser

Previous example shows the way we can iterate over an XML document parsed with known or little know structure to you, while you are writing the code. In some cases, we may have to write the code in such a way such that even if there is some differences in assumed XML structure while coding, program must work without failure.

Here we are iterating over all elements present in XML document tree. we can add our knowledge and modify the code such that as soon as we get required information while traversing the tree, we just use it.

public class ParseUnknownXMLStructure
{
   public static void main(String[] args) throws ParserConfigurationException, SAXException, IOException
   {
      //Get Document Builder
      DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
      DocumentBuilder builder = factory.newDocumentBuilder();
      
      //Build Document
      Document document = builder.parse(new File("employees.xml"));
      
      //Normalize the XML Structure; It's just too important !!
      document.getDocumentElement().normalize();
      
      //Here comes the root node
      Element root = document.getDocumentElement();
      System.out.println(root.getNodeName());
      
      //Get all employees
      NodeList nList = document.getElementsByTagName("employee");
      System.out.println("============================");
      
      visitChildNodes(nList);
   }

   //This function is called recursively
   private static void visitChildNodes(NodeList nList)
   {
      for (int temp = 0; temp < nList.getLength(); temp++)
      {
         Node node = nList.item(temp);
         if (node.getNodeType() == Node.ELEMENT_NODE)
         {
            System.out.println("Node Name = " + node.getNodeName() + "; Value = " + node.getTextContent());
            //Check all attributes
            if (node.hasAttributes()) {
               // get attributes names and values
               NamedNodeMap nodeMap = node.getAttributes();
               for (int i = 0; i < nodeMap.getLength(); i++)
               {
                   Node tempNode = nodeMap.item(i);
                   System.out.println("Attr name : " + tempNode.getNodeName()+ "; Value = " + tempNode.getNodeValue());
               }
               if (node.hasChildNodes()) {
                  //We got more childs; Let's visit them as well
                  visitChildNodes(node.getChildNodes());
               }
           }
         }
      }
   }
}

Program Output.

employees
============================
Node Name = employee; Value = 
        Lokesh
        Gupta
        India
    
Attr name : id; Value = 111
Node Name = firstName; Value = Lokesh
Node Name = lastName; Value = Gupta
Node Name = location; Value = India
Node Name = employee; Value = 
        Alex
        Gussin
        Russia
    
Attr name : id; Value = 222
Node Name = firstName; Value = Alex
Node Name = lastName; Value = Gussin
Node Name = location; Value = Russia
Node Name = employee; Value = 
        David
        Feezor
        USA
    
Attr name : id; Value = 333
Node Name = firstName; Value = David
Node Name = lastName; Value = Feezor
Node Name = location; Value = USA

That’s all for this good to know concept’s around Java XML DOM Parser. Drop me a comment if something is not clear OR needs more explanation.

Happy Learning !!

Reference:

http://www.w3c.org/DOM/

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26 thoughts on “Java Read XML – Java DOM Parser Example”

  1. I have a task to transform xml and xsl file to html. The problem is, the xml and xsl files are uploaded through file upload so i dont have the file object. I have xml and xsl code file contents.
    Please help me as to how to transform the contents only.

    Reply
  2. Hi
    I tried to run your code,
    while executing and examining node.hasChildNode() always return true and getChildNode().getLength() always return integer values even if there are no child node present.

    for ex . Node Lastname in your xml doesnt contain any child node but hasChildNode returns true for the same, it should return false in order for me to do some coding for my project need.

    im using the sample xml used here.

    Thanks,
    Rohini Rangaswany

    Reply
  3. My requirement is the Write a new corn job to export all users in an XML format. Use the
    DOM java class to export to xml. This job should run at 5 pm IST in Hybris

    Reply
  4. I want to parse html file.
    Tried by

    Document htmlFilePath = DocumentBuilderFactory.newInstance()
    .newDocumentBuilder().parse(htmlFilePath);
    

    but getting error.
    It needs xml file only.
    How I can parse html file?

    Reply
  5. hi,
    i dont know how i get data if the XML is little more complex and every employee look like that:

    David
    Feezor

    USA
    NY
    NY

    how can i get to the data in city ?

    thanks!

    Reply
  6. I have a XML file. I want to get a XML from the same XML as a subset. How to do it in java please give an code example.

    Its urgent please provide your input.

    Lots of thanks.

    Reply
  7. Hi Lokesh,

    I need to transform XHTML span tags with certain style to another (similar) XML structure.

    For example, this element should be converted:

    <span style="font-weight: bold;">Bold Text</span>
    [/xml
    To:
    [xml]
    <content styleCode="bold">Fett1<br/> </content>
    

    This simple example, I could implement by renaming nodes and attributes.

    But there are style attributes that I can’t match. In this case I need to ignore/remove the element node but keep its content:

    Eg. I can’t map span element when their style attribute is “text-decoration: underline;” :

    <span style="font-weight: bold;">Bold<br /> 
    	<span style="font-style: italic;">BoldItalic<br /> 
    		<span style="text-decoration: line-through;">
    			BoldItalicLineThrough
    		    <span style="text-decoration: underline;">BoldItalicLineThroughUnderline</span>
    		</span>
    	</span>
    	<br />
    	Bold2
    </span>
    

    The element “span style=”text-decoration: underline” should be ignored/removed but the content (child nodes) should remain (text and span elements that can be mapped).

    Do you know how this could be implemented? I appreciate any help.

    So the expected result should be:

    <content styleCode="bold">Bold<br/> 
    	<content styleCode="italics">BoldItalic<br/> 
    			BoldItalicLineThrough
    		    <content styleCode="underline">BoldItalicLineThroughUnderline</content>
    	</content>
    	<br/>
    	Bold2
    </content>
    

    Thanks Benjamin!

    Reply
  8. I am stuck up with this!!! I want to fetch the value of ns1:uri based on the choices for SMS, MMS…

    true

    tel:+46123456758
    E164

    mmsChannel
    MMS

    00

    true

    tel:+46123456758
    E164

    SMS Dummy
    SMS

    00

    true

    tel:+464611223344
    E164

    faxChannel
    FAX

    true

    tel:+46123456758
    E164

    CCS MWI
    MWI

    Could you please help me with some sort of hint to read this value. TIA

    Reply
  9. Hi Lokesh,
    If there is one more tag named department inside , then how can we do it in unknown xml structure. to get bith employee as well as department details

    Reply
  10. what if the nodes have furthur node like

    <launch>
            <announced>23 march 2011</announced>
            <status>available</status>
    </launch>
    

    now when i give launch in getElementByTagName then it prints the data as 23 march 2011available without any space among them … how to put the space between these node’s contents…

    Reply
  11. Following is the code used and below element contents are changed which is not desired by replacing the escape character,

    <SelectionFilter>event.ProductType == &quot;CM_Media_Server&quot; and event.ProductVer == &quot;3.0.0.6&quot; and event.ProductPatch == &quot;0&quot;</SelectionFilter>
     
    <SelectionFilter>event.ProductType == "CM_Media_Server" and          event.ProductVer == "3.0.0.6" and event.ProductPatch == "0"</SelectionFilter>
    

    Below is the code used,

    Document xmlDocument = DocumentBuilderFactory.newInstance()
    .newDocumentBuilder().parse(SourceXMLFile);
    XPath xPath = XPathFactory.newInstance().newXPath();
    XPathExpression exprPre = xPath
    .compile(“/SPIRITConfiguration/@Version”);
    NodeList list = (NodeList) exprPre.evaluate(xmlDocument,
    XPathConstants.NODESET);
    for (int i = 0; i < list.getLength(); i++) {
    list.item(i).setTextContent(ModelVersion.getValue());
    }

    // write the content back into new renamed xml file
    TransformerFactory transformerFactory = TransformerFactory
    .newInstance();
    Transformer transformer = transformerFactory.newTransformer();
    DOMSource source = new DOMSource(xmlDocument);
    StreamResult result = new StreamResult(new File(DestxmlFile));
    transformer.transform(source, result);
    Kindly help me on this. Thank you in advance.

    Reply
  12. Hello Sir,
    I got a requirement that I have to map my xml to java object without parsing it, but the problem is like that in xml tag names would be same, for example,

    Sharique
    24
    India</name

    and class would be like this
    public class Employee{
    private String empName;
    private int age;
    private String country;

    //getters and setters
    }

    Please help

    Reply
  13. Hi Lokesh,
    I’m struggling with a problem like I have xml which have repeated child node with same name so when I’m trying to fetch all child node values DOM parser returns only first child value.My xml looks like …

    Lokesh
    Gupta
    India
    A
    B
    C
    P
    K
    S

    How can I parse it using dom parser to get all repeated values?Please respond.

    Reply
  14. Thanks for the tutorial, it really helped me, but i was wondering…Is there a way to “format” the output?

    I mean, you get the info like this :

    Node Name = employee; Value =
    Lokesh
    Gupta
    India

    Attr name : id; Value = 111
    Node Name = firstName; Value = Lokesh
    Node Name = lastName; Value = Gupta
    Node Name = location; Value = India

    But is there a way to just print :

    Name : Lokesh
    Last Name : Gupta
    Location : India

    ###########

    // And so on for every other Employee

    Thank you!

    Reply
    • I seriously doubt that there is any API support. Reason is simple that you are expected to store the values in some java objects and not directly print them anywhere.
      Here after populating the java objects, you can override toString() method to print the content the way you like.

      Reply
    • In broader sense, yes, they are somehow same. But if you look closely, they are different things. Parsers are used to generate/populate java objects or simply analyzing the XML data. Java POJOs object’s are optional here.
      In JAXB, java POJOs are mandatory. JAXB acts as a bridge between XML and java POJOs. What’s parsers do is just a small portion of JAXB. JAXB is much more than that.

      Reply

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