How to delete node from XML file using DOM Parser in Java?

Problem Description:

Suppose we have following XML file as an example.

<Employees>

   <Employee id="1">
       <name>abc</name>
       <age>23</age>
   </Employee >
  <Employee id="2">
       <name>xyz</name>
       <age>29</age>
   </Employee>
   <Employee id="3">
       <name>lmn</name>
       <age>34</age>
   </Employee>

</Employees>

Here requirement is to delete child node Employee whose id is 2.  Similarly user can delete any child node.

Steps:

1) Parse XML file or Create an instance of Document interface present in org.w3c.dom.* package.

For Creating an instance of Document interface we need to use DocumentBuilderFactory, DocumentBuilder classes present in javax.xml.parsers.* package and File class present in java.io.* package.

File file = new File(XML_file_location);

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

DocumentBuilder builder = factory.newDocumentBuilder();

Document document = builder.parse(file);

2) Enter employee id that you want to delete.

Figure 1

3) Get all the child nodes Employee of root node Employees. It returns the instance of NodeList interface present in org.w3c.dom.* package.

NodeList list = document.getElementsByTagName("Employee");

4) Now one by one examine each child node Employee.

• From all the child nodes that we got in Step 3 take one child node. It returns instance of Node interface present in org.w3c.dom.* package.

          Node node = list.item(i);

• Check whether this node is Element node or not?

          if (node.getNodeType() == Node.ELEMENT_NODE) { }

• If it is an Element node then typecast it and get its data (attributes and properties).

          Element element = (Element) node;

• Get its id as follows.

          String id=element.getAttribute("id");

• Compare this id with id of Employee that you want to delete.

         if (String.valueOf(id).equals(element.getAttribute("id"))) {}

• If id found then get previous sibling of selected node as follows.

          Node prev = node.getPreviousSibling();

• If sibling is text node then delete it from root node Employees.

          if (prev != null && prev.getNodeType() == Node.TEXT_NODE && prev.getNodeValue().trim().length() == 0) {

document.getDocumentElement().removeChild(prev);

}

• Now delete selected Employee node from root node Employees.

          document.getDocumentElement().removeChild(element);

5) Create an instance of Transformer class present in javax.xml.transform.* package. 

For creating an instance of Transformer class we need to use TransformerFactory class present in javax.xml.transform.* package.

TransformerFactory tFactory = TransformerFactory.newInstance();
Transformer transformer = tFactory.newTransformer();

6) Set xml file indentation (Optional)

transformer.setOutputProperty(OutputKeys.INDENT, "yes");

7) Create an instance of DOMSource class present in javax.xml.transform.dom.* package and pass instance of Document interface created in step 1.

DOMSource source = new DOMSource(document);

8) Create an instance of StreamResult class present in javax.xml.transform.stream.* package.

For creating an instance of StreamResult class first we need to create an instance of File class present in java.io.* package.

File file = new File(location_of_xml_file);
StreamResult result = new StreamResult(file);

9) Transform XML Source to a Result.

transformer.transform(source, result);

Software Required:

1. JDK
2. Eclipse
3. Maven

Note : I suggest to use latest version of all the software. If you need any help regarding these software installation please comment below I will help you.

Project Structure:

Figure 2

Java Code:

employee.xml

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<Employees>
<Employee id="1">
<name>Rohit</name>
<gender>male</gender>
<age>25</age>
<role>Programmer</role>
</Employee>
<Employee id="2">
<name>Bhavna</name>
<gender>female</gender>
<age>20</age>
<role>Student</role>
</Employee>
</Employees>

pom.xml


Employee.java


DeleteEmployee.java

Output:

Case 1: Employee id not exist in XML file.

Figure 3

Case 2: Employee id exist in XML file.

Figure 4

employee.xml

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<Employees>
<Employee id="2">
<name>Bhavna</name>
<gender>female</gender>
<age>20</age>
<role>Student</role>
</Employee>
</Employees>

Download Project

Click here for more questions on DOM Parser.

References:

https://docs.oracle.com/javase/7/docs/api/javax/xml/parsers/DocumentBuilderFactory.html
https://docs.oracle.com/javase/7/docs/api/javax/xml/parsers/DocumentBuilder.html

https://docs.oracle.com/javase/7/docs/api/org/w3c/dom/Document.html

https://docs.oracle.com/javase/7/docs/api/org/w3c/dom/Element.html

https://docs.oracle.com/javase/7/docs/api/javax/xml/transform/TransformerFactory.html

https://docs.oracle.com/javase/7/docs/api/javax/xml/transform/Transformer.html

https://docs.oracle.com/javase/7/docs/api/java/io/File.html

https://docs.oracle.com/javase/7/docs/api/javax/xml/transform/dom/DOMSource.html

https://docs.oracle.com/javase/7/docs/api/javax/xml/transform/stream/StreamResult.html

Thank you friends, I hope you have clearly understood the solution of this problem. If you have any doubt, suggestion or query please feel free to comment below. You can also discuss this solution in our forum.

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