Home » Core Java » xml » DOM » Add comment to DOM document

About Byron Kiourtzoglou

Byron Kiourtzoglou
Byron is a master software engineer working in the IT and Telecom domains. He is an applications developer in a wide variety of applications/services. He is currently acting as the team leader and technical architect for a proprietary service creation and integration platform for both the IT and Telecom industries in addition to a in-house big data real-time analytics solution. He is always fascinated by SOA, middleware services and mobile development. Byron is co-founder and Executive Editor at Java Code Geeks.

Add comment to DOM document

This is an example of how to add comments to a DOM Document. We have implemented a method, that is void prettyPrint(Document xml), in order to convert a DOM into a formatted XML String. Adding comments to a DOM Document implies that you should:

  • Obtain a new instance of a DocumentBuilderFactory, that is a factory API that enables applications to obtain a parser that produces DOM object trees from XML documents.
  • Set the parser produced so as not to validate documents as they are parsed, using setValidating(boolean validating) API method of DocumentBuilderFactory, with validating set to false.
  • Create a new instance of a DocumentBuilder, using newDocumentBuilder() API method of DocumentBuilderFactory.
  • Parse the FileInputStream with the content to be parsed, using parse(InputStream is) API method of DocumentBuilder. This method parses the content of the given InputStream as an XML document and returns a new DOM Document object.
  • Get the Document Element using getDocumentElement() API method of Document.
  • Create a new Comment, using createComment(String data) API method of Document.
  • Get the parent node of the Document Element, and use insertBefore(Node newChild, Node refChild) API method of Node, for the parent node, to insert the comment before the specified child of the parent node.
  • Call void prettyPrint(Document xml) method of the example. The method gets the xml Document and converts it into a formatted xml String, after transforming it with specific parameters, such as encoding. The method uses a Transformer, that is created using newTransformer() API method of TransformerFactory. The Transformer is used to transform a source tree into a result tree. After setting specific output properties to the transformer, using setOutputProperty(String name, String value) API method of Transformer, the method uses it to make the transformation, with transform(Source xmlSource, Result outputTarget) API method of Transformer. The parameters are the DOMSource with the DOM node and the result that is a StreamResult created from a StringWriter.

Let’s take a look at the code snippet that follows:  

package com.javacodegeeks.snippets.core;

import java.io.File;
import java.io.FileInputStream;
import java.io.StringWriter;
import java.io.Writer;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Comment;
import org.w3c.dom.Document;
import org.w3c.dom.Element;

public class AddCommentToDOMDocument {
	
public static void main(String[] args) throws Exception {
		
		DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
		dbf.setValidating(false);
		DocumentBuilder db = dbf.newDocumentBuilder();
		
		Document doc = db.parse(new FileInputStream(new File("in.xml")));
		
		Element element = doc.getDocumentElement();
		Comment comment = doc.createComment("This is a comment");
		element.getParentNode().insertBefore(comment, element);
		
		prettyPrint(doc);
		
	}
	
	public static final void prettyPrint(Document xml) throws Exception {
		Transformer tf = TransformerFactory.newInstance().newTransformer();
		tf.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
		tf.setOutputProperty(OutputKeys.INDENT, "yes");
		Writer out = new StringWriter();
		tf.transform(new DOMSource(xml), new StreamResult(out));
		System.out.println(out.toString());
	}

}

Input:

<?xml version="1.0" encoding="UTF-8"?>
<rss version="2.0">
	<channel>
		<title>Java Tutorials and Examples</title>
		<item>
			<title><![CDATA[Java Tutorials]]></title>
			<link>http://www.javacodegeeks.com/</link>
		</item>
	</channel>
</rss>

Output:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!--This is a comment-->
<rss version="2.0">
	<channel>
		<title>Java Tutorials and Examples</title>
		<item>
			<title><![CDATA[Java Tutorials]]></title>
			<link>http://www.javacodegeeks.com/</link>
		</item>
	</channel>
</rss>

  
This was an example of how to add comments to a DOM Document in Java.

(No Ratings Yet)
2 Comments Views Tweet it!

Do you want to know how to develop your skillset to become a Java Rockstar?

Subscribe to our newsletter to start Rocking right now!

To get you started we give you our best selling eBooks for FREE!

 

1. JPA Mini Book

2. JVM Troubleshooting Guide

3. JUnit Tutorial for Unit Testing

4. Java Annotations Tutorial

5. Java Interview Questions

6. Spring Interview Questions

7. Android UI Design

 

and many more ....

 

Receive Java & Developer job alerts in your Area

 

2
Leave a Reply

avatar
2 Comment threads
0 Thread replies
0 Followers
 
Most reacted comment
Hottest comment thread
2 Comment authors
Alisha RossGiselle aga Recent comment authors
  Subscribe  
newest oldest most voted
Notify of
Giselle aga
Guest

Needed to compose you a very little word to thank you yet again regarding the nice suggestions you’ve contributed here.

Alisha Ross
Guest

Great tremendous things here. I’m very glad to look your article. Thank you so much and i am taking a look ahead to contact you. Will you please drop me a mail?