Adding linebreak in xml file before root node

Question

I am trying to add line break after my comments above the root node in XML document.

I need something like this:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!--DO NOT EDIT THIS FILE-->
<projects>
</projects>

But What I was able to get is this(Line break inside the root but I need line break after the comment):

    <?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!--DO NOT EDIT THIS FILE--><projects>

</projects>

I need to add the line break just after my comment. Is there a way to do this?

My code:

import java.io.File;
import java.io.FileInputStream;

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;
import org.w3c.dom.Text;

public class XMLNewLine {
    /**
     * @param args
     */
    public static void main(String[] args) {
        System.out.println("Adding comment..");

        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();

        dbf.setValidating(false);
        DocumentBuilder db;

        try {
            Document doc;
            StreamResult result;
            result = new StreamResult(new File("abc.xml"));
            db = dbf.newDocumentBuilder();
            doc = db.parse(new FileInputStream(new File("abc.xml")));

            Element element = doc.getDocumentElement();
            Text lineBreak = doc.createTextNode("\n");

            element.appendChild(lineBreak);
            Comment comment = doc
                    .createComment("DO NOT EDIT THIS FILE");
            element.getParentNode().insertBefore(comment, element);
            doc.getDocumentElement().normalize();
            TransformerFactory transformerFactory = TransformerFactory
                    .newInstance();
            Transformer transformer = transformerFactory.newTransformer();
            DOMSource source = new DOMSource(doc);
            transformer.setOutputProperty(OutputKeys.INDENT, "yes");
            transformer.transform(source, result);

        } catch (Exception e) {
            // TODO Auto-generated catch block

        }

    }
}

Answer 1

Revisiting this after some time because I had the same issue. I found another solution that does not need to buffer the output in a String:

1. Write only the XML-declaration by passing an empty document. This will also append a linebreak.

2. Write the document content without XML-declaration

Code:

StreamResult streamResult = new StreamResult(writer);
// output XML declaration with an empty document
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "no");
transformer.transform(new DOMSource(), streamResult);
// output the document without XML declaration
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
transformer.transform(new DOMSource(doc), streamResult);

Answer 2

You can achieve this by not adding the comment node to your document, but instead partially transforming your document. First transform your own XML processing instruction and comment separately, and then the rest of document:

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document doc = db.parse(new FileInputStream(new File("abc.xml")));

Result output = new StreamResult(new File("abc.xml"));
Source input = new DOMSource(doc);


// xml processing instruction and comment node
ProcessingInstruction xmlpi = doc.createProcessingInstruction("xml", "version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"");
Comment comment = doc.createComment("DO NOT EDIT THIS FILE");

// first transform the processing instruction and comment
transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
transformer.transform(new DOMSource(xmlpi), output);
transformer.transform(new DOMSource(comment), output);
// then the document
transformer.transform(input, output);

Answer 3

There is a JDK bug concerning this. It was not fixed (as you would expect) because that would likely cause many problems to users' existing applications.

Adding the following output property fixes this:

transformer.setOutputProperty("http://www.oracle.com/xml/is-standalone", "yes");

Answer 4

Had the same issue. I solved it by putting the comment inside the root element. Not exactly the same, but I think acceptable.

Answer 5

This is my solution. I just take writer and write to it declaration and the header comment. After that I disable declaration in transformer this way

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

All code:

public static String xmlToTree(String xml, String headerComment) {
        try (StringReader reader = new StringReader(xml)) {
            StreamResult result = new StreamResult(new StringWriter());
            result.getWriter().write("<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?>\n");
            result.getWriter().write(headerComment + "\n");
            
            Transformer transformer = TransformerFactory.newInstance().newTransformer();
            transformer.setOutputProperty(OutputKeys.INDENT, "yes");
            transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
            transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
            transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "4");
            
            StreamSource source = new StreamSource(reader);
            transformer.transform(source, result);

            String xmlTree = result.getWriter().toString();
            return xmlTree;
        } catch (Exception ex) {
            ex.printStackTrace();
            return null;
        }
    }