Java Convert String to XML Document and XML Document to String

Sometimes while programming in java, we get String which is actually an XML and to process it, we need to convert it to XML Document (org.w3c.dom.Document). Also for debugging purpose or to send to some other function, we might need to convert Document object to String. Here I am providing two utility functions.

1. Document convertStringToDocument(String xmlStr): This method will take input as String and then convert it to DOM Document and return it. We will use InputSource and StringReader for this conversion.
2. String convertDocumentToString(Document doc): This method will take input as Document and convert it to String. We will use Transformer, StringWriter and StreamResult for this purpose.

package com.journaldev.xml;

import java.io.StringReader;
import java.io.StringWriter;

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

import org.w3c.dom.Document;
import org.xml.sax.InputSource;

public class StringToDocumentToString {

    public static void main(String[] args) {
        final String xmlStr = "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"yes\"?>\n"+
                                "<Emp id=\"1\"><name>Pankaj</name><age>25</age>\n"+
                                "<role>Developer</role><gen>Male</gen></Emp>";
        Document doc = convertStringToDocument(xmlStr);
        
        String str = convertDocumentToString(doc);
        System.out.println(str);
    }

    private static String convertDocumentToString(Document doc) {
        TransformerFactory tf = TransformerFactory.newInstance();
        Transformer transformer;
        try {
            transformer = tf.newTransformer();
            // below code to remove XML declaration
            // transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
            StringWriter writer = new StringWriter();
            transformer.transform(new DOMSource(doc), new StreamResult(writer));
            String output = writer.getBuffer().toString();
            return output;
        } catch (TransformerException e) {
            e.printStackTrace();
        }
        
        return null;
    }

    private static Document convertStringToDocument(String xmlStr) {
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();  
        DocumentBuilder builder;  
        try  
        {  
            builder = factory.newDocumentBuilder();  
            Document doc = builder.parse( new InputSource( new StringReader( xmlStr ) ) ); 
            return doc;
        } catch (Exception e) {  
            e.printStackTrace();  
        } 
        return null;
    }

}

When we run above program, we get the same String output that we used to create DOM Document.

<?xml version="1.0" encoding="UTF-8"?><Emp id="1"><name>Pankaj</name><age>25</age>
<role>Developer</role><gen>Male</gen></Emp>

You can use replaceAll("\n|\r", "") to remove new line characters from String and get it in compact format.