Java Tutorial/XML/CDATA

http://jexp.ru/index.php/Java_Tutorial/XML/CDATA
Converting CDATA Nodes into Text Nodes While Parsing an XML File

DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
factory.setCoalescing(true);
Document doc = factory.newDocumentBuilder().parse(new File("infilename.xml"));

java - Processing CDATA from XML via DOM parser - Stack Overflow

java - Processing CDATA from XML via DOM parser - Stack Overflow
I'm suspecting that your problem is in the following line of code from the getTagValue method:

Node nValue = (Node) nlList.item(0);

You are always getting the first child! But you might have more than one.
The following example has 3 children: text node "detail ", CDATA node "with cdata" and text node " here":

<Details>detail <![CDATA[with cdata]]> here</Details>

If you run your code, you get only "detail ", you loose the rest.
The following example has 1 child: a CDATA node "detail with cdata here":

<Details><![CDATA[detail with cdata here]]></Details>

If you run your code, you get everything.
But the same example as above written this way:

<Details>     <![CDATA[detail with cdata here]]>  </Details>

now has 3 children because the spaces and line feeds are picked up as text nodes. If you run your code you get the first empty text node with a line feed, you loose the rest.
You either have to loop through all children (no matter how many) and concatenate the value of each to get the full result, or if it's not important for you to differentiate between plain text and text inside CDATA, then set the coalescing property on the document builder factory first:

DocumentBuilderFactory docFactory = DocumentBuilderFactory.newInstance();  docFactory.setCoalescing(true);

Coalescing specifies that the parser produced by this code will convert CDATA nodes to Text nodes and append it to the adjacent (if any) text node. By default the value of this is set to false.
Read full article from java - Processing CDATA from XML via DOM parser - Stack Overflow

Get character data (CDATA) from xml document

http://www.java2s.com/Code/Java/XML/GetcharacterdataCDATAfromxmldocument.htm
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.w3c.dom.CharacterData;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

public class Main {
  public static void main(String[] args) throws Exception {
    File file = new File("data.xml");
    DocumentBuilder builder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
    Document doc = builder.parse(file);

    NodeList nodes = doc.getElementsByTagName("topic");
    for (int i = 0; i < nodes.getLength(); i++) {
      Element element = (Element) nodes.item(i);
      NodeList title = element.getElementsByTagName("title");
      Element line = (Element) title.item(0);
      System.out.println("Title: " + getCharacterDataFromElement(line));
    }
  }
  public static String getCharacterDataFromElement(Element e) {
    Node child = e.getFirstChild();
    if (child instanceof CharacterData) {
      CharacterData cd = (CharacterData) child;
      return cd.getData();
    }
    return "";
  }
}