How to parse an XML file with the DOM API without including whitespaces between XML elements?

In many cases, whitespaces are included in XML fiels before and after XML elements to make the XML file more readable.

For example, the follwoing XML file, User.xml, includes whitespaces:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<!-- Copyright (c) 2017 FYIcenter.com -->
<User>
    <ID>101</ID>
    <BirthDate>1970-01-01+00:01</BirthDate>
    <Name>Frank Y. Ivy</Name>
    <Sex>  Male</Sex>
</User>

If you want the DOM XML parser to ignore whitespaces, you need to do two things:

1, Add DTD (Document Type Definition) to define the element structure as shown in UserDTD.xml:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<!-- Copyright (c) 2017 FYIcenter.com -->
<!DOCTYPE User [
   <!ELEMENT User (ID, BirthDate, Name, Sex)>
   <!ELEMENT ID (#PCDATA)>
   <!ELEMENT BirthDate (#PCDATA)>
   <!ELEMENT Name (#PCDATA)>
   <!ELEMENT Sex (#PCDATA)>
]>

<User>
    <ID>101</ID>
    <BirthDate>1970-01-01+00:01</BirthDate>
    <Name>Frank Y. Ivy</Name>
    <Sex>  Male</Sex>
</User>

2. Tell the parser to ignore whitespaces: setIgnoringElementContentWhitespace(true), as shown in DomXmlParserWhitespace.java:

// Copyright (c) 2017 FYIcenter.com
import java.io.*;
import javax.xml.parsers.*;
import org.w3c.dom.*;

public class DomXmlParserWhitespace {
   static String dot = "............................................................";
   public static void main(String[] args) throws Exception {
      DocumentBuilderFactory f = DocumentBuilderFactory.newInstance();
    f.setIgnoringElementContentWhitespace(Boolean.parseBoolean(args[1]));
    
      DocumentBuilder b = f.newDocumentBuilder();
      Document d = b.parse(new File(args[0]));
      System.out.println("Implementation class:\n   "+d.getClass().getName());
    
      System.out.println("DOM object elements and text contents:");
    Node n = d.getDocumentElement();
    printText(n, 1);
   }
   public static void printText(Node n, int l) {
      String v = "";
      if (n.getNodeType()==Node.TEXT_NODE) v = n.getTextContent();
      System.out.println(dot.substring(0,l)+n.getNodeName()+":"+v);
    NodeList c = n.getChildNodes();
    for (int i=0; i<c.getLength(); i++) {
       printText(c.item(i),l+1);
    }
   }
}

Compile and run the example program, DomXmlParserWhitespace.java, with setIgnoringElementContentWhitespace(false):

>\fyicenter\jdk-1.8.0\bin\javac DomXmlParserWhitespace.java

>\fyicenter\jdk-1.8.0\bin\java DomXmlParserWhitespace UserDTD.xml false

Implementation class:
   com.sun.org.apache.xerces.internal.dom.DeferredDocumentImpl
   
DOM object elements and text contents:
.User:
..#text:

..ID:
...#text:101
..#text:

..BirthDate:
...#text:1970-01-01+00:01
..#text:

..Name:
...#text:Frank Y. Ivy
..#text:

..Sex:
...#text:  Male
..#text:

Run it again with setIgnoringElementContentWhitespace(true):

>\fyicenter\jdk-1.8.0\bin\java DomXmlParserWhitespace UserDTD.xml true

Implementation class:
   com.sun.org.apache.xerces.internal.dom.DeferredDocumentImpl
   
DOM object elements and text contents:
.User:
..ID:
...#text:101
..BirthDate:
...#text:1970-01-01+00:01
..Name:
...#text:Frank Y. Ivy
..Sex:
...#text:  Male

The output tells you that Apache Xerces is able to ignore whitespaces based on the DTD definitions.

⇒ DomXmlSerializer.java - Serialize DOM to XML String

⇐ DomXmlParser.java - Parse XML File with DOM API

⇑ Using XML DOM API with Apache Xerces

⇑⇑ FAQ for Apache Xerces XML Parser