SodhanaLibrary

This tutorial teaches how to read and differentiate different type of XML Nodes. You might also interested to read parsing JSON tutorial  at Read JSON with JAVA using Google-gson library.

There are 3 important XML data parts.

1. Element - Elements have tags. In above example bookstore, book, title, author are elements
2. Attribute - These are attributes for Elements. In above example category is attribute.
3. Text - Simple text surrounded by tags

Program Flow :

1. Read ROOT Element as Node
2. If it is Text, go to 3rd step else go to 4th step.
3. print text value
4. If it is Element, print all attributes and list children and send them to 2nd step

XOM Java Library :

By using traditional DOM and SAX parser we cannot implement above program flow. We need XOM parser. You can download XOM at http://www.cafeconleche.org/XOM/xom-1.2.10.jar

Java Code :

import java.io.*;
import java.nio.charset.StandardCharsets;
import nu.xom.*;

public class XOMParserXML {

  public static void main(String[] args) {
    String xml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?><bookstore>" + "\n<!-- Servlets --><book category=\"CHILDREN\">"
            + "\n    <title>Harry Potter</title>"
            + "\n    <author>J K. Rowling</author>"
            + "\n    <year>2005</year>" + "\n    <price>29.99</price>"
            + "\n  </book>" + "\n  <book category=\"WEB\">"
            + "\n    <title>Learning XML</title>"
            + "\n    <author>Erik T. Ray</author>"
            + "\n    <year>2003</year>" + "\n    <price>39.95</price>"
            + "\n  </book>" + "\n</bookstore>";
    System.out.println(xml);
    
    // Remove All Spaces
    xml = trimSpaces(xml);
    try {
      Builder builder = new Builder();
      InputStream stream = new ByteArrayInputStream(xml.getBytes(StandardCharsets.UTF_8));
      Document doc = builder.build(stream);
      // Get Root Element
      Element root = doc.getRootElement();
      // List Children for Root Element
      listChildren(root, 0);      
    }
    catch (ParsingException ex) { 
      System.out.println(args[0] + " is not well-formed.");
      System.out.println(ex.getMessage());
    }  
    catch (IOException ex) { 
      System.out.println(ex);
    }  
  
  }
  
  public static void listChildren(Node current, int depth) {
   
    printSpaces(depth);
    String data = "";
    // If it is element
    if (current instanceof Element) {
        Element temp = (Element) current;
        data = ": " + temp.getQualifiedName();
        // print Attributes
        for (int i = 0; i < temp.getAttributeCount(); i++) {
          Attribute attribute = temp.getAttribute(i);
          String attValue = attribute.getValue();
          attValue = attValue.replace('\n', ' ').trim();
          if (attValue.length() >= 20) {
            attValue = attValue.substring(0, 17) + "..."; 
          }
          data += "\r\n    ";
          data += attribute.getQualifiedName();
          data += "=";
          data += attValue;
        }
        System.out.println(current.getClass().getName() + data);
        
        // iterate child nodes
        for (int i = 0; i < current.getChildCount(); i++) {
            listChildren(current.getChild(i), depth+1);
        }
    }
    //If it is text
    else if (current instanceof Text) {
        String value = current.getValue();
        value = value.replace('\n', ' ').trim();
        data = ": " + value;
        System.out.println(current.getClass().getName() + data);
    }
    
  }
 
  // Method to remove all space and new lines
  public static String trimSpaces(String input) {
        BufferedReader reader = new BufferedReader(new StringReader(input));
        StringBuffer result = new StringBuffer();
        try {
            String line;
            while ( (line = reader.readLine() ) != null)
                result.append(line.trim());
            return result.toString();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
   }
  
  // Method to print spaces
  private static void printSpaces(int n) {
    for (int i = 0; i < n; i++) {
      System.out.print("  "); 
    }
    
  }

}