import javax.xml.parsers.*;
import org.xml.sax.*;
import org.w3c.dom.*;
import java.io.*;
import java.nio.file.*;
import static org.w3c.dom.Node.*;                                      // For node type constants

public class TryDOM implements ErrorHandler {
  public static void main(String args[]) {
    if(args.length == 0) {
      System.out.println("No file to process." + "Usage is:\njava TryDOM \"filename\"");
      System.exit(1);
    }
    DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance();
    builderFactory.setNamespaceAware(true);                            // Set namespace aware
    builderFactory.setValidating(true);                                // & validating parser
    builderFactory.setIgnoringElementContentWhitespace(true);

    DocumentBuilder builder = null;
    try {
      builder = builderFactory.newDocumentBuilder();                   // Create the parser
      builder.setErrorHandler(new TryDOM());                           //Error handler is TryDOM instance
    } catch(ParserConfigurationException e) {
      e.printStackTrace();
      System.exit(1);
    }

    Path xmlFile = Paths.get(args[0]);
    Document xmlDoc = null;
    try (BufferedInputStream in = new BufferedInputStream(Files.newInputStream(xmlFile))){
      xmlDoc = builder.parse(in);
    } catch(SAXException | IOException e) {
      e.printStackTrace();
      System.exit(1);
    }

    DocumentType doctype = xmlDoc.getDoctype();                        // Get the DOCTYPE node
    if(doctype == null) {                                              // If it’s not null...
      System.out.println("DOCTYPE is null");
    } else {                                                           // ...output it
      System.out.println("DOCTYPE node:\n" + doctype.getInternalSubset());
    }

    System.out.println("\nDocument body contents are:");
    listNodes(xmlDoc.getDocumentElement(), " ");                       // Root element & children
  }

  // output a node and all its child nodes
  static void listNodes(Node node, String indent) {
    // List the current node
    String nodeName = node.getNodeName();
    System.out.println(indent + " Node: " + nodeName);
    short type =node.getNodeType();
    System.out.println(indent+" Node Type: " + nodeType(type));
    if(type == TEXT_NODE){
      System.out.println(indent + " Content is: " + ((Text)node).getWholeText());
    }

    NodeList list = node.getChildNodes();                              // Get the list of child nodes
    if(list.getLength() > 0) {                                         // If there are some...
      //...list them & their children...
      // ...by calling listNodes() for each
      System.out.println(indent+" Child Nodes of "+nodeName+" are:");
      for(int i = 0 ; i < list.getLength() ; ++i) {
        listNodes(list.item(i),indent + "  ");
      }
    }
  }

  // Method to identify the node type
  static String nodeType(short type) {
    switch(type) {
      case ELEMENT_NODE:                return "Element";
      case DOCUMENT_TYPE_NODE:          return "Document type";
      case ENTITY_NODE:                 return "Entity";
      case ENTITY_REFERENCE_NODE:       return "Entity reference";
      case NOTATION_NODE:               return "Notation";
      case TEXT_NODE:                   return "Text";
      case COMMENT_NODE:                return "Comment";
      case CDATA_SECTION_NODE:          return "CDATA Section";
      case ATTRIBUTE_NODE:              return "Attribute";
      case PROCESSING_INSTRUCTION_NODE: return "Attribute";
    }
    return "Unidentified";
  }

  public void fatalError(SAXParseException spe) throws SAXException {
    System.out.println("Fatal error at line " + spe.getLineNumber());
    System.out.println(spe.getMessage());
    throw spe;
  }

  public void warning(SAXParseException spe) {
    System.out.println("Warning at line " + spe.getLineNumber());
    System.out.println(spe.getMessage());
  }

  public void error(SAXParseException spe) {
    System.out.println("Error at line " + spe.getLineNumber());
    System.out.println(spe.getMessage());
  }
}