ParserImpl for DOM

[Bhasker Reddy]

iS there code examples for implementing DOM parser.
I need implementation for these methods to extract values from XML files using DOM parser
// Methods
public Node parse(File fileName) { return null;}
public Node[] getChildren(Node node) { return null;}
public Node[] getChildByName(Node node, String name) { return null;}
public Node getFirstChildByName(Node node, String name) { return null;}
public String[] getNodeValueByName(Node node, String name) { return null;}
public String getFirstNodeValueByName(Node node, String name) { return null;}
public Attr[] getAttributes(Node node) { return null;}
public String getAttributesByName(Node node, String name) { return null;}
public Node[] getNodeDrilled(Node node, String[] path) { return null;}
public Node getFirstNodeDrilled(Node _node, String[] _path) { return null;}
public void fillObject(Node node, String[] path, Object objToFill) { }

[Lasse Koskela]

Are you really implementing your own DOM parser?
Why can't you use an existing, time-tested implementation such as Apache Xerces or the one that comes with J2SE 1.4?

[Bhasker Reddy]

I am using DOM parser. But I am trying to write some methods to extract values.
package nortel.xml.datatypes;

import java.io.File;
import org.w3c.dom.Attr;
import org.w3c.dom.Node;
import org.w3c.dom.*;
import java.util.*;

import org.xml.sax.*;
//import org.jdom.input.*;
import org.apache.xerces.parsers.DOMParser;
import java.io.*;
import java.util.logging.FileHandler;
import javax.xml.parsers.*;





/**
* <p>Title: </p>
* <p>Description: </p>
* <p>Copyright: Copyright (c) 2004</p>
* <p>Company: </p>
* @author not attributable
* @version 1.0
*/

public class ParserImp {
public ParserImp() {
}


// Methods
public Node parse(File fileName) {
try{
/*
Document doc = null ;
InputStream ins = new FileInputStream( f );
InputStreamReader isr = new InputStreamReader( ins, "UTF-8" );
LineNumberReader lnr = new LineNumberReader( isr );
InputSource isrc = new InputSource( lnr );
try {
DocumentBuilderFactory fac = DocumentBuilderFactory.newInstance();
fac.setValidating( false ); // default is false
fac.setIgnoringComments( true );
fac.setIgnoringElementContentWhitespace( true );
DocumentBuilder builder = fac.newDocumentBuilder();
// doc = builder.parse( f );
doc = builder.parse( isrc );
*/

InputStream ins = new FileInputStream( fileName );
InputStreamReader isr = new InputStreamReader( ins, "UTF-8" );
LineNumberReader lnr = new LineNumberReader( isr );
InputSource isrc = new InputSource( lnr );
DocumentBuilderFactory fac = DocumentBuilderFactory.newInstance();
fac.setValidating(false);
fac.setIgnoringComments(true);
fac.setIgnoringElementContentWhitespace( true );
DocumentBuilder builder = fac.newDocumentBuilder();
Document doc = builder.parse(isrc);
Node node = doc.getFirstChild();
// Node node = null;
// Node node = doc.getParentNode();

System.out.println("node type" + node.getNodeType());
System.exit(-1);
System.out.println("$$$$$$$$$$$$$$$NODE.NODENAME:::::::" + fileName);
return node;


//* To read from string
/* StringReader stringreader = new StringReader(fileName.toString());
InputSource stringInputSource = new InputSource(stringreader);

DOMParser parser = new DOMParser();
parser.parse(stringInputSource);
Document document = parser.getDocument();
Node node = document.getParentNode();
return node;*/

}
catch (Exception e) {
System.err.println("XML Parser Exception: " + e.getMessage());
e.printStackTrace(System.err);
}

return null;
}
public static Node[] getChildren(Node node) {
System.out.println("Node:getNodeNAme::::" + node.getNodeName());
NodeList nodeList = node.getParentNode().getChildNodes();
Node[] nodeArray = new Node[nodeList.getLength()];
for (int idx=0; idx<nodeList.getLength(); idx++){
nodeArray[idx] = nodeList.item(idx);
}
return nodeArray;
}
public static Node[] getChildByName(Node node, String name) {
Node[] nodeArray = getChildren(node);
ArrayList arrList = new ArrayList();
for (int idx=0; idx<nodeArray.length; idx++){
if (nodeArray[idx].getParentNode().getNodeName().equals(name)){
arrList.add(nodeArray[idx]);
}
}
Node[] nodeArrayRet = new Node[arrList.size()];
ListIterator itr = arrList.listIterator();
int idx=0;
while (itr.hasNext()){
nodeArrayRet[idx] = (Node)itr.next();
idx++;
}

return nodeArrayRet;
}
public static Node getFirstChildByName(Node node, String name) {
Node[] nodeArray = getChildren(node);
for (int idx=0; idx<nodeArray.length; idx++){
if (nodeArray[idx].getParentNode().getNodeName().equals(name))
return nodeArray[idx];
}

return null;
}
public static String[] getNodeValueByName(Node node, String name) { return null;}

public static String getFirstNodeValueByName(Node node, String name) {
Node[] nodeArray = getChildren(node);
for (int idx=0; idx<nodeArray.length; idx++){
if (nodeArray[idx].getParentNode().getNodeName().equals(name))
return nodeArray[idx].getParentNode().getNodeValue();
}
return null;
}

public Attr[] getAttributes(Node node) { return null;}
public String getAttributesByName(Node node, String name) { return null;}
public Node[] getNodeDrilled(Node node, String[] path) { return null;}
public Node getFirstNodeDrilled(Node _node, String[] _path) { return null;}
public void fillObject(Node node, String[] path, Object objToFill) { }


}

It's crazy. I cannot understand it. I tried to extract node values from xml file. First by using parse method, get the Main node(Document node) and
then pass that node to a datatype class, that inturn calls the methods in these classes to get values.
Can you guys help me out.

[William Brogden]

Read the documentation in the org.w3c.dom.Node JavaDocs. Many types of node have null for the node value and this frequently trips people up.