Obter informações de arquivo XML

<?xml version="1.0" encoding="utf-8"?>
<lom xmlns="http://www.imsglobal.org/xsd/imsmd_rootv1p2p1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.imsglobal.org/xsd/imsmd_rootv1p2p1 imsmd_rootv1p2p1.xsd">
	<general>
		<title>
			<langstring xml:lang="x-none">KS3Sci Behaviour</langstring>
		</title>
		<catalogentry>
			<catalog>JSH</catalog>
			<entry>
				<langstring xml:lang="x-none">JSH3SCQ41</langstring>
			</entry>
		</catalogentry>
		<language>en</language>
		<description>
			<langstring xml:lang="x-none">This is a science quiz containing ten interactive questions.</langstring>
		</description>
		<keyword>
			<langstring xml:lang="x-none">test,interactive,jsh,quiz</langstring>
		</keyword>
	</general>
	<lifecycle>
		<version>
			<langstring xml:lang="x-none">1.0</langstring>
		</version>
		<status>
			<source>
				<langstring xml:lang="x-none">LOMv1.0</langstring>
			</source>
			<value>
				<langstring xml:lang="x-none">Final</langstring>
			</value>
		</status>
	</lifecycle>
	<metametadata>
		<metadatascheme>ADL SCORM 1.2</metadatascheme>
	</metametadata>
	<technical>
		<format>text/html</format>
		<location>Blank.htm</location>
	</technical>
	<educational>
		<learningresourcetype>
			<source>
				<langstring xml:lang="x-none">LOMv1.0</langstring>
			</source>
			<value>
				<langstring xml:lang="x-none">Exercise</langstring>
			</value>
		</learningresourcetype>
	</educational>
	<rights>
		<cost>
			<source>
				<langstring xml:lang="x-none">LOMv1.0</langstring>
			</source>
			<value>
				<langstring xml:lang="x-none">yes</langstring>
			</value>
		</cost>
		<copyrightandotherrestrictions>
			<source>
				<langstring xml:lang="x-none">LOMv1.0</langstring>
			</source>
			<value>
				<langstring xml:lang="x-none">yes</langstring>
			</value>
		</copyrightandotherrestrictions>
		<description>
			<langstring xml:lang="x-none">Subject to copyright restrictions.</langstring>
		</description>
	</rights>
	<classification>
		<purpose>
			<source>
				<langstring xml:lang="x-none">LOMv1.0</langstring>
			</source>
			<value>
				<langstring xml:lang="x-none">Educational Objective</langstring>
			</value>
		</purpose>
		<description>
			<langstring xml:lang="x-none">This science quiz covers the topic of human and animal behaviour.</langstring>
		</description>
		<keyword>
		<langstring xml:lang="x-none">science,test,questions,behaviour,learned,innate,instincts,imitating,mimic,psychology,ethology</langstring>
	</keyword>
	</classification>
</lom>

Ou seja, queria pegar os valores science,test,questions,behaviour,learned,innate,instincts,imitating,mimic,psychology,ethology.

Entretanto, com algumas restrições:

-Um mesmo arquivo pode ter várias tags ;

-Cada tag pode ter várias tags ;

-Preciso pegar esses valores de forma separada pelas vírgulas.

package testPackage;
import java.util.Vector;
import javax.xml.parsers.*;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;

public class LOXmlReader {
	private String xmlPathName;

	public LOXmlReader(String xmlPathName){
		this.xmlPathName = xmlPathName;
	}
	
	public Vector readLOTag() throws Exception{
		DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
		DocumentBuilder db = dbf.newDocumentBuilder();
		Document doc = db.parse(this.xmlPathName);
		
		Element element = doc.getDocumentElement();
		
		NodeList classificationNode = element.getElementsByTagName("classification");
		
		Vector classificationTagValues = new Vector();
		
		//Percorre cada elemento classification encontrado.
		for (int i=0; i<classificationNode.getLength();i++){
			Element classificationTag = (Element) classificationNode.item(i);

			//Pega as dados cadastrados na tag keyword da tag classification atual
			String keyword = getChildTagValue(classificationTag,"keyword");
			
			//Cria uma nova instância do LOContent encontrado
			LOContent loContent = new LOContent(keyword);
			classificationTagValues.addElement(loContent);
		}
		return classificationTagValues;
	}
	
	private String getChildTagValue(Element element, String tagName) throws Exception{
		NodeList children = element.getElementsByTagName(tagName);
		if (children==null){
			return null;
		}
		
		Element child = (Element) children.item(0);
		if (child==null){
			return null;
		}
		return child.getFirstChild().getNodeValue();
	}
}