Generating an XML representation of arbitrary Java objects

Question

Hi. Just for fun, I'm attempting to write some code which creates an XML representation of an arbitrary java object using reflection. The idea is that only properties with get/set methods should come through in the XML.
Here is the code:
package com.uhg.aarp.compas.persistence.common.xml;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.FactoryConfigurationError;
import javax.xml.parsers.ParserConfigurationException;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.w3c.dom.Document;
import org.w3c.dom.DOMException;
import org.w3c.dom.Node;
import java.util.Stack;
public class XMLDAO {
     public static String getXMLWithHeader(Object obj){
          return "<?xml version=\"0\"?>" + getXML(obj);
      * Returns an XML representation of an arbitrary object
     public static String getXML(Object obj){
          StringBuffer buffer = new StringBuffer();
          AccessorMethod[] accessorMethods = getAccessorMethods(obj);
          buffer.append("<" + obj.getClass().getName() + ">\n");
          //List
          if(obj instanceof List){
               List objList = (List)obj;
               Iterator iterator = objList.iterator();
               while(iterator.hasNext()){                              
                    buffer.append(getXML(iterator.next()));
          else{
               for(int i = 0; i < accessorMethods.length; i++){
                    Object fieldObj = null;
                    try{
                         fieldObj = accessorMethods.invoke();
                         1. Primitive Wrapper or String(base case)
                         if(fieldObj instanceof Integer || fieldObj instanceof Float || fieldObj instanceof Double
                              || fieldObj instanceof Long || fieldObj instanceof String){
                              buffer.append("<" + accessorMethods[i].getAccessorFieldName() + ">");
                              buffer.append(accessorMethods[i].invoke());
                              buffer.append("</" + accessorMethods[i].getAccessorFieldName() + ">\n");
                         else if(fieldObj instanceof Object[]){
                              buffer.append("<" + accessorMethods[i].getAccessorFieldName() + ">\n");
                              Object[] fieldArray = (Object[])fieldObj;
                              for(int j = 0; j < fieldArray.length; j++)
                                   buffer.append(getXML(fieldArray[i]));
                              buffer.append("</" + accessorMethods[i].getAccessorFieldName() + ">\n");
                    }catch(Exception e){
                         System.out.println("Couldn't invoke method: " + accessorMethods[i].getName());
          buffer.append("</" + obj.getClass().getName() + ">\n");
          return buffer.toString();
     * Returns the Object representation for the XML - used to rebuild Java objects
     * converted to XML by XMLDAO.getXML().
     public static Object getObject(String xmlString) throws ParserConfigurationException,
          SAXException, IOException{
          //the root element is the class name
          DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
          DocumentBuilder builder = factory.newDocumentBuilder();
          Document document = builder.parse(xmlString);
          Stack objectStack = new Stack();
          return getObject(document);
     private static Object getObject(Node n){
          //every document is either an object or a bean property
          //all bean properties have values
          //no object has a value, it can only have bean properties
          //the base case occurs when the document has a value
          String nodeName = n.getNodeName();
          if(n.getNodeValue() == null){
               System.out.println("node " + nodeName + " is an object");
          else{
               System.out.println("node " + nodeName + " is a bean property");
          return null;
     * Returns all of the "getter" methods for the given object
     private static AccessorMethod[] getAccessorMethods(Object obj){
          Class theClass = obj.getClass();
          Method[] objMethods = theClass.getMethods();
          ArrayList methodList = new ArrayList();
          for(int i = 0; i < objMethods.length; i++){
               try{
                    methodList.add(new AccessorMethod(obj, objMethods[i]));
               }catch(IllegalArgumentException e){}
          return (AccessorMethod[])methodList.toArray(new AccessorMethod[methodList.size()]);
     * Invokes the specified "getter" method and returns the result as an Object
     private Object invokeAccessorMethod(Object obj, Method m) throws IllegalAccessException,
          InvocationTargetException{
          return m.invoke(obj, null);
package com.uhg.aarp.compas.persistence.common.xml;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
* Represents an AccessorMethod (i.e. getField()) on an Object
public class AccessorMethod{
     private Object obj;
     private Method m;
     private String accessorFieldName;
     * Constructor for AccessorMethod
     public AccessorMethod(Object obj, Method m) throws IllegalArgumentException{
          1. Method name starts with get
          2. Method name does not equal get
          3. Method takes no arguments
          4. Method return type is not void
          String methodName = m.getName();
          if(methodName.indexOf("get") != 0 || methodName.length() == 3 &&
               m.getParameterTypes().length != 0 && m.getReturnType() != null){
               throw new IllegalArgumentException("Not a valid getter method " + methodName);
          this.obj = obj;
          this.m = m;
          String tempName = m.getName().substring(3, m.getName().length());
          this.accessorFieldName = Character.toLowerCase(tempName.charAt(0)) + tempName.substring(1, tempName.length());
     public Object invoke() throws IllegalAccessException, InvocationTargetException{
          return m.invoke(obj, null);
     * Gets the m
     * @return Returns a Method
     public Method getM() {
          return m;
     * Sets the m
     * @param m The m to set
     public void setM(Method m) {
          this.m = m;
     * Gets the accessorFieldName
     * @return Returns a String
     public String getAccessorFieldName() {
          return accessorFieldName;
     * Sets the accessorFieldName
     * @param accessorFieldName The accessorFieldName to set
     public void setAccessorFieldName(String accessorFieldName) {
          this.accessorFieldName = accessorFieldName;
     * Gets the obj
     * @return Returns a Object
     public Object getObj() {
          return obj;
     * Sets the obj
     * @param obj The obj to set
     public void setObj(Object obj) {
          this.obj = obj;
     public String getName(){
          return this.m.getName();
I'm having some trouble figuring out how to implement the XMLDAO.getObject(Node n) method. I was thinking of maintaining a Stack of the previous Objects as I traverse the DOM, but I think that might be unnecessary work. Basically I'm wondering how I determine what the last "object" is in the DOM from any given node. Anyone have any input?

Answer 1

I think the end of my post got cut off:
I'm having some trouble figuring out how to implement the XMLDAO.getObject(Node n) method. I was thinking of maintaining a Stack of the previous Objects as I traverse the DOM, but I think that might be unnecessary work. Basically I'm wondering how I determine what the last "object" is in the DOM from any given node. Anyone have any input?