Trying to build XML file with iterator in java

Question

Ive written some code that creates an XML file from my System Properties in java. It works exactly how I want it to but I really (really) dont like how I ended up just using like 5 if statements to get it to work since I noticed none of the properties go beyond 4 delimited substrings anyways. Id much prefer using an iterator and some kind of hasNext() method to continue appending onto elements until the end of the string but I couldn't work anything out. I couldn't find a way to append the newest tag onto the last one in a loop/ add the value to the end of the elements.

This is what I currently have as a quick fix to get the program running.

Document doc = docBuilder.newDocument();
    Element rootElement = doc.createElement("JAVA");
    doc.appendChild(rootElement);

    Iterator it = hm.entrySet().iterator();
    while (it.hasNext()) 
    {
        Map.Entry entry = (Map.Entry) it.next();
        String keyString = (String)entry.getKey();
        String val = (String)entry.getValue();
        java.util.List<String> sa = Arrays.asList(keyString.split("\\."));

        Iterator ait = sa.iterator();

        Element tag = doc.createElement((String) ait.next());
        rootElement.appendChild(tag);

        Element tag2 = null;
        Element tag3 = null;
        Element tag4 = null;
        Element tag5 = null;

        while(ait.hasNext())
        {   
            if(ait.hasNext())
            {    
            tag2 = doc.createElement((String)ait.next());
            tag.appendChild(tag2);
            if(!ait.hasNext())
                tag2.appendChild(doc.createTextNode(val)); 

            }
            if(ait.hasNext())
            {    
            tag3=doc.createElement((String)ait.next());
            tag2.appendChild(tag3);
                if(!ait.hasNext())
                    tag3.appendChild(doc.createTextNode(val)); 
            }
            if(ait.hasNext())
            {    
            tag4=doc.createElement((String)ait.next());
            tag3.appendChild(tag4);
            if(!ait.hasNext())
                tag4.appendChild(doc.createTextNode(val)); 
            }
            if(ait.hasNext())
            {    
            tag5=doc.createElement((String)ait.next());
            tag5.appendChild(tag5);
            if(!ait.hasNext())
                tag5.appendChild(doc.createTextNode(val)); 
            }

        }

    }

    Transformer transformer = null;
    TransformerFactory transformerFactory = TransformerFactory.newInstance();
    try
    {
        DOMSource source = new DOMSource(doc);
        StreamResult result = new StreamResult(new File("XMLtester"));

        transformer = transformerFactory.newTransformer();
        transformer.setOutputProperty(OutputKeys.INDENT, "yes");
        transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");
        transformer.transform(source, result);

    } catch (TransformerConfigurationException e)
    {
        e.printStackTrace();
    } catch (TransformerException e)
    {
        e.printStackTrace();
    }
    catch(NullPointerException e)
    {
        System.out.println("ERROR: " + e.toString());
    }
    System.out.println("File saved!");

If anyone has any ideas on how to make this a little more flexible or elegant so as to take in any number of delimited substrings id appreciate it.

Can you provide example input and output. Thanks.

Adam
– Adam

2014-05-09 05:29:30 +00:00
Commented May 9, 2014 at 5:29 — Adam
– Adam, Commented May 9, 2014 at 5:29

Adam · Accepted Answer · 2014-05-09 05:51:33Z

I think this is what you want.

Element destination = rootElement;
Element tag = null;
while (ait.hasNext()) {
    tag = doc.createElement((String) ait.next());
    destination.appendChild(tag);
    destination = tag;
}
destination.appendChild(doc.createTextNode(val));

Example output:

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<JAVA>
  <java>
    <runtime>
      <name>Java(TM) SE Runtime Environment</name>
    </runtime>
  </java>
  <sun>
    <boot>
      <library>
        <path>/Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home/jre/lib</path>
      </library>
    </boot>
  </sun>
  <java>
    <vm>
      <version>23.0-b19</version>
    </vm>
  </java>
  <user>
    <country>
      <format>GB</format>
    </country>
  </user>

Full working example:

import java.io.File;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;
import java.util.Map;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.Document;
import org.w3c.dom.Element;

public class StackOverflow23556822 {

    public static void main(String[] args) throws ParserConfigurationException,
            TransformerException {
        DocumentBuilder docBuilder = DocumentBuilderFactory.newInstance()
                .newDocumentBuilder();
        Document doc = docBuilder.newDocument();
        Element rootElement = doc.createElement("JAVA");
        doc.appendChild(rootElement);

        Iterator<?> it = System.getProperties().entrySet().iterator();
        while (it.hasNext()) {
            Map.Entry<?, ?> entry = (Map.Entry<?, ?>) it.next();
            String keyString = (String) entry.getKey();
            String val = (String) entry.getValue();
            List<String> sa = Arrays.asList(keyString.split("\\."));

            Iterator<?> ait = sa.iterator();

            Element destination = rootElement;
            Element tag = null;
            while (ait.hasNext()) {
                tag = doc.createElement((String) ait.next());
                destination.appendChild(tag);
                destination = tag;
            }
            destination.appendChild(doc.createTextNode(val));

        }

        Transformer transformer = null;
        TransformerFactory transformerFactory = TransformerFactory
                .newInstance();
        DOMSource source = new DOMSource(doc);
        StreamResult result = new StreamResult(new File("xml-test.xml"));

        transformer = transformerFactory.newTransformer();
        transformer.setOutputProperty(OutputKeys.INDENT, "yes");
        transformer.setOutputProperty(
                "{http://xml.apache.org/xslt}indent-amount", "2");
        transformer.transform(source, result);

        System.out.println("File saved!");
    }
}

This is perfect. Thanks so much. I tried a number of different approaches but this one never came to me. This is so so much better.
I find pencil and paper works wonders for complicated problems - figure out how you'd do it by-hand first.

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