Convert XML file to CSV in java

Question

@Before There will be probably some duplicate questions suggestions, I don\'t think that is the case maybe read this first, I\'ll try to be as brief as possible. Title gives

Answer 1

Here some code that implements the conversion of the XML to CSV using StAX. Although the XML you gave is only an example, I hope that this shows you how to handle the optional elements.

import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamConstants;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import java.io.*;

public class App 
{
    public static void main( String[] args ) throws XMLStreamException, FileNotFoundException
    {
        new App().convertXMLToCSV(new BufferedInputStream(new FileInputStream(args[0])), new BufferedOutputStream(new FileOutputStream(args[1])));
    }

    static public final String ROOT = "root";
    static public final String ITEM = "Item";
    static public final String ITEM_ID = "ItemID";
    static public final String ITEM_DETAILS = "ListingDetails";
    static public final String START_TIME = "StartTime";
    static public final String END_TIME = "EndTime";
    static public final String ITEM_URL = "ViewItemURL";
    static public final String AVERAGES = "averages";
    static public final String AVERAGE_TIME = "AverageTime";
    static public final String AVERAGE_PRICE = "AveragePrice";
    static public final String SEPARATOR = ",";

    public void convertXMLToCSV(InputStream in, OutputStream out) throws XMLStreamException
    {
        PrintWriter writer = new PrintWriter(out);
        XMLStreamReader xmlStreamReader = XMLInputFactory.newInstance().createXMLStreamReader(in);
        convertXMLToCSV(xmlStreamReader, writer);
    }

    public void convertXMLToCSV(XMLStreamReader xmlStreamReader, PrintWriter writer) throws XMLStreamException {
        writer.println("ItemID,StartTime,EndTime,ViewItemURL,AverageTime,AveragePrice");
        xmlStreamReader.nextTag();
        xmlStreamReader.require(XMLStreamConstants.START_ELEMENT, null, ROOT);

        while (xmlStreamReader.hasNext()) {
            xmlStreamReader.nextTag();
            if (xmlStreamReader.isEndElement())
                break;

            xmlStreamReader.require(XMLStreamConstants.START_ELEMENT, null, ITEM);
            String itemID = nextValue(xmlStreamReader, ITEM_ID);
            xmlStreamReader.nextTag(); xmlStreamReader.require(XMLStreamConstants.START_ELEMENT, null, ITEM_DETAILS);
            String startTime = nextValue(xmlStreamReader, START_TIME);
            xmlStreamReader.nextTag();
            String averageTime = null;
            String averagePrice = null;

            if (xmlStreamReader.getLocalName().equals(AVERAGES))
            {
                averageTime = nextValue(xmlStreamReader, AVERAGE_TIME);
                averagePrice = nextValue(xmlStreamReader, AVERAGE_PRICE);
                xmlStreamReader.nextTag();
                xmlStreamReader.require(XMLStreamConstants.END_ELEMENT, null, AVERAGES);
                xmlStreamReader.nextTag();
            }
            String endTime = currentValue(xmlStreamReader, END_TIME);
            String url = nextValue(xmlStreamReader,ITEM_URL);
            xmlStreamReader.nextTag(); xmlStreamReader.require(XMLStreamConstants.END_ELEMENT, null, ITEM_DETAILS);
            xmlStreamReader.nextTag(); xmlStreamReader.require(XMLStreamConstants.END_ELEMENT, null, ITEM);

            writer.append(esc(itemID)).append(SEPARATOR)
                    .append(esc(startTime)).append(SEPARATOR)
                    .append(esc(endTime)).append(SEPARATOR)
                    .append(esc(url));
            if (averageTime!=null)
                writer.append(SEPARATOR).append(esc(averageTime)).append(SEPARATOR)
                        .append(esc(averagePrice));
            writer.println();                        
        }

        xmlStreamReader.require(XMLStreamConstants.END_ELEMENT, null, ROOT);
        writer.close();

    }

    private String esc(String string) {
        if (string.indexOf(',')!=-1)
            string = '"'+string+'"';
        return string;
    }

    private String nextValue(XMLStreamReader xmlStreamReader, String name) throws XMLStreamException {
        xmlStreamReader.nextTag();
        return currentValue(xmlStreamReader, name);
    }

    private String currentValue(XMLStreamReader xmlStreamReader, String name) throws XMLStreamException {
        xmlStreamReader.require(XMLStreamConstants.START_ELEMENT, null, name);
        String value = "";
        for (;;) {
            int next = xmlStreamReader.next();
            if (next==XMLStreamConstants.CDATA||next==XMLStreamConstants.SPACE||next==XMLStreamConstants.CHARACTERS)
                value += xmlStreamReader.getText();
            else if (next==XMLStreamConstants.END_ELEMENT)
                break;
            // ignore comments, PIs, attributes
        }
        xmlStreamReader.require(XMLStreamConstants.END_ELEMENT, null, name);
        return value.trim();
    }    
}