How to get a specific event/attribute content from an xml string via stAX or SAX

Question

I have a xml POST response which I receive as a string. I need the content of the particular "pnr" (see in xml) to pass it on to another GET request. I am trying sax and stAX to achieve this but failing miserably. I used getElementsByTagName and also getAttribute, but no go... Here's my code and later the xml string that I receive.

Any kind of help will be a gift

package rest;
import javax.xml.parsers.*;
import org.xml.sax.InputSource;
import org.w3c.dom.*;
import java.io.*;


public class ParseXMLString {

  public static void main(String arg[]) {
    String outputString =  RESTClient.postConfirm(); // this is the xml string response I am getting

    try {
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        DocumentBuilder db = dbf.newDocumentBuilder();
        InputSource is = new InputSource();
        is.setCharacterStream(new StringReader(outputString));

        Document doc = db.parse(is);
        String Parentnode = doc.getDocumentElement().getAttribute("pnr");       
//           Element element = (Element) Parentnode.;
//           NodeList name = element.getElementsByTagName("pnr");
//           Element line = (Element) name.item(0);
           //String IDList = getCharacterDataFromElement(line);   
           System.out.println(Parentnode);
    }
    catch (Exception e) {
        e.printStackTrace();
    }
  }

  public static String getCharacterDataFromElement(Element e) {
    Node child = e.getFirstChild();
    if (child instanceof CharacterData) {
       CharacterData cd = (CharacterData) child;
       return cd.getData();
    }
    return "?";
  }
}

And here is the the XML String I have received:

<?xml version="1.0" encoding="UTF-8"?><Ticket><bookedSeats>3</bookedSeats><bpAddress>Anand Rao Circle</bpAddress><bpLandMark>ganesha temple</bpLandMark><bpLocation> Ghousia College</bpLocation><bpPhoneNo>98798679769</bpPhoneNo><bpTime>1200</bpTime><busServiceName>efdf</busServiceName><busType>Volvo A/C Semi Sleeper (2+2)</busType><commission>66.19</commission><dateOfJourney>2012-10-05</dateOfJourney><destination>Chennai</destination><fare>600.0</fare><issueTime>2012-10-04T15:46:45.073+05:30</issueTime><noOfSeats>1</noOfSeats><passengerMobile>1234567890</passengerMobile><passengerName>Test</passengerName><pnr>RATPKES44974756</pnr><seatDetails><seatDetail><commission>66.19</commission><fare>600.0</fare><gender>MALE</gender><passengerAge>0</passengerAge><passengerMobile>1234567890</passengerMobile><passengerName>Test</passengerName><prime>false</prime><seatName>3</seatName></seatDetail></seatDetails><source>Bangalore</source><status>BOOKED</status><travelsName>Rajratan Travels</travelsName></Ticket>

Answer 1

this bit of code will get you the pnr :

                 NodeList nodeLst = doc.getElementsByTagName("Ticket");
                 Node ticket = nodeLst.item(0);
                 NodeList attr = ticket.getChildNodes();
                 for (int i = 0; i < attr.getLength(); i++){
                     if (attr.item(i).getNodeName().equals("pnr"))
                         System.out.println(attr.item(i).getTextContent());
                 }

Answer 2

If I were to solve this problem, I'd probably use XPath. But since you specifically asked for StAX, here's an example parser (note that this is just skeleton code to get you started).

import java.io.StringReader;
import java.util.Iterator;
import javax.xml.stream.XMLEventReader;
import javax.xml.stream.XMLInputFactory;
import javax.xml.stream.XMLStreamException;
import javax.xml.stream.XMLStreamReader;
import javax.xml.stream.events.Attribute;
import javax.xml.stream.events.Characters;
import javax.xml.stream.events.EndElement;
import javax.xml.stream.events.StartElement;
import javax.xml.stream.events.XMLEvent;

public class ParseXMLStringStAX {

    private static final String PNR = "pnr";

    private String characters;

    public String parse(String xmlString) throws XMLStreamException, Exception {
        XMLEventReader reader = null;
        try {
            if (xmlString == null || xmlString.isEmpty()) {
                throw new IllegalArgumentException("Illegal initializiation (xmlString is null or empty)");
            }
            StringReader stringReader = new StringReader(xmlString);
            XMLInputFactory inputFact = XMLInputFactory.newInstance();
            XMLStreamReader streamReader = inputFact.createXMLStreamReader(stringReader);
            reader = inputFact.createXMLEventReader(streamReader);

            while (reader.hasNext()) {
                XMLEvent event = reader.nextEvent();

                if (event.isCharacters()) {
                    characters(event);
                }
                if (event.isStartElement()) {
                    startElement(event);
                    // handle attributes
                    Iterator<Attribute> attributes = event.asStartElement().getAttributes();
                    while(attributes.hasNext()) {
                        attribute(attributes.next());
                    }
                }
                if (event.isEndElement()) {
                    // found what we want?
                    if (endElement(event)) {
                        endDocument(null);
                        break;
                    }
                }
                if (event.isStartDocument()) {
                    startDocument(event);
                }
                if (event.isEndDocument()) {
                    endDocument(event);
                }

            }
        } catch (XMLStreamException ex) {
            throw ex;
        } finally {
            try {
                if (reader != null) {
                    reader.close();
                }
            } catch (XMLStreamException ex) {
            }
        }
        return characters;
    }

    private void attribute(XMLEvent event) throws Exception {

    }

    private void characters(XMLEvent event) throws Exception {
        Characters asCharacters = event.asCharacters();
        if (asCharacters.isWhiteSpace())
            return;
        if (characters == null) {
            characters = asCharacters.getData();
        } else {
            characters += asCharacters.getData();
        }
    }

    private void startElement(XMLEvent event) throws Exception {
        StartElement startElement = event.asStartElement();
        String name = startElement.getName().getLocalPart();
        characters = null;
    }

    private boolean endElement(XMLEvent event) throws Exception {
        EndElement endElement = event.asEndElement();
        String name = endElement.getName().getLocalPart();
        if (PNR.equals(name)) {
            return true;
        }
        return false;
    }

    private void startDocument(XMLEvent event) {
        System.out.println("Parsing started");
    }

    private void endDocument(XMLEvent event) {
        System.out.println("Parsing ended");
    }

    public static void main(String[] argv) throws XMLStreamException, Exception {
        String xml = "";

        xml += "<Ticket>";
        xml += "    <bookedSeats>3</bookedSeats>";
        xml += "    <bpAddress>Anand Rao Circle</bpAddress>";
        xml += "    <bpLandMark>ganesha temple</bpLandMark>";
        xml += "    <bpLocation> Ghousia College</bpLocation>";
        xml += "    <bpPhoneNo>98798679769</bpPhoneNo>";
        xml += "    <bpTime>1200</bpTime>";
        xml += "    <busServiceName>efdf</busServiceName>";
        xml += "    <busType>Volvo A/C Semi Sleeper (2+2)</busType>";
        xml += "    <commission>66.19</commission>";
        xml += "    <dateOfJourney>2012-10-05</dateOfJourney>";
        xml += "    <destination>Chennai</destination>";
        xml += "    <fare>600.0</fare>";
        xml += "    <issueTime>2012-10-04T15:46:45.073+05:30</issueTime>";
        xml += "    <noOfSeats>1</noOfSeats>";
        xml += "    <passengerMobile>1234567890</passengerMobile>";
        xml += "    <passengerName>Test</passengerName>";
        xml += "    <pnr>RATPKES44974756</pnr>";
        xml += "    <seatDetails>";
        xml += "        <seatDetail>";
        xml += "            <commission>66.19</commission>";
        xml += "            <fare>600.0</fare>";
        xml += "            <gender>MALE</gender>";
        xml += "            <passengerAge>0</passengerAge>";
        xml += "            <passengerMobile>1234567890</passengerMobile>";
        xml += "            <passengerName>Test</passengerName>";
        xml += "            <prime>false</prime>";
        xml += "            <seatName>3</seatName>";
        xml += "        </seatDetail>";
        xml += "    </seatDetails>";
        xml += "    <source>Bangalore</source>";
        xml += "    <status>BOOKED</status>";
        xml += "    <travelsName>Rajratan Travels</travelsName>";
        xml += "</Ticket>";

        ParseXMLStringStAX parser = new ParseXMLStringStAX();
        String pnr = parser.parse(xml);
        System.out.println("--> Result: " + String.valueOf(pnr));
    }
}

Answer 3

Instead of SAX or StAX you could do the following with the javax.xml.xpath APIs in the JDK/JRE since Java SE 5:

Demo

import java.io.StringReader;
import javax.xml.xpath.*;
import org.xml.sax.InputSource;

public class Demo {

    public static void main(String[] args) throws Exception {
        String xml = "<?xml version='1.0' encoding='UTF-8'?><Ticket><bookedSeats>3</bookedSeats><bpAddress>Anand Rao Circle</bpAddress><bpLandMark>ganesha temple</bpLandMark><bpLocation> Ghousia College</bpLocation><bpPhoneNo>98798679769</bpPhoneNo><bpTime>1200</bpTime><busServiceName>efdf</busServiceName><busType>Volvo A/C Semi Sleeper (2+2)</busType><commission>66.19</commission><dateOfJourney>2012-10-05</dateOfJourney><destination>Chennai</destination><fare>600.0</fare><issueTime>2012-10-04T15:46:45.073+05:30</issueTime><noOfSeats>1</noOfSeats><passengerMobile>1234567890</passengerMobile><passengerName>Test</passengerName><pnr>RATPKES44974756</pnr><seatDetails><seatDetail><commission>66.19</commission><fare>600.0</fare><gender>MALE</gender><passengerAge>0</passengerAge><passengerMobile>1234567890</passengerMobile><passengerName>Test</passengerName><prime>false</prime><seatName>3</seatName></seatDetail></seatDetails><source>Bangalore</source><status>BOOKED</status><travelsName>Rajratan Travels</travelsName></Ticket>";

        XPathFactory xpf = XPathFactory.newInstance();
        XPath xpath = xpf.newXPath();

        InputSource inputSource = new InputSource(new StringReader(xml));
        String pnr = (String) xpath.evaluate("/Ticket/pnr", inputSource, XPathConstants.STRING);
        System.out.println(pnr);
    }

}

Output

RATPKES44974756