Parser to parse unknown XML Schema in java

Question

I tried understanding all other answers in stackoverflow.But I am not able to relate those answers to my question.

When I call a web service, I get response. I get schema by response.getData();(The XML of the data table containing the results.) (return type String). We don't know what data we get in that XML.

I need to use a 3rd party parser, so that when I give the above string to one method in that parser it should return all the elements in that XML and then I can print the required elements.

I don't want to start parsing the XML myself. Is there a way I can do this? (Does it even make any sense?). Sorry If I am totally wrong. (using Axis2/eclipse) (Edited)

Edit: Adding the code I've tried already.

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
NodeList nodeList = null;


        try {
            String xml = res2.getResult().getRawData();
            DocumentBuilder db = dbf.newDocumentBuilder();
            Document document = db.parse(new ByteArrayInputStream(xml.getBytes()));
            nodeList = document.getElementsByTagName("PhoneNumber");
            NamedNodeMap attrib = document.getAttributes();
            for (int i = 0; i < attrib.getLength(); i++) {
                String nodeName = attrib.item(i).getNodeName();
                //nodeName
                String nodeValue = attrib.item(i).getNodeValue();
            }

But I am not sure if the PhoneNumber is with that tag or other name. Also we don't know how many tags we have.

Thanks, Using the code by SyamS, I am able to print all the nodes and corresponding values from xml. Now I want to store that into a hashmap with key as node name and node values in a list.

Example XML :

<Docs>
<Doc>
<Id>12</Id>
<Phone>1234</Phone>
</Doc>
<Doc>
<Id>147</Id>
<Phone>12345</Phone>
<Locked>false</Locked>
<BID>2</BID>
<DocId>8</DocId>
<Date>2014-02-04T12:18:50.063-07:00</Date>
<Urgent>false</Urgent>
</Doc>
</Docs>

Answer 1

You need not go for a third party library for this. you could simply identify all leaf nodes using xpath and read the value (as well as attributes). For example

public static Map<String, List<String>> parseXml(String xml) throws XMLStreamException {
    StringBuilder content = null;
    Map<String, List<String>> dataMap = new HashMap<>();
    XMLInputFactory factory = XMLInputFactory.newInstance();
    InputStream stream = new ByteArrayInputStream(xml.getBytes());
    XMLStreamReader reader = factory.createXMLStreamReader(stream);

    while (reader.hasNext()) {
        int event = reader.next();

        switch (event) {
            case XMLStreamConstants.START_ELEMENT:
                content = new StringBuilder();
                break;

            case XMLStreamConstants.CHARACTERS:
                if (content != null) {
                    content.append(reader.getText().trim());
                }
                break;

            case XMLStreamConstants.END_ELEMENT:
                if (content != null) {
                    String leafText = content.toString();
                    if(dataMap.get(reader.getLocalName()) == null){
                        List<String> values = new ArrayList<>();
                        values.add(leafText);
                        dataMap.put(reader.getLocalName(), values);
                    } else {
                        dataMap.get(reader.getLocalName()).add(leafText);
                    }
                }
                content = null;
                break;

            case XMLStreamConstants.START_DOCUMENT:
                break;
        }

    }

    return dataMap;
}

Answer 2

You should read answers related to Best XML parser for Java. Using the example XML from Sample XML File (books.xml) which I've downloaded to a temp folder on my C: drive, you might use Java's native SAXParser library. Here's an example class you might use to iterate through all the elements in XML. Create the class in your project, and call its parse method as:

File xml = new File("c:/temp/books.xml");
MySaxParser sax = new MySaxParser(xml);
sax.parseXml();

This is the class you can copy into your project to try it out. Modify according to your needs, of course. The imports should direct you to the appropriate Java API pages such as Class SAXParser to begin with.

import java.io.File;
import java.io.IOException;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

public class MySaxParser extends DefaultHandler {
    private String absolutePathToXml = "";
    public MySaxParser(File xml) {
        absolutePathToXml = xml.getAbsolutePath();
    }
    /**
     * Parses an XML file into memory
     */
    public void parseXml() {
        SAXParserFactory factory = SAXParserFactory.newInstance();
        try {
            SAXParser parser = factory.newSAXParser();
            parser.parse(absolutePathToXml, this);
        } catch (ParserConfigurationException e) {
            System.out.println("ParserConfigurationException: ");
            e.printStackTrace();
        } catch (SAXException e) {
            System.out.println("SAXException: ");
            e.printStackTrace();
        } catch (IOException e) {
            System.out.println("IOException: ");
            e.printStackTrace();
        }
    }
    /**
     * Event: Parser starts reading an element
     */
    @Override
    public void startElement(String s1, String s2, String elementName, Attributes attributes) 
            throws SAXException {
        //print an element's name
        System.out.println("element: " + elementName);
        //print all attributes for this element
        for(int i = 0; i < attributes.getLength(); i++) {
            System.out.println("attribute: " + attributes.getValue(i));
        }
    }
}