Skipping nodes with sax

Question

Is it possible to skip nodes when parsing and how, does this skippedEntity have anything to do with it?

Consider this XML :

<?xml version="1.0"?>

<nutrition>

<daily-values>
    <total-fat units="g">65</total-fat>
    <saturated-fat units="g">20</saturated-fat>
    <cholesterol units="mg">300</cholesterol>
    <sodium units="mg">2400</sodium>
    <carb units="g">300</carb>
    <fiber units="g">25</fiber>
    <protein units="g">50</protein>
</daily-values>

</nutrition>

I want to skip "sodium" element

Answer 1

Please edit your post to include a sample XML and a description of what you mean by "skip nodes".

Since your parser gets control on each event, you can choose to do nothing based on any criteria you desire. If you want to skip an entire subtree, you have to set a global flag when you encounter the subtree's start element and clear the flag at the end element; then use the flag to control processing of the contained nodes.

Answer 2

You need to handle that yourself in your handler. Ignore the elements that you don't want by not assigning the corresponding characters to your bean property.

skippedEntity() method will not help with this.

Answer 3

You could do something like the following:

import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.XMLReader;

public class Demo {

    public static void main(String[] args) throws Exception {
        SAXParserFactory spf = SAXParserFactory.newInstance();
        SAXParser sp = spf.newSAXParser();
        XMLReader xr = sp.getXMLReader();
        xr.setContentHandler(new MyContentHandler(xr));
        xr.parse("input.xml");
    }
}

MyContentHandler

This class is responsible for processing your XML document. When you hit a node you want to ignore you can swap in the IgnoringContentHandler which will swallow all events for that node.

import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;

public class MyContentHandler implements ContentHandler {

    private XMLReader xmlReader;

    public MyContentHandler(XMLReader xmlReader) {
        this.xmlReader = xmlReader;
    }

    public void setDocumentLocator(Locator locator) {
    }

    public void startDocument() throws SAXException {
    }

    public void endDocument() throws SAXException {
    }

    public void startPrefixMapping(String prefix, String uri)
            throws SAXException {
    }

    public void endPrefixMapping(String prefix) throws SAXException {
    }

    public void startElement(String uri, String localName, String qName,
            Attributes atts) throws SAXException {
        if("sodium".equals(qName)) {
            xmlReader.setContentHandler(new IgnoringContentHandler(xmlReader, this));
        } else {
            System.out.println("START " + qName);
        }
    }

    public void endElement(String uri, String localName, String qName)
            throws SAXException {
        System.out.println("END " + qName);
    }

    public void characters(char[] ch, int start, int length)
            throws SAXException {
        System.out.println(new String(ch, start, length));
    }

    public void ignorableWhitespace(char[] ch, int start, int length)
            throws SAXException {
    }

    public void processingInstruction(String target, String data)
            throws SAXException {
    }

    public void skippedEntity(String name) throws SAXException {
    }

}

IgnoringContentHandler

When the IgnoringContentHandler is done swallowing events it passes control back to your main ContentHandler.

import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;

public class IgnoringContentHandler implements ContentHandler {

    private int depth = 1;
    private XMLReader xmlReader;
    private ContentHandler contentHandler;

    public IgnoringContentHandler(XMLReader xmlReader, ContentHandler contentHandler) {
        this.contentHandler = contentHandler;
        this.xmlReader = xmlReader;
    }

    public void setDocumentLocator(Locator locator) {
    }

    public void startDocument() throws SAXException {
    }

    public void endDocument() throws SAXException {
    }

    public void startPrefixMapping(String prefix, String uri)
            throws SAXException {
    }

    public void endPrefixMapping(String prefix) throws SAXException {
    }

    public void startElement(String uri, String localName, String qName,
            Attributes atts) throws SAXException {
        depth++;
    }

    public void endElement(String uri, String localName, String qName)
            throws SAXException {
        depth--;
        if(0 == depth) {
           xmlReader.setContentHandler(contentHandler);
        }
    }

    public void characters(char[] ch, int start, int length)
            throws SAXException {
    }

    public void ignorableWhitespace(char[] ch, int start, int length)
            throws SAXException {
    }

    public void processingInstruction(String target, String data)
            throws SAXException {
    }

    public void skippedEntity(String name) throws SAXException {
    }

}