XML Tutorial · XML in Code · Lesson 19 of 28

XML in Java

Java's built-in XML APIs: DOM, SAX, StAX and the Transformer, plus secure parser settings and JAXB-style data binding.

Create a free account to save this page, take notes and track your progress. Sign in

The JAXP family

API	Style	Use for
DOM (`DocumentBuilder`)	Whole tree in memory	Small and medium documents you edit or query
SAX (`SAXParser`)	Push: callbacks per event	Large documents, read once
StAX (`XMLStreamReader` / `Writer`)	Pull: you ask for the next event	Large documents, simpler than SAX
XPath (`javax.xml.xpath`)	Queries over a DOM	Selecting nodes
Transformer (`javax.xml.transform`)	XSLT 1.0, serialising	Transforming and writing XML
Validation (`javax.xml.validation`)	XSD 1.0	Checking documents

Jakarta XML Binding (JAXB, formerly built into Java 8) and Jackson XML map XML to Java objects with annotations; both are separate libraries today.

Java examples aren't runnable in the browser; the output shown is from a real JDK 21 run.

SAX: events as the parser reads

SAX handler

import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.helpers.DefaultHandler;
import java.io.ByteArrayInputStream;

public class Main {
    public static void main(String[] args) throws Exception {
        String xml = """
                <shop>
                  <product sku="TEA-01" category="drinks"><name>Green tea</name><price>3.50</price><stock>40</stock></product>
                  <product sku="COF-02" category="drinks"><name>Coffee beans</name><price>9.90</price><stock>0</stock></product>
                  <product sku="MUG-07" category="kitchen"><name>Camel mug</name><price>12.00</price><stock>15</stock></product>
                  <product sku="PAN-03" category="kitchen"><name>Frying pan</name><price>29.00</price><stock>4</stock></product>
                </shop>""";
        var handler = new DefaultHandler() {
            String current = "";
            double total = 0;
            StringBuilder text = new StringBuilder();

            @Override public void startElement(String uri, String local, String qName, Attributes atts) {
                if (qName.equals("product")) current = atts.getValue("sku");
                text.setLength(0);
            }
            @Override public void characters(char[] ch, int start, int length) { text.append(ch, start, length); }
            @Override public void endElement(String uri, String local, String qName) {
                if (qName.equals("price")) {
                    total += Double.parseDouble(text.toString());
                    System.out.println(current + " costs " + text);
                }
            }
            @Override public void endDocument() { System.out.println("total: " + total); }
        };
        SAXParserFactory.newInstance().newSAXParser().parse(new ByteArrayInputStream(xml.getBytes("UTF-8")), handler);
    }
}

import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.helpers.DefaultHandler;
import java.io.ByteArrayInputStream;

@Override public void startElement(String uri, String local, String qName, Attributes atts) {
                if (qName.equals("product")) current = atts.getValue("sku");
                text.setLength(0);
            }
            @Override public void characters(char[] ch, int start, int length) { text.append(ch, start, length); }
            @Override public void endElement(String uri, String local, String qName) {
                if (qName.equals("price")) {
                    total += Double.parseDouble(text.toString());
                    System.out.println(current + " costs " + text);
                }
            }
            @Override public void endDocument() { System.out.println("total: " + total); }
        };
        SAXParserFactory.newInstance().newSAXParser().parse(new ByteArrayInputStream(xml.getBytes("UTF-8")), handler);
    }
}

Output

TEA-01 costs 3.50
COF-02 costs 9.90
MUG-07 costs 12.00
PAN-03 costs 29.00
total: 54.4

Run this on your computer — see “Get Started” for setup.

StAX: pull parsing and writing

StAX reader and writer

import javax.xml.stream.*;
import java.io.*;

public class Main {
    public static void main(String[] args) throws Exception {
        String xml = """
                <shop>
                  <product sku="TEA-01" category="drinks"><name>Green tea</name><price>3.50</price><stock>40</stock></product>
                  <product sku="COF-02" category="drinks"><name>Coffee beans</name><price>9.90</price><stock>0</stock></product>
                  <product sku="MUG-07" category="kitchen"><name>Camel mug</name><price>12.00</price><stock>15</stock></product>
                  <product sku="PAN-03" category="kitchen"><name>Frying pan</name><price>29.00</price><stock>4</stock></product>
                </shop>""";
        XMLStreamReader r = XMLInputFactory.newInstance().createXMLStreamReader(new StringReader(xml));
        StringWriter out = new StringWriter();
        XMLStreamWriter w = XMLOutputFactory.newInstance().createXMLStreamWriter(out);
        w.writeStartElement("restock");
        String sku = null;
        while (r.hasNext()) {
            if (r.next() == XMLStreamConstants.START_ELEMENT) {
                if (r.getLocalName().equals("product")) sku = r.getAttributeValue(null, "sku");
                if (r.getLocalName().equals("stock") && Integer.parseInt(r.getElementText()) < 5) {
                    w.writeEmptyElement("item");
                    w.writeAttribute("sku", sku);
                }
            }
        }
        w.writeEndElement();
        w.close();
        System.out.println(out);
    }
}

import javax.xml.stream.*;
import java.io.*;

public class Main {
    public static void main(String[] args) throws Exception {
        String xml = """
                <shop>
                  <product sku="TEA-01" category="drinks"><name>Green tea</name><price>3.50</price><stock>40</stock></product>
                  <product sku="COF-02" category="drinks"><name>Coffee beans</name><price>9.90</price><stock>0</stock></product>
                  <product sku="MUG-07" category="kitchen"><name>Camel mug</name><price>12.00</price><stock>15</stock></product>
                  <product sku="PAN-03" category="kitchen"><name>Frying pan</name><price>29.00</price><stock>4</stock></product>
                </shop>""";
        XMLStreamReader r = XMLInputFactory.newInstance().createXMLStreamReader(new StringReader(xml));
        StringWriter out = new StringWriter();
        XMLStreamWriter w = XMLOutputFactory.newInstance().createXMLStreamWriter(out);
        w.writeStartElement("restock");
        String sku = null;
        while (r.hasNext()) {
            if (r.next() == XMLStreamConstants.START_ELEMENT) {
                if (r.getLocalName().equals("product")) sku = r.getAttributeValue(null, "sku");
                if (r.getLocalName().equals("stock") && Integer.parseInt(r.getElementText()) < 5) {
                    w.writeEmptyElement("item");
                    w.writeAttribute("sku", sku);
                }
            }
        }
        w.writeEndElement();
        w.close();
        System.out.println(out);
    }
}

Output

<restock><item sku="COF-02"/><item sku="PAN-03"/></restock>

Run this on your computer — see “Get Started” for setup.

Java's DocumentBuilderFactory resolves external entities by default. Always configure it securely for untrusted input; see XML security.

Test yourself

Which Java XML API lets your code ask for the next event, rather than receiving callbacks?

StAX
SAX
DOM
JAXB

Show answer

Answer: StAX

StAX is a pull parser; SAX pushes events to a handler.