In this tutorial we are going to see how you can parse an XML File using a SAX parser. SAX parsers are very popular and much more frequently used than DOM parsers. The reason is that they are much more memory efficient (and this is important for large XML Files) and much faster. It’s all down to the way the SAX parsers work. They don’t create an object with tree structure and store it in the memory while parsing the file. The idea of the SAX parsing is much simpler and it lies in callback methods. Basically there are 3 groups of callback methods:
startDocument()andendDocument(), called at the start and end of an XML document.startElement()andendElement()called at the start and end of an element tag.characters()called when the text contents between the start and end tags of an elements are parsed.
These are the functions that inform the clients about the structure of the XML File. In order to implement these functions you have to create a class that extends org.xml.sax.helpers.DefaultHandler class as you can see in the code snippets that follow.
Here is the XML File we are going to use for the demo:
testFile.xml:
<?xml version="1.0" encoding="UTF-8" standalone="no"?><company>
<employee id="10">
<firstname>Jeremy</firstname>
<lastname>Harley</lastname>
<email>james@example.org</email>
<department>Human Resources</department>
<salary>2000000</salary>
<address>34 Stanley St.</address>
</employee>
<employee id="2">
<firstname>John</firstname>
<lastname>May</lastname>
<email>john@example.org</email>
<department>Logistics</department>
<salary>400</salary>
<address>123 Stanley St.</address>
</employee>
</company>
Now we just have to create the MyHandler class that extends DefaultHandler and that will implement the callback functions we need.
MyHandler.java:
package com.javacodegeeks.java.core;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
public class MyHandler extends DefaultHandler {
boolean tagFname = false;
boolean tagLname = false;
boolean tagEmail = false;
boolean tagDep = false;
boolean tagSalary = false;
boolean tagAddress = false;
public void startElement(String uri, String localName, String qName,
Attributes attributes) throws SAXException {
if (attributes.getLength() > 0) {
String tag = "<" + qName;
for (int i = 0; i < attributes.getLength(); i++) {
tag += " " + attributes.getLocalName(i) + "="
+ attributes.getValue(i);
}
tag += ">";
System.out.println(tag);
} else {
System.out.println("<" + qName + ">");
}
if (qName.equalsIgnoreCase("firstname")) {
tagFname = true;
}
if (qName.equalsIgnoreCase("lastname")) {
tagLname = true;
}
if (qName.equalsIgnoreCase("email")) {
tagEmail = true;
}
if (qName.equalsIgnoreCase("department")) {
tagDep = true;
}
if (qName.equalsIgnoreCase("salary")) {
tagSalary = true;
}
if (qName.equalsIgnoreCase("address")) {
tagAddress = true;
}
}
public void characters(char ch[], int start, int length)
throws SAXException {
if (tagFname) {
System.out.println(new String(ch, start, length));
tagFname = false;
}
if (tagLname) {
System.out.println(new String(ch, start, length));
tagLname = false;
}
if (tagEmail) {
System.out.println(new String(ch, start, length));
tagEmail = false;
}
if (tagDep) {
System.out.println(new String(ch, start, length));
tagDep = false;
}
if (tagSalary) {
System.out.println(new String(ch, start, length));
tagSalary = false;
}
if (tagAddress) {
System.out.println(new String(ch, start, length));
tagAddress = false;
}
}
public void endElement(String uri, String localName, String qName)
throws SAXException {
System.out.println("</" + qName + ">");
}
}
ParseXMLFileWithSAX.java:
package com.javacodegeeks.java.core;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
public class ParseXMLFileWithSAX {
private static final String xmlFilePath = "C:\\Users\\nikos7\\Desktop\\filesForExamples\\testFile.xml";
public static void main(String argv[]) {
try {
SAXParserFactory factory = SAXParserFactory.newInstance();
SAXParser saxParser = factory.newSAXParser();
saxParser.parse(xmlFilePath, new MyHandler());
} catch (Exception e) {
e.printStackTrace();
}
}
}
Output:
<company>
<employee id=10>
<firstname>
Jeremy
</firstname>
<lastname>
Harley
</lastname>
<email>
james@example.org
</email>
<department>
Human Resources
</department>
<salary>
2000000
</salary>
<address>
34 Stanley St.
</address>
</employee>
<employee id=2>
<firstname>
John
</firstname>
<lastname>
May
</lastname>
<email>
john@example.org
</email>
<department>
Logistics
</department>
<salary>
400
</salary>
<address>
123 Stanley St.
</address>
</employee>
</company>
This was an example on how to read XML File in Java using SAX parser example
