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:
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 | <?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:
001 002 003 004 005 006 007 008 009 010 011 012 013 014 015 016 017 018 019 020 021 022 023 024 025 026 027 028 029 030 031 032 033 034 035 036 037 038 039 040 041 042 043 044 045 046 047 048 049 050 051 052 053 054 055 056 057 058 059 060 061 062 063 064 065 066 067 068 069 070 071 072 073 074 075 076 077 078 079 080 081 082 083 084 085 086 087 088 089 090 091 092 093 094 095 096 097 098 099 100 101 102 103 104 | 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:
01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | 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
