Tuesday, February 22, 2011

Hello World with Apache Commons Digester

This example will shows how to get started with Apache Commons Digester.

What is Apache Commons Digester?

Simply, you can use this to read a XML file against a particular pattern (say, particular tag in XML file) and if it found, you can trigger some actions (say, a method, so that method will be called if that pattern is matched)

So Let's start then,

You shoud have JDK 1.5 installed and need to download several libraries, which are,

1. Apache Commons Digester Library.
2. Apache Commons Logging.
3. Apache Commons BeanUtils.

I'm using eclipse as the IDE, so here we go,

Create a Java project from eclipse and add those downloaded libraries to that and set the build path correctly.
Create a XML file with following contents,


Create a Java class with a main method, Let's call this as DigesterTest.java

add following method there,
     * Action method. This will be called if there any matched content.
     * @param vendor
     *            Value of the tag "vendor".
     * @param model
     *            Value of the tag "model".
     * @param enginecapacity
     *            Value of the tag "enginecapacity".
     * @param enginetype
     *            Value of the tag "enginetype".
     * @param doors
     *            Value of the tag "doors".
     * @param color
     *            Value of the tag "color".
    public void getVehicleInfo(String vendor, String model,
        String enginecapacity, String enginetype, String doors,
        String color) {
    System.out.println("Vendor : " + vendor);
    System.out.println("Model : " + model);
    System.out.println("Engine Capacity : " + enginecapacity);
    System.out.println("Engine Type : " + enginetype);
    System.out.println("Doors: " + doors);
    System.out.println("Color : " + color);

     * Creates certain patterns to check against with XML file, if there a
     * match, action method will be called.
     * @throws SAXException
     * @throws IOException
    public void run() throws IOException, SAXException {

    Digester digester = new Digester();
    digester.push(new DigesterTest());

    digester.addCallMethod("vehicles/suv", "getVehicleInfo", 6);
    digester.addCallParam("vehicles/suv/vendor", 0);
    digester.addCallParam("vehicles/suv/model", 1);
    digester.addCallParam("vehicles/suv/enginecapacity", 2);
    digester.addCallParam("vehicles/suv/enginetype", 3);
    digester.addCallParam("vehicles/suv/doors", 4);
    digester.addCallParam("vehicles/suv/color", 5);

    InputStream inputStream = DigesterTest.class.getClassLoader()


     * Main method.
     * @param args
     * @throws IOException
     * @throws SAXException
    public static void main(String[] args) throws IOException, SAXException {
    DigesterTest digesterTest = new DigesterTest();


Here is the directory structure of my eclipse project,

Right click on DigesterTest.java and point to Run as >  Java Application.