Tutorials : Digesting XML documents :

The first simple example

We'll start with a very simple XML example that, nevertheless, covers most document types: a list of DVDs:

<?xml version="1.0" encoding="UTF-8"?>
<collection>
  <dvd id="A">
    <title>Lord of the Rings: The Fellowship of the Ring</title>
    <length>178</length>
    <actor>Ian Holm</actor>
    <actor>Elijah Wood</actor>
    <actor>Ian McKellen</actor>
  </dvd>
  <dvd id="B">
    <title>The Matrix</title>
    <length>136</length>
    <actor>Keanu Reeves</actor>
    <actor>Laurence Fishburne</actor>
  </dvd>
  <dvd id="C">
    <title>Amadeus</title>
    <length>158</length>
    <actor>F. Murray Abraham</actor>
    <actor>Tom Hulce</actor>
    <actor>Elizabeth Berridge</actor>
  </dvd>
</collection>

It contains most of the ordinary XML constructions:

• an attribute: "id"
• text contents: "title", "length", "actor"
• repeated elements: "dvd" is complex (a Java bean type) and a simple "actor" (a Java String)
• an integer value: "length"--the rest are Strings

The example will therefore be helpful even when we start parsing more complex XML files.

Following the rules above we first decide to extract all data from the document. To hold the data we chose to use two classes: A "wrapper" class called DVDCollection, which holds the DVDs, and a DVD class that holds information for one DVD. They're both beans with a few extra methods added:

Listing 2: The DVDCollection class

package dk.hansen;

import java.util.*;

public class DVDCollection {

  private ArrayList DVDs = new ArrayList();

  public ArrayList getDVDs() {
    return DVDs;
  }

  public void setDVDs(ArrayList dvds) {
    this.DVDs = dvds;
  }

  public void addDVD(DVD dvd) {
    DVDs.add(dvd);
  }

}

You'll see below how Digester is using the addDVD method.

Listing 3: The DVD class

package dk.hansen;

import java.util.*;

public class DVD {

  private String id = "";
  private String title = "";
  private int length = 0;
  private ArrayList actors = new ArrayList();

  public void addActor(String actor) {
    actors.add(actor);
  }

  public ArrayList getActors() {
    return actors;
  }

  public void setActors(ArrayList actors) {
    this.actors = actors;
  }

  public String getId() {
    return id;
  }

  public void setId(String id) {
    this.id = id;
  }

. . . (remaining getters and setters)

}

The addActor method is also used by Digester.

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