Easy Java/XML integration with JDOM, Part 1

Learn about a new open source API for working with XML

By Jason Hunter and Brett Mclaughlin, JavaWorld.com, 05/18/00

TEXTBOX: TEXTBOX_HEAD: Easy Java/XML integration with JDOM: Read the whole series!

• Part 1. Learn about a new API for working with XML
• Part 2. Use JDOM to create and mutate XML

JDOM interoperates well with existing standards such as the Simple API for XML (SAX) and the Document Object Model (DOM). However, it's more than a simple abstraction above those APIs. JDOM takes the best concepts from existing APIs and creates a new set of classes and interfaces that provide, in the words of one JDOM user, "the interface I expected when I first looked at org.w3c.dom." JDOM can read from existing DOM and SAX sources, and can output to DOM- and SAX-receiving components. That ability enables JDOM to interoperate seamlessly with existing program components built against SAX or DOM.

JDOM has been made available under an Apache-style, open source license. That license is among the least restrictive software licenses available, enabling developers to use JDOM in creating products without requiring them to release their own products as open source. It is the license model used by the Apache Project, which created the Apache server. In addition to making the software free, being open source enables the API to take contributions from some of the best Java and XML minds in the industry and to adapt quickly to new standards as they evolve.

The JDOM philosophy

First and foremost, the JDOM API has been developed to be straightforward for Java programmers. While other XML APIs were created to be cross-language (supporting the same API for Java, C++, and even JavaScript), JDOM takes advantage of Java's abilities by using features such as method overloading, the Collections APIs, and (behind the scenes) reflection.

To be straightforward, the API has to represent the document in a way programmers would expect. For example, how would a Java programmer expect to get the text content of an element?

<element>This is my text content</element>

In some APIs, an element's text content is available only as a child Node of the Element. While technically correct, that design requires the following code to access an element's content:

String content = element.getFirstChild()
                    .getValue();

However, JDOM makes the text content available in a more straightforward way:

String text = element.getText();

Wherever possible, JDOM makes the programmer's job easier. The rule of thumb is that JDOM should help solve 80 percent or more of Java/XML problems with 20 percent or less of the traditional effort. That does not mean that JDOM conforms to only 80 percent of the XML specification. (In fact, we expect that JDOM will be fully compliant before the 1.0 final release.) What that rule of thumb does mean is that just because something could be added to the API doesn't mean it will. The API should remain sleek.