This PowerPoint is based on slides from:

Jason Hunter and Brett McLaughlin

Webprogramming (WEBP)2. Mar. 2010

By Henrik Høltzer

What is JDOM?JDOM is a way to represent an XML document

for easy and efficient reading, manipulation, and writingStraightforward APILightweight and fastJava-optimized

Despite the name similarity, it's not built on DOM or modeled after DOM

An open source project with an Apache-style license950 developers on jdom-interest (high traffic)800 lurkers on jdom-announce (low traffic)

The JDOM PhilosophyJDOM should be straightforward for Java

programmersUse the power of the language (Java 2)Take advantage of method overloading, the

Collections APIs, reflection, weak referencesProvide conveniences like type conversions

JDOM should hide the complexities of XML wherever possibleAn Element has text content, not a child Text

node with contentExceptions should contain useful error

messagesGive line numbers and specifics, use no SAX or

DOM specifics

More JDOM Philosophy JDOM should integrate with DOM and SAX

Reads and writes DOM docs and SAX eventsCan use any DOM or SAX parser (uses adapter model or

can use JAXP)

Why not use DOM:Same API on multiple languages, defined using IDLForeign to the Java environment, Java programmerFairly heavyweight in memory

Why not use SAX:No document modification, random access, or outputFairly steep learning curve to use correctly

JDOM is to DOM/SAX as RMI is to CORBAJava optimized, plays well with the other

The org.jdom.input PackageClasses for reading XML from existing

sources:DOMBuilderSAXBuilder

Also, outside contributions in jdom-contrib:ResultSetBuilderSpitfireBuilder

The org.jdom.output PackageClasses for writing XML to various forms of

output:DOMOutputterSAXOutputterXMLOutputter

Also, outside contributions in jdom-contrib:JTreeOutputter

General Program FlowNormally XML Document -> SAXBuilder -> XMLOutputter

DOM Node(s)

JDOM Document

SAXBuilder

DOMBuilder

XMLOutputter

SAXOutputter

DOMOutputter

XML Document

Direct Build

The Document lifecycleDocuments are rep. by the org.jdom.Document

classA lightweight object holding a DocType, ProcessingInstructions, a root Element (containing other Elements), and Comments

A document can be constructed from scratch:

Or it can be constructed from a file, stream, or URL:

Then it can be output as XML, or SAX, or DOM:

Document doc = new Document( new Element("root").setText("courseregister"));

SAXBuilder builder = new SAXBuilder(); Document doc = builder.build(url);

XMLOutputter outputter = new XMLOutputter(); outputter.output(doc, System.out);

Ensuring Well-FormednessThe Element constructor (and all other object

constructors) check to make sure the element is legali.e. the name and content don't contain

inappropriate characters

The add and remove methods also check document structureAn element may only exist at one point in the

treeOnly one value can be returned by getParent()

No loops in the graph are allowedExactly one root element must exist