The Java™ Platform and XML

The Java™ Platform and XML Portable Code, Portable Data James Duncan Davidson Staff Engineer, Sun Microsystems, Inc.

Our Overall Goals • Adopt existing open standards allowing the use of XML by Java™ developers • Participate in the various XML groups such as W3C and OASIS • Integrate XML technologies into the Core Platform as appropriate

Our Activities • W3C Participation • XML Working Group • DOM Working Group • XSL Working Group • Developing APIs • JAXP • Data Bindings • Experimenting / Implementing • Project X

Java API for XML Parsers (JAXP) • A thin and lightweight API for parsing XML documents • Allows for pluggable parsers • Allows processing of XML documents using the predominant methods: • Callback Driving (SAX) • Tree Based (DOM)

JAXP Illustration User Application JAXP Reference Other Parser Parser Java Runtime

SAX 1.0 • Simple API for XML • Accesses Document Serially • Fast and Lightweight • Harder to Program • Sequential Access Only • API in packages org.xml.sax.*

SAX in Action

Using SAX via JAXP import java.xml.parsers.*;import org.xml.sax.*;String uri = “http://server/resource.xml”;SAXParserFactory spf;SAXParser parser;HandlerBase handler;spf = SAXParserFactory.newInstance();spf.setValidating(true);parser = spf.newSAXParser();parser.parse(uri, handler);// can also parse InputStreams, Files, and SAX// input sources

DOM Level 1 • Document Object Model • Access XML Documents via a tree structure • Composed of element nodes and text nodes • Can “walk” the tree back and forth • Larger memory requirements • Package: org.w3c.dom.*

DOM in Action

Using DOM with JAXP import java.xml.parsers.*;import org.w3c.dom.*;String uri = “http://server/resource.xml”;DocumentBuilderFactory dbf;DocumentBuilder builder;Document document;dbf = DocumentBuilderFactory.newInstance();dbf.setValidating(true);builder = dbf.newDocmentBuilder();document = builder.parse(uri);// can also parse InputStreams, Files, and SAX// input sources

Namespaces • Defines a distinct set of XML markup elements • Associates a URI with a prefix • Allows multiple vocabularies to be combined in a single XML document

Namespace Example <?xml version=“1.0”?><book xmlns=“http://server/book” xmlns:isbn=“http://other.gov/isbn”> <title>Cheaper by the Dozen</title> <isbn:number>1568491379</isbn:number></book>

Namespaces in JAXP // SAX Casespf = SAXParserFactory.newInstance();spf.setValidating(true);spf.setNamespaceAware(true);parser = spf.newSAXParser();parser.parse(uri, handler);// DOM Casedbf = DocumentBuilderFactory.newInstance();dbf.setValidating(true);dbf.setNamespaceAware(true);builder = dbf.newDocmentBuilder();document = builder.parse(uri);

Using a Compliant Parser • Factories are looked up using System properties • javax.xml.parsers.SAXParserFactory • javax.xml.parsers.DocumentBuilderFactory • Change the property and you can use any parser

JAXP Schedule • Spec 1.0 Final Release • Available REAL SOON NOW • Reference Implementation • Final Version REAL SOON NOW • 1.1 • Starting now • Preliminary specs by Summer time

XML Futures • Participate in spec evolution • XSL/XSLT • Schemas • Xlink / Xpointer • XQL • Code • JAXP under consideration for Core • Work with Apache • Work with OASIS

Summary • XML, What it is: • Portable Data • XML and the Java™ Platform • Portable Code + Portable Data • JAXP Overview • Roadmap

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The Java™ Platform and XML