DOSUG XML Beans overview by Om Sivanesian

XMLBeans

- Accessing XML by binding it to Java types.

XMLBeans

Introduction

XMLBeans Architecture

Compiling XML Schema

Conversions & Validation

XmlCursor

Competing Technologies

Sample Code

Questions

Introduction to XMLBeans

Utilizes the full power of XML in Java

Maps the features of XML Schema to Java Types.

Underlying XML Store allows full access to the entire XML infoset when needed

Generated Java Classes allow Java-friendly access to XML

David Bau started it in BEA and was donated to Apache.

Advantages of XMLBeans

Full XML Schema Support

Full XML Infoset Access

Open technology

Enterprise Standard XML Technology

Make XML Schema easy to use

Important APIs of XMLBeans

XmlObject

Super-most type of the generated interfaces/ classes

XmlCursor

Represents a postion in the XML & provides low-level access to the XML Infoset

SchemaType

Provides a full Schema Object Model

XMLBeans Architecture XML Schema Schema compilation extends XML Schema Binaries Generated classes Application XmlBeans jar SchemaType XMLObject XML API XMLCursor

XMLBeans Architecture (contd.) XML Doc XML Store Validation Parse & Load Reads/ Updates SchemaType XMLObject XML API XMLCursor

Schema Compilation XML Schema Schema Validation Schema Object Model Generated Interfaces/Classes Schema Binaries (.xsb) Compiled Interfaces/Classes XML Types jar Built-in Schema Types

XMLBeans Generated Classes

Schema’s targetNamespace becomes package name

Global elements and types become top-level classes

Anonymous types become inner classes

Local elements and attributes become properties

Simple type properties have both Java and XML set/get

XML To Java Conversions

A Document Interface represents the XML

Use its Factory to parse the XML

From the Document Object get the root object.

Access other information using the getters.

Use the validate() method of the Document Object to check for validity.

Java To XML Conversions

Create a new instance of the Document using its Factory.

From the Document create the Root Object.

Assign values and other objects to it.

The toString() method of the Document gives the XML.

Use the validate() method of the Document Object to check for validity.

XML Cursor

A different way to work with XML

A location in an XML Instance not a Node

Lighter weight than Node based model

Fewer Objects = Less Memory, Less Garbage Collection

Access to full XML Infoset (comments, PIs, whitespace)

Similar to moving a cursor through a text document

<Basket>

<Item>

<Category>First</Category>

</Item>

</Basket>

XmlCursor’s programming model is token based.

XML Tokens

STARTDOC

ENDDOC

START

END

TEXT

ATTR

NAMESPACE

COMMENT

PROCINST

Uses of XmlCursor

XmlToken’s newCursor() gives an XmlCursor

Navigation

Many methods are provided to navigate.

e.g:

aCursor.toParent();

aCursor.toFirstChild();

aCursor.toNextChar();

aCursor.toNextAttribute();

aCursor.toNextSibling();

Uses of XmlCursor (contd.)

To add new elements

Use toNextToken() to go past the STARTDOC token.

Use beginElement(elementName, namespace) to create a new element.

Use insertChars(“value”) to create a text value.

Using XPath to obtain data.

selectPath(aXPath) method returns selections.

Use toNextSelection() to iterate through the selections.

XMLBeans Tools

inst2xsd (Instance to Schema Tool)

Generates XML schema from XML instance files.

scomp (Schema Compiler)

Compiles a schema into XMLBeans classes and metadata.

scopy (Schema Copier)

Copies the XML schema at the specified URL to the specified file.

sdownload (Schema Downloader)

Maintains "xsdownload.xml," an index of locally downloaded XSD files. URLs that are specified are downloaded if they aren't already cached. If no files or URLs are specified, all indexed files are relevant.