1

Java and XML

Modified from presentation by:Barry Burd

Drew Universityme@BarryBurd.com

Portions © 2002 Hungry Minds, Inc.

2

Outline

• Review of XML

• Discussion of some Java XML APIs including– SAX– DOM

3

Review of XML

<?xml version="1.0" encoding="UTF-8"?><Greeting type="friendly"> Hello</Greeting>

Start tagEnd tag

Processing instructionCharacters

(text)

4

Review of XML

<?xml version="1.0" encod<Greeting type="friendly"> Hello</Greeting>

Element

Attribute name

Attribute value

5

Review of XML

<song tempo="&Moderato;"> <measure> <beat> <note pitch="&G;"/> <note pitch="&C;"/> <note pitch="&C;"/> </beat> ...

Empty Elements

Entity references

6

Document Type Definition (DTD)

<?xml version="1.0" encoding="UTF-8"?><!-- Song.dtd -->

<!ELEMENT song (measure*)> <!ATTLIST song tempo CDATA "&Moderato;"><!ELEMENT measure (beat*)><!ELEMENT beat (note*)><!ATTLIST note pitch CDATA #REQUIRED><!ENTITY C "60">...Etc.

7

A Doc that’s not well-formed

<Greeting> Hello world! <Question> How are you? <Question> <!-- Oh, no! This start tag should be an end tag! --> </Greeting>

Comment

8

An Invalid Document<!DOCTYPE Greeting SYSTEM "InvalidDoc.dtd"><Greeting> Hello world! <Question> <!-- No Question element in the DTD --> How are you? </Question> </Greeting>

<?xml version="1.0" encoding="UTF-8"?> <!-- InvalidDoc.dtd --><!ELEMENT Greeting (#PCDATA)>

9

A valid document

<!DOCTYPE Greeting SYSTEM "Greeting.dtd"><Greeting> Hello world! <Question> How are you? </Question></Greeting>

<!-- Greeting.dtd --> <!ELEMENT Greeting (#PCDATA | Question)*><!ELEMENT Question (#PCDATA)>

10

Outline

• Review of XML

• Discussion of some Java XML APIs– What APIs are available– SAX– DOM– Validation, namespaces, etc.– Creating a new XML document using DOM– Using XSL

11

Some of the Java APIs

• JAXP (Java API for XML Processing)– SAX (Simple API for XML)– DOM (Document Object Model)

– JAXP comes standard with J2SE 1.4

– It is installed on cerebro if you use the path /usr/local/linux-jdk1.3.1/bin

12

SAX

• Event driven

• Deals with start tags, end tags, etc.

• No inherent notion of an element

• No inherent notion of nesting

• No in-memory copy of the whole document

13

import javax.xml.parsers.*;import org.xml.sax.*;import java.io.*;class CallSAX{ static public void main(String[] args) throws SAXException, ParserConfigurationException, IOException { SAXParserFactory factory = SAXParserFactory.newInstance(); SAXParser saxParser = factory.newSAXParser(); XMLReader xmlReader = saxParser.getXMLReader(); xmlReader.setContentHandler (new MyContentHandler());

//...(more)

Calling SAX

14

import javax.xml.parsers.*;import org.xml.sax.*;import java.io.*;class CallSAX{ static public void main(String[] args) throws SAXException, ParserConfigurationException, IOException { //...Stuff from previous slide

xmlReader.parse (new File(“weather.xml"). toURL().toString()); }}

Calling SAX

15

A Content Handler

import org.xml.sax.helpers.DefaultHandler;import org.xml.sax.Attributes;

class MyContentHandler extends DefaultHandler{ public void startDocument() { System.out.println ("Starting the document."); }

// More...

16

A Content Handler (cont’d) public void startElement(String uri, String localName, String qualName, Attributes attribs) { System.out.print("Start tag: "); System.out.println(qualName); for (int i=0; i<attribs.getLength(); i++) { System.out.print("Attribute: "); System.out.print(attribs.getQName(i)); System.out.print(" = "); System.out.println(attribs.getValue(i)); } }

17

A Content Handler (cont’d) public void characters (char[] charArray, int start, int length) { String charString = new String(charArray, start, length);

charString = charString.replaceAll("\n", "[cr]"); charString = charString.replaceAll(" ", "[blank]");

System.out.print(length + " characters: "); System.out.println(charString); }

18

A Content Handler (cont’d) public void endElement(String uri, String localName, String qualName) { System.out.print("End tag: "); System.out.println(qualName); }

public void endDocument() { System.out.println("Ending the document."); }}

19

A Sample Document

<?xml version="1.0"?><WeatherReport><City>White Plains</City><State>NY</State><Date>Sat Jul 25 1998</Date><Time>11 am EDT</Time><CurrTemp Unit="Farenheit">70</CurrTemp>

<High Unit="Farenheit">82</High><Low Unit="Farenheit">62</Low></WeatherReport>

20

The Output

Starting the document.Start tag: WeatherReport1 characters: $Start tag: City12 characters: White PlainsEnd tag: City1 characters: $Start tag: State2 characters: NYEnd tag: State1 characters: $Start tag: Date15 characters: Sat Jul 25 1998End tag: Date1 characters: $Start tag: Time9 characters: 11 am EDTEnd tag: Time1 characters: $Start tag: CurrTempAttribute: unit = Farenheit2 characters: 70End tag: CurrTemp1 characters: $Start tag: HighAttribute: unit = Farenheit2 characters: 82End tag: High1 characters: $Start tag: LowAttribute: unit = Farenheit2 characters: 62End tag: Low1 characters: $End tag: WeatherReportEnding the document.

21

DOM

• Not event driven• Creates an in-memory copy of the

document• Deals with document nodes• Nodes are nested• Elements are nodes, but so are attributes,

text, processing instructions, comments, the entire document itself

• No inherent notion of a tag

22

Calling DOM

import javax.xml.parsers.*;import org.xml.sax.SAXException;import java.io.*;import org.w3c.dom.Document;

public class CallDOM{ public static void main(String args[]) throws ParserConfigurationException, SAXException, IOException { DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = factory.newDocumentBuilder(); Document doc;

// More... }}

23

Calling DOM

import javax.xml.parsers.*;import org.xml.sax.SAXException;import java.io.*;import org.w3c.dom.Document;public class CallDOM{ public static void main(String args[]) throws ParserConfigurationException, SAXException, IOException { //... Stuff from previous slide

if (args.length == 1) { doc = builder.parse (new File(args[0]).toURL().toString()); new MyTreeTraverser (doc); } else System.out.println ("Usage: java CallDOM file-name.xml"); }}

24

class MyTreeTraverser{ String indent="";

MyTreeTraverser (Node node) { traverse(node); } void traverse(Node node){ displayName(node); displayValue(node); if (node.getNodeType() == Node.ELEMENT_NODE) displayAttributes(node);

indent=indent.concat(" "); displayChildren(node); indent=indent.substring(0,indent.length()-3); } // …stuff void displayChildren(Node node) { Node child = node.getFirstChild(); while (child != null) { traverse(child); child = child.getNextSibling(); } }

A Tree Traverser

25

The Output

Name: #documentValue: null Name: WeatherReport Value: null Name: #text Value: Name: City Value: null Name: #text Value: White Plains Name: #text Value: Name: State Value: null Name: #text Value: NY Name: #text Value: Name: Date Value: null Name: #text Value: Sat Jul 25 1998 Name: #text Value:

Name: Time Value: null Name: #text Value: 11 am EDT Name: #text Value: Name: CurrTemp Value: null

Attribute: Unit = Farenheit Name: #text Value: 70 Name: #text Value: Name: High Value: null

Attribute: Unit = Farenheit Name: #text Value: 82 Name: #text Value: Name: Low Value: null

Attribute: Unit = Farenheit Name: #text Value: 62 Name: #text Value:

26

Setting an Error Handler

• In SAX: xmlReader.setErrorHandler new MyErrorHandler());

• In DOMbuilder.setErrorHandler (new MyErrorHandler());

27

An Error Handler

import org.xml.sax.helpers.DefaultHandler;import org.xml.sax.SAXParseException;class MyErrorHandler extends DefaultHandler{ public void error(SAXParseException e) { System.out.println("Error:"); showSpecifics(e); System.out.println(); } public void showSpecifics(SAXParseException e) { System.out.println(e.getMessage()); System.out.println (" Line " + e.getLineNumber()); System.out.println (" Column " + e.getColumnNumber()); System.out.println (" Document " + e.getSystemId()); }}

28

import org.xml.sax.helpers.DefaultHandler;import org.xml.sax.SAXParseException;class MyErrorHandler extends DefaultHandler{ public void warning(SAXParseException e) { System.out.println("Warning:"); showSpecifics(e); System.out.println(); } public void fatalError(SAXParseException e) { System.out.println("Fatal error:"); showSpecifics(e); System.out.println(); }

// ...}

An Error Handler (cont’d)

29

Turning on DTD Validation

// must do this before using the factory

factory.setValidating(true);

30

The Output

Error:Attribute value for "Unit" is #REQUIRED. Line 9 Column -1 Document file:/usr/local/www/data/csci380/02s/examples/xml/DOMvalid/weather2.xml

Name: #documentValue: null Name: WeatherReport Value: null Name: WeatherReport Value: null…

31

<?xml-stylesheet type="text/xsl" href="JavaAndXMLforDummies.xsl"?><Book title="Java and XML For Dummies"> <Chapter title="Introduction"> <Section>About This Book</Section> <Section>Conventions Used in This Book</Section> </Chapter> <Part number="I" title="The Big Picture"> <Chapter number="1" title="SAX"> <Section>A "Hello" Example</Section> <Section>Doing Validation</Section> </Chapter> <Chapter number="2" title="DOM"> <Section>A "Hello" Example</Section> <Section>Creating a new document</Section> </Chapter> </Part> <Part title="Appendixes"> <Appendix number="A" title="Things to Remember about Java"> </Appendix> <Appendix number="B" title="Things to Remember about XML"> </Appendix> </Part></Book>

Using XSL

32

<?xml version="1.0"?><xsl:stylesheet xmlns:xsl= http://www.w3.org/1999/XSL/Transform version="1.0"> <xsl:output method="html"/>

<xsl:template match="Book"> <h2><xsl:value-of select="@title"/></h2> <xsl:apply-templates /> </xsl:template> <xsl:template match="Part"> <h2> <xsl:if test="@number">Part <xsl:value-of select="@number"/>: </xsl:if><xsl:value-of select="@title"/> </h2> <xsl:apply-templates /> </xsl:template>

An XSL Stylesheet

33

<xsl:template match="Chapter"> <b>&#160;&#160;&#160;&#160;<xsl:if test="@number">Chapter <xsl:value-of select="@number"/>: </xsl:if><xsl:value-of select="@title"/></b><br/> <xsl:apply-templates /> </xsl:template> <xsl:template match="Section"> #160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#8226;

<xsl:value-of select="."/><br/> </xsl:template> <xsl:template match="Appendix"> <b>&#160;&#160;&#160;&#160;Appendix <xsl:value-of select="@number"/>: <xsl:value-of select="@title"/></b><br/> <xsl:apply-templates /> </xsl:template>

</xsl:stylesheet>

An XSL Stylesheet

(cont’d)

34

JavaAndXMLforDummies.htm<h2>Java and XML For Dummies</h2> <b>&nbsp;&nbsp;&nbsp;&nbsp;Introduction</b><br> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&bull; About This Book<br>

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&bull; Conventions Used in This Book<br>

<h2>Part I: The Big Picture</h2> <b>&nbsp;&nbsp;&nbsp;&nbsp;Chapter 1: SAX</b>

... Etc.

35

Java and XML For Dummies     Introduction

        • About This Book        • Conventions Used in This Book

Part I: The Big Picture     Chapter 1: SAX

        • A "Hello" Example        • Doing Validation    Chapter 2: DOM         • A "Hello" Example        • Creating a new document

Appendixes     Appendix A: Things to Remember about Java

    Appendix B: Things to Remember about XML

36

Applying XSL with Java Codeimport javax.xml.transform.TransformerFactory;import javax.xml.transform.Transformer;import javax.xml.transform.stream.StreamSource;import javax.xml.transform.stream.StreamResult;import javax.xml.transform.TransformerException;import javax.xml.transform.TransformerConfigurationException;import java.io.FileOutputStream;import java.io.FileNotFoundException;import java.io.IOException;

More...

37

Applying XSL with Java Code (cont’d)

public class MyTransform{ public static void main(String[] args) throws TransformerException, TransformerConfigurationException, FileNotFoundException, IOException {

TransformerFactory tFactory = TransformerFactory.newInstance(); Transformer transformer = tFactory.newTransformer (new StreamSource("JavaAndXMLforDummies.xsl")); transformer.transform (new StreamSource("JavaAndXMLforDummies.xml"), new StreamResult (new FileOutputStream("JavaAndXMLforDummies.htm"))); }}

38

The Usual Scenario...

Client Browser

http GET requestfor

JavaAndXMLforDummies.jsp

HTTP server

Servlet container

.xml file.xml file .xsl file.xsl file

.jsp file.jsp file

.htm file.htm file

response