2002 prentice hall, inc. all rights reserved. chapter 8 – document object model (dom) outline...

2002 Prentice Hall, Inc. All rights reserved.

Chapter 8 – Document Object Model (DOM)

Outline8.1 Introduction8.2 DOM Implementation8.3 DOM with JavaScript8.4 Setup8.5 DOM Components8.6 Creating Nodes8.7 Traversing the DOM8.8 Case Study: Modify the Day Planner Application to Use the DOM


8.1 Introduction

• XML Document Object Model (DOM)– W3C standard recommendation

– Build tree structure in memory for XML documents

– DOM-based parsers parse these structures• Exist in several languages (Java, C, C++, Python, Perl, etc.)

8.1 Introduction

• DOM tree– Each node represents an element, attribute, etc.

<?xml version = "1.0"?><message from = "Paul" to = "Tem"> <body>Hi, Tim!</body></message>

• Node created for element message– Element message has child node for body element

– Element body has child node for text "Hi, Tim!"– Attributes from and to also have nodes in tree


8.2 DOM Implementations

• DOM-based parsers– Microsoft’s msxml

– Sun Microsystem’s JAXP


Fig. 8.1 Some DOM-based parsers. Parser Description

JAXP Sun Microsystem’s Java API for XML Parsing (JAXP) is available at no charge from java.sun.com/xml.

XML4J IBM’s XML Parser for Java (XML4J) is available at no charge from www.alphaworks.ibm.com/tech/xml4j.

Xerces Apache’s Xerces Java Parser is available at no charge from xml.apache.org/xerces.

msxml Microsoft’s XML parser (msxml) version 2.0 is built-into Internet Explorer 5.5. Version 3.0 is also available at no charge from msdn.microsoft.com/xml.

4DOM 4DOM is a parser for the Python programming language and is available at no charge from fourthought.com/4Suite/4DOM.

XML::DOM XML::DOM is a Perl module that we use in Chapter 17 to manipulate XML documents using Perl. For additional information, visit www-4.ibm.com/software/developer/library/xml-perl2.


8.3 DOM and JavaScript

• We use JavaScript and msxml parser– XML document marks up article

– Use DOM API to display document’s element names/values

Outline

Fig. 8.2 Article marked up with XML tags.

1 <?xml version = "1.0"?>

2

3 

4 

5

6 <article>

7

8 <title>Simple XML</title>

9

10 <date>December 6, 2000</date>

11

12 <author>

13 <fname>Tem</fname>

14 <lname>Nieto</lname>

15 </author>

16

17 <summary>XML is pretty easy.</summary>

18

19 <content>Once you have mastered HTML, XML is easily

20 learned. You must remember that XML is not for

21 displaying information but for managing information.

22 </content>

23

24 </article>

Outline

Fig. 8.3 Traversing article.xml with JavaScript.

Element script allows for including scripting code

Instantiate Microsoft XML DOM object

Load article.xml into memory; msxml parses article.xml and stores it as tree structure

1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"

2 "http://www.w3.org/TR/html4/strict.dtd">

3

4 <html>

5

6 

7 

8

9 <head>

10 <title>A DOM Example</title>

11 </head>

12

13 <body>

14

15 <script type = "text/javascript" language = "JavaScript">

16

17 var xmlDocument = new ActiveXObject( "Microsoft.XMLDOM" );

18

19 xmlDocument.load( "article.xml" );

20

Element script allows for including scripting code

Instantiate Microsoft XML DOM object

Load article.xml into memory; msxml parses article.xml and

stores it as tree structure

Outline

Fig. 8.3 Traversing article.xml with JavaScript. (Part 2)

Assign article as root element

Place root element’s name in element strong and write it to browser

Assign index to each child node of root node

Retrieve root node’s first child node (title)

21 // get the root element

22 var element = xmlDocument.documentElement;

23

24 document.writeln(

25 "Here is the root node of the document:" );

26 document.writeln( "" + element.nodeName

27 + "" );

28

29 document.writeln(

30 " The following are its child elements:" );

31 document.writeln( "<ul>" );

32

33 // traverse all child nodes of root element

34 for ( i = 0; i < element.childNodes.length; i++ ) {

35 var curNode = element.childNodes.item( i );

36

37 // print node name of each child element

38 document.writeln( "<li>" + curNode.nodeName

39 + "</li>" );

40 }

41

42 document.writeln( "</ul>" );

43

44 // get the first child node of root element

45 var currentNode = element.firstChild;

46

Assign article as root element

Place root element’s name in element strong and write it to browser

Assign index to each child node of root node

Retrieve root node’s first child node (title)

Outline

Fig. 8.3 Traversing article.xml with JavaScript. (Part 3)

Siblings are nodes at same level in document (e.g., title, date, author, summary and content)

Get first child’s next sibling (date)

Get first child of date (December 6, 2000)

Get parent of date (article)

47 document.writeln( "The first child of root node is:" );

48 document.writeln( "" + currentNode.nodeName

49 + "" );

50 document.writeln( " whose next sibling is:" );

51

52 // get the next sibling of first child

53 var nextSib = currentNode.nextSibling;

54

55 document.writeln( "" + nextSib.nodeName

56 + "." );

57 document.writeln( " Value of " + nextSib.nodeName

58 + " element is:" );

59

60 var value = nextSib.firstChild;

61

62 // print the text value of the sibling

63 document.writeln( "" + value.nodeValue + "" );

64 document.writeln( " Parent node of " );

65 document.writeln( "<string>" + nextSib.nodeName

66 + " is:" );

67 document.writeln( "" + nextSib.parentNode.nodeName

68 + "." );

69

70 </script>

71

72 </body>

73 </html>

Siblings are nodes at same level in document (e.g., title, date,

author, summary and content)

Get first child’s next sibling (date)

Get first child of date (December 6, 2000)

Get parent of date (article)


Fig. 8.3 Traversing article.xml with JavaScript.


8.4 Setup

• Java applications to illustrate DOM API– Java 2 Standard Edition required

• Download at www.java.sun.com/j2se• Installation instructions

– www.deitel.com/faq/java3install.htm

– JAXP required• Download at java.sun.com/xml/download.html


8.5 DOM Components

• Manipulate XML document– Use Java, JAXP and XML-related Java packages


Fig. 8.4 DOM classes and interfaces.

Class/Interface Description

Document interface Represents the XML document’s top-level node, which provides access to all the document’s nodes—including the root element.

Node interface Represents an XML document node.

NodeList interface Represents a read-only list of Node objects.

Element interface Represents an element node. Derives from Node.

Attr interface Represents an attribute node. Derives from Node.

CharacterData interface Represents character data. Derives from Node.

Text interface Represents a text node. Derives from CharacterData.

Comment interface Represents a comment node. Derives from CharacterData.

ProcessingInstruction interface

Represents a processing instruction node. Derives from Node.

CDATASection interface Represents a CDATA section. Derives from Text.


Fig. 8.5 Some Document methods.

Method Name Description

createElement Creates an element node.

createAttribute Creates an attribute node.

createTextNode Creates a text node.

createComment Creates a comment node.

createProcessingInstruction Creates a processing instruction node.

createCDATASection Creates a CDATA section node.

getDocumentElement Returns the document’s root element.

appendChild Appends a child node.

getChildNodes Returns the child nodes.


Fig. 8.6 XmlDocument methods.


createXmlDocument Parses an XML document.

write Outputs the XML document.


Fig. 8.7 Node methods.


appendChild Appends a child node.

cloneNode Duplicates the node.

getAttributes Returns the node’s attributes.

getChildNodes Returns the node’s child nodes.

getNodeName Returns the node’s name.

getNodeType Returns the node’s type (e.g., element, attribute, text, etc.). Node types are described in greater detail in Fig. 8.9.

getNodeValue Returns the node’s value.

getParentNode Returns the node’s parent.

hasChildNodes Returns true if the node has child nodes.

removeChild Removes a child node from the node.

replaceChild Replaces a child node with another node.

setNodeValue Sets the node’s value.

insertBefore Appends a child node in front of a child node.


Fig. 8.8 Some node types.

Node Type Description

Node.ELEMENT_NODE Represents an element node.

Node.ATTRIBUTE_NODE Represents an attribute node.

Node.TEXT_NODE Represents a text node.

Node.COMMENT_NODE Represents a comment node.

Node.PROCESSING_INSTRUCTION_NODE Represents a processing instruction node.

Node.CDATA_SECTION_NODE Represents a CDATA section node.


Fig. 8.9 Element methods.


getAttribute Returns an attribute’s value.

getTagName Returns an element’s name.

removeAttribute Removes an element’s attribute.

setAttribute Sets an attribute’s value.


8.5 DOM Components (cont.)

• Our first Java-based example:– Validates intro.xml– Replaces text in element message with new text


Outline

Fig. 8.10Simple example to replace an existing text node.

import specifies location of classes needed by application

Declare reference to Document object

DocumentBuilder-Factory (parser) will create Document-Builder

Require parser to validate documents

Interface for loading and parsing documents

1 // Fig 8.10 : ReplaceText.java

2 // Reads intro.xml and replaces a text node.

3

4 import java.io.*;

5 import org.w3c.dom.*;

6 import javax.xml.parsers.*;

7 import com.sun.xml.tree.XmlDocument;

8 import org.xml.sax.*;

9

10 public class ReplaceText {

11 private Document document;

12

13 public ReplaceText()

14 {

15 try {

16

17 // obtain the default parser

18 DocumentBuilderFactory factory =

19 DocumentBuilderFactory.newInstance();

20

21 // set the parser to validating

22 factory.setValidating( true );

23

24 DocumentBuilder builder = factory.newDocumentBuilder();

25

import specifies location of classes needed by application

Declare reference to Document object

DocumentBuilderFactory (parser) will create

DocumentBuilder

Require parser to validate documents

Interface for loading and parsing documents


Outline

Fig. 8.10Simple example to replace an existing text node. (Part 2)

Load and parse document (intro.xml)

Get document root node

Test if root node is element

Cast root node as element, then get list of all message elements in document

If message element exists, replace old text node with new one

26 // set error handler for validation errors27 builder.setErrorHandler( new MyErrorHandler() );2829 // obtain document object from XML document30 document = builder.parse( new File( "intro.xml" ) );3132 // fetch the root node33 Node root = document.getDocumentElement();3435 if ( root.getNodeType() == Node.ELEMENT_NODE ) {36 Element myMessageNode = ( Element ) root;37 NodeList messageNodes = 38 myMessageNode.getElementsByTagName( "message" );3940 if ( messageNodes.getLength() != 0 ) {41 Node message = messageNodes.item( 0 );4243 // create a text node44 Text newText = document.createTextNode(45 "New Changed Message!!" );4647 // get the old text node48 Text oldText =49 ( Text ) message.getChildNodes().item( 0 ); 5051 // replace the text 52 message.replaceChild( newText, oldText );53 }54 } 55

Load and parse document (intro.xml)

Get document root node

Test if root node is element

Cast root node as element, then get list of all message

elements in document

If message element exists, replace old text node with new one


Outline

Fig. 8.10Simple example to replace an existing text node. (Part 3)

Write new XML document to intro1.xml

Handles errors that may have occurred

Method main starts application

Output for Fig. 8.10

56 ( (XmlDocument) document).write( new FileOutputStream(57 "intro1.xml" ) ); 58 } 59 catch ( SAXParseException spe ) {60 System.err.println( "Parse error: " + 61 spe.getMessage() );62 System.exit( 1 );63 }64 catch ( SAXException se ) {65 se.printStackTrace(); 66 }67 catch ( FileNotFoundException fne ) {68 System.err.println( "File \'intro.xml\' not found. " );69 System.exit( 1 );70 }71 catch ( Exception e ) {72 e.printStackTrace();73 }74 }75 76 public static void main( String args[] )77 {78 ReplaceText d = new ReplaceText(); 79 }80 }

Write new XML document to intro1.xml

Handles errors that may have occurred

Method main starts application

set PATH=%PATH%;C:\jdk1.3\bin\set CLASSPATH=%CLASSPATH%;C:\jaxp\jaxp.jar;C:\jaxp\parser.jar;.javac ReplaceText.java MyErrorHandler.javajava ReplaceText


Outline

Fig. 8.11Class definition for MyErrorHandler.

ReplaceText (Fig.8.10) instantiates MyErrorHandler to throw exceptions upon errors

1 // Fig 8.11 : MyErrorHandler.java2 // Error Handler for validation errors.34 import org.xml.sax.ErrorHandler;5 import org.xml.sax.SAXException;6 import org.xml.sax.SAXParseException;78 public class MyErrorHandler implements ErrorHandler 9 {1011 // throw SAXException for fatal errors12 public void fatalError( SAXParseException exception )13 throws SAXException 14 {15 throw exception;16 }1718 public void error( SAXParseException e )19 throws SAXParseException20 {21 throw e;22 }2324 // print any warnings 25 public void warning( SAXParseException err )26 throws SAXParseException27 {28 System.err.println( "Warning: " + err.getMessage() );29 }30 }

ReplaceText (Fig.8.10) instantiates MyErrorHandler to throw exceptions upon errors

Outline

Fig. 8.12Input document (intro.xml).

XML document manipulated by ReplaceText Java applciation


2

3 

4 

5

6 <!DOCTYPE myMessage [

7 <!ELEMENT myMessage ( message )>

8 <!ELEMENT message ( #PCDATA )>

9 ]>

10

11 <myMessage>

12 <message>Welcome to XML!</message>

13 </myMessage>

XML document manipulated by ReplaceText Java applciation

Outline

Fig. 8.13Ouput of replaceText.java, which is stored in intro1.xml.

ReplaceText application creates this XML document

1 <?xml version = "1.0" encoding = "UTF-8"?>

2

3 

4 

5

6 <!DOCTYPE myMessage [

7 <!ELEMENT myMessage ( message )>

8 <!ELEMENT message ( #PCDATA )>

9 ]>

10

11 <myMessage>

12 <message>New Changed Message!!</message>

13 </myMessage>

ReplaceText application creates this XML document


8.6 Creating Nodes

• Create XML document at run time– BuildXML Java application

• creates document for contact list


Outline

Fig. 8.14Building an XML document with the DOM.

Use JAXP default parser

DocumentBuilder loads and parses XML documents

1 // Fig. 8.14 : BuildXml.java

2 // Creates element node, attribute node, comment node,

3 // processing instruction and a CDATA section.

4

5 import java.io.*;





10

11 public class BuildXml {


13

14 public BuildXml()

15 {

16



19

20 try {

21

22 // get DocumentBuilder

23 DocumentBuilder builder =

24 factory.newDocumentBuilder();

25

Use JAXP default parser

DocumentBuilder loads and parses XML documents


Outline

Fig. 8.14Building an XML document with the DOM. (Part 2)

Obtain XML Document reference

Create root Element and append to Document

Create Comment node and append to root node

Call method createContactNode (next slide) to create child node

Create Processing-Instruction node with target myInstruction and value action silent

26 // create root node

27 document = builder.newDocument();

28 }

29 catch ( ParserConfigurationException pce ) {

30 pce.printStackTrace();

31 }

32

33 Element root = document.createElement( "root" );

34 document.appendChild( root );

35

36 // add a comment to XML document

37 Comment simpleComment = document.createComment(

38 "This is a simple contact list" );

39 root.appendChild( simpleComment );

40

41 // add a child element

42 Node contactNode = createContactNode( document );

43 root.appendChild( contactNode );

44

45 // add a processing instruction

46 ProcessingInstruction pi =

47 document.createProcessingInstruction(

48 "myInstruction", "action silent" );

49 root.appendChild( pi );

50

Obtain XML Document

reference

Create root Element and append to Document

Create Comment node and append to root node

Call method createContactNode (next

slide) to create child node

Create ProcessingInstruction node with target myInstruction and

value action silent

Outline


Create CDATA node and append to root node

Write XML Document to myDocument.xml

Creates and returns Element node

Create Element FirstName with text Sue

Create Element LastName with text Green

51 // add a CDATA section

52 CDATASection cdata = document.createCDATASection(

53 "I can add <, >, and ?" );

54 root.appendChild( cdata );

55

56 try {

57

58 // write the XML document to a file

59 ( (XmlDocument) document).write( new FileOutputStream(

60 "myDocument.xml" ) );

61 }

62 catch ( IOException ioe ) {

63 ioe.printStackTrace();

64 }

65 }

66

67 public Node createContactNode( Document document )

68 {

69

70 // create FirstName and LastName elements

71 Element firstName = document.createElement( "FirstName" );

72 Element lastName = document.createElement( "LastName" );

73

74 firstName.appendChild( document.createTextNode( "Sue" ) );

75 lastName.appendChild( document.createTextNode( "Green" ) );

76

Create CDATA node and append to root node

Write XML Document to myDocument.xml

Creates and returns Element node

Create Element FirstName with

text Sue

Create Element LastName with

text Green


Outline


Create Element contact with attribute gender

Append Elements FirstName and LastName to Element contact

Return Element contact


77 // create contact element

78 Element contact = document.createElement( "contact" );

79

80 // create an attribute

81 Attr genderAttribute = document.createAttribute( "gender" );

82 genderAttribute.setValue( "F" );

83

84 // append attribute to contact element

85 contact.setAttributeNode( genderAttribute );

86 contact.appendChild( firstName );

87 contact.appendChild( lastName );

88 return contact;

89 }

90

91 public static void main( String args[] )

92 {

93 BuildXml buildXml = new BuildXml();

94 }

95 }

Create Element contact with attribute gender

Append Elements FirstName and LastName to Element

contact

Return Element contact

javac BuildXml.javajava BuildXml

Outline

Fig. 8.14Output for buildXml.java.

1 <?xml version = "1.0" encoding = "UTF-8"?>

2

3 <root>

4 

5 <contact gender = "F">

6 <FirstName>Sue</FirstName>

7 <LastName>Green</LastName>

8 </contact>

9 <?myInstruction action silent?>

10 <![CDATA[I can add <, >, and ?]]>

11 </root>


8.7 Traversing the DOM

• Use DOM to traverse XML document– Output element nodes

– Output attribute nodes

– Output text nodes


Outline

Fig. 8.15Traversing the DOM.

Obtain JAXP default parser and DocumentBuilder to load and parse XML documents

1 // Fig. 8.15 : TraverseDOM.java

2 // Traverses DOM and prints various nodes.

3

4 import java.io.*;





9

10 public class TraverseDOM {


12

13 public TraverseDOM( String file )

14 {

15 try {

16

17 // obtain the default parser



20 factory.setValidating( true );

21 DocumentBuilder builder = factory.newDocumentBuilder();

22

23 // set error handler for validation errors

24 builder.setErrorHandler( new MyErrorHandler() );

25

Obtain JAXP default parser and DocumentBuilder to load and

parse XML documents


Outline

Fig. 8.15Traversing the DOM. (Part 2)

Load and parse XML document

Pass Document to method processNode

Outputs information about argument Node and child elements

switch statement determines Node type

26 // obtain document object from XML document

27 document = builder.parse( new File( file ) );

28 processNode( document );

29 }

30 catch ( SAXParseException spe ) {

31 System.err.println(

32 "Parse error: " + spe.getMessage() );

33 System.exit( 1 );

34 }

35 catch ( SAXException se ) {

36 se.printStackTrace();

37 }

38 catch ( FileNotFoundException fne ) {

39 System.err.println( "File \'"

40 + file + "\' not found. " );


42 }

43 catch ( Exception e ) {

44 e.printStackTrace();

45 }

46 }

47

48 public void processNode( Node currentNode )

49 {

50 switch ( currentNode.getNodeType() ) {

51

Load and parse XML document

Pass Document to method processNode

Outputs information about argument Node

and child elements

switch statement determines Node type

Outline


If document node, output document node and process child nodes

If element node, output element’s attributes and process child nodes

52 // process a Document node53 case Node.DOCUMENT_NODE:54 Document doc = ( Document ) currentNode;5556 System.out.println( 57 "Document node: " + doc.getNodeName() +58 "\nRoot element: " +59 doc.getDocumentElement().getNodeName() );60 processChildNodes( doc.getChildNodes() );61 break;6263 // process an Element node64 case Node.ELEMENT_NODE: 65 System.out.println( "\nElement node: " + 66 currentNode.getNodeName() );67 NamedNodeMap attributeNodes =68 currentNode.getAttributes();6970 for ( int i = 0; i < attributeNodes.getLength(); i++){

71 Attr attribute = ( Attr ) attributeNodes.item( i );

7273 System.out.println( "\tAttribute: " + 74 attribute.getNodeName() + " ; Value = " +75 attribute.getNodeValue() );76 }7778 processChildNodes( currentNode.getChildNodes() );79 break;80

If document node, output document node

and process child nodes

If element node, output element’s attributes and

process child nodes

Outline


If CDATA or text node, output node’s text content

Method process-ChildNodes calls method processNode for each Node in NodeList

Method main starts program

81 // process a text node and a CDATA section82 case Node.CDATA_SECTION_NODE:83 case Node.TEXT_NODE: 84 Text text = ( Text ) currentNode;8586 if ( !text.getNodeValue().trim().equals( "" ) )87 System.out.println( "\tText: " +88 text.getNodeValue() );89 break;90 }91 }9293 public void processChildNodes( NodeList children )94 {95 if ( children.getLength() != 0 ) 9697 for ( int i = 0; i < children.getLength(); i++)98 processNode( children.item( i ) );99 }100101 public static void main( String args[] )102 {103 if ( args.length < 1 ) {104 System.err.println( 105 "Usage: java TraverseDOM <filename>" );106 System.exit( 1 );107 }108109 TraverseDOM traverseDOM = new TraverseDOM( args[ 0 ] ); 110 }111}

If CDATA or text node, output node’s text content

Method processChildNodes calls method processNode for

each Node in NodeList

Method main starts program

Outline

Fig. 8.16Sample execution for TraverseDOM.java.

TraverseDOM application traverses simpleContact.xml


2

3 

4 

5

6 <!DOCTYPE contacts [

7 <!ELEMENT contacts ( contact+ )>

8 <!ELEMENT contact ( FirstName, LastName )>

9 <!ATTLIST contact gender ( M | F ) "M">

10 <!ELEMENT FirstName ( #PCDATA )>

11 <!ELEMENT LastName ( #PCDATA )>

12 ]>

13

14 <contacts>

15 <contact gender = "M">

16 <FirstName>John</FirstName>

17 <LastName>Black</LastName>

18 </contact>

19 </contacts>

TraverseDOM application traverses simpleContact.xml


8.8 Case Study: Modifying the Day Planner Application to Use the DOM

• Continue enhancing day-planner application– Java-based

• Create graphical user interface (GUI)

• Create class that uses DOM to query day planner


Outline

Fig. 8.17Day planner using DOM.

Reference to GUI component that displays output


Constructor initializes application (loads and parses day planner)

1 // Fig. 8.17 : DOMPlanner.java

2 // A day planner application using DOM.

3 // The following program uses Sun's validating parser.

4

5 import java.io.*;

6 import java.awt.*;

7 import java.util.*;

8 import javax.swing.*;

9





14

15 public class DOMPlanner {

16

17 private JTextArea display; // for displaying output

18 private InputSource input; // for reading the XML document

19 private Document document; // document node object

20

21 // variables to store the query parameters and the result

22 private int year, month, day, timePeriod;

23 private String resultYear, resultDay;

24

25 public DOMPlanner( JTextArea output )

26 {

27 year = month = day = timePeriod = -1;

28 display = output;

29

Constructor initializes application (loads and parses day planner)


Reference to parsable XML document


Outline

Fig. 8.17Day planner using DOM. (Part 2)

Obtain JAXP default parser and DocumentBuilder to load and parse XML documents

30 try {3132 // obtain the default parser33 DocumentBuilderFactory factory =34 DocumentBuilderFactory.newInstance();35 factory.setValidating( true );36 DocumentBuilder builder = factory.newDocumentBuilder();3738 // set error handler for validation errors39 builder.setErrorHandler( new MyErrorHandler() );4041 // obtain document object from XML document42 document = builder.parse( new File( "planner.xml" ) );43 } 44 catch ( SAXParseException spe ) {45 System.err.println( "Parse error: " + 46 spe.getMessage() );47 System.exit( 1 );48 }49 catch ( SAXException se ) {50 se.printStackTrace(); 51 }52 catch ( FileNotFoundException fne ) {53 System.err.println( "File \"planner.xml\" not found." );54 System.exit( 1 );55 }56 catch ( Exception e ) {57 e.printStackTrace();58 }59 }60

Obtain JAXP default parser and DocumentBuilder to load and

parse XML documents

Outline


Returns String array containing day-planner document’s years

Retrieve XML document’s root element (planner)

Place all year elements in NodeList

Create String from year elements in NodeList

“Split” space-delimited String into String array

61 // method to get the available years from the XML file

62 public String[] getYears()

63 {

64 String availableYears[];

65 StringTokenizer tokens;

66 String str = " ";

67 int i = 0;

68

69 Element root = document.getDocumentElement();

70 NodeList yearNodes =

71 root.getElementsByTagName( "year" );

72

73 // get value of attribute 'value' for each 'year' node

74 for ( i = 0; i < yearNodes.getLength(); i++ ) {

75 NamedNodeMap yearAttributes =

76 yearNodes.item( i ).getAttributes();

77

78 str += " " + yearAttributes.item( 0 ).getNodeValue();

79 }

80

81 tokens = new StringTokenizer( str );

82 availableYears = new String[ tokens.countTokens() + 1 ];

83 availableYears[ 0 ] = "ANY";

84 i = 1;

85

86 // form an array of strings containing available years

87 while ( tokens.hasMoreTokens() )

88 availableYears[ i++ ] = tokens.nextToken();

89

Returns String array containing day-planner

document’s years

Retrieve XML document’s root element (planner)

Place all year elements in NodeList

Create String from year elements in NodeList

“Split” space-delimited String into String array


Outline


Return String array containing document’s years

Initialize variables (e.g., year, month, etc.) used in query

Call method getResult to process XML document (output query result)

Determine Node type

If Document Node, process Node’s children recursively

90 return availableYears;91 }9293 // method to initialize the query94 public void getQueryResult( int y, int m, int d, int t )95 {96 year = y;97 month = m;98 day = d;99 resultYear = "";100 resultDay = "";101 timePeriod = t;102 display.setText( "*** YOUR DAY PLANNER ***" );103 getResult( document );104 } 105106 // method to output the result of query107 public void getResult( Node node )108 {109 // process each type of node110 // if the node contains child nodes, 111 // process it recursively112 switch ( node.getNodeType() ) {113114 // if it is a Document node process its children115 case Node.DOCUMENT_NODE:116 Document doc = ( Document ) node;117118 getResult( doc.getDocumentElement() );119 break;120

Return String array containing document’s years

Initialize variables (e.g., year, month, etc.) used in query

Call method getResult to process XML document (output query result)

Determine Node type

If Document Node, process Node’s children recursively


Outline


If Element Node, process Node’s according to its name

If planner, process planner’s children

If year, process year’s children

If date, get attributes month and day, then process date’s children

121 // process element node according to its tag name122 case Node.ELEMENT_NODE:123124 if ( node.getNodeName().equals( "planner" ) )125 processChildNodes( node.getChildNodes() );126 else if ( node.getNodeName().equals( "year" ) ) {127128 // find the attribute value for year and 129 // check if it matches the query130 NamedNodeMap yearAttributes = 131 node.getAttributes();132 Node value = yearAttributes.item( 0 );133134 if ( Integer.parseInt( value.getNodeValue() )135 == year || year == -1 ) {136 resultYear = " Y " +137 Integer.parseInt( value.getNodeValue() );138 processChildNodes( node.getChildNodes() );139 }140 else141 return; 142143 }144 else if ( node.getNodeName().equals( "date" ) ) {145 Element dateElement = ( Element ) node;146 int m = Integer.parseInt( 147 dateElement.getAttribute( "month" ) );148 int d = Integer.parseInt( 149 dateElement.getAttribute( "day" ) );150

If Element Node, process Node’s according to its name

If planner, process planner’s children

If year, process year’s children

If date, get attributes month and day, then process date’s children


Outline


If note, get attributes

151 // check if the current 'date' node satisfies query

152 if ( ( m == month && d == day ) ||

153 ( month == -1 && d == day ) ||

154 ( m == month && day == -1 ) ||

155 ( month == -1 && day == -1 ) ) {

156 resultDay = "DATE: D " + d + " M " + m ;

157 processChildNodes(

158 dateElement.getChildNodes() );

159 }

160 else

161 return;

162

163 }

164 else if ( node.getNodeName().equals( "note" ) ) {

165

166 // fetch attributes for the note node and

167 // verify its attribute values with the query

168 NamedNodeMap noteAttributes =

169 node.getAttributes();

170

171 int scheduleTime;

172

If note, get attributes


Outline


Get note appointment time if one was scheduled (i.e., attribute time is present)

If time matches query, display date, time and appointment information

173 if ( noteAttributes.getLength() != 0 ) {

174 Node nodeTime = noteAttributes.item( 0 );

175

176 scheduleTime =

177 Integer.parseInt( nodeTime.getNodeValue() );

178 }

179 else

180 scheduleTime = -1;

181

182 // if the time lies between the periods of the

183 // day display the value of node 'note'

184 if ( isBetween( scheduleTime ) ) {

185 Node child =

186 ( node.getChildNodes() ).item( 0 );

187 String s =

188 child.getNodeValue().trim();

189

190 display.append( "\n" + resultDay +

191 resultYear );

192

193 if ( scheduleTime != -1 )

194 display.append( "\nTIME: " +

195 scheduleTime +" > " + s );

196 else

197 display.append( "\nALL DAY > " + s );

198

Get note appointment time if one was scheduled (i.e.,

attribute time is present)

If time matches query, display date, time and

appointment information

Outline


Iterate and process NodeList (i.e., element’s child nodes)

199 display.append( "\n* * * * * * * * * *" );

200 }

201 else

202 return;

203 }

204 break;

205 }

206 }

207

208 // method to process child nodes

209 public void processChildNodes( NodeList children )

210 {

211 if ( children.getLength() != 0 )

212

213 for ( int i = 0; i < children.getLength(); i++ )

214 getResult( children.item( i ) );

215

216 return;

217 }

218

Iterate and process NodeList (i.e., element’s child nodes)

Outline


Check time value of appointment against query

219 // method to compare the time with various periods

220 // of the day

221 public boolean isBetween( int time )

222 {

223 switch ( timePeriod ) {

224

225 case -1: // add day

226 return true;

227

228 case 0: // morning

229

230 if ( time >= 500 && time < 1200 )

231 return true;

232

233 break;

234

235 case 1: // afternoon

236

237 if ( time >= 1200 && time < 1800 )

238 return true;

239

240 break;

241

242 case 2: // evening

243

Check time value of appointment against query

Outline


244 if ( time >= 1800 && time < 2100 ) 245 return true;246247 break;248249 case 3: // night250251 if ( time >= 2100 || time < 500 )252 return true;253254 break;255256 default:257 System.out.println( "Illegal time in XML file" );258 }259260 return false;261 }262}


Outline

Fig. 8.18Interface for day planner.

Create GUI

Instantiate DOMPlanner object

1 // Fig. 8.18 : DayPlanner.java2 // Program for GUI interface for the day planner application.34 import java.awt.*; 5 import java.awt.event.*; 6 import javax.swing.*; 7 import javax.swing.event.*;89 public class DayPlanner extends JFrame10 implements ActionListener {1112 // GUI components13 private JTextArea display;14 private JComboBox year, month, day, time;15 private JButton query;16 private JPanel panel1, panel2;17 private DOMPlanner handler;1819 public DayPlanner()20 {21 super( "Day planner using DOM" );2223 // set the output font 24 Font font = new Font( "Monospaced",25 java.awt.Font.BOLD, 16 );26 display = new JTextArea();27 display.setFont( font );28 display.setEditable( false );29 30 handler = new DOMPlanner( display );31

Create GUI

Instantiate DOMPlanner object

Outline

Fig. 8.18Interface for day planner. (Part 2)

Populate JComboBox with method getYears of class DOMPlanner

Create other JComboBoxs and populate them with month, day and time, respectively

32 // initialize the user interface components

33 year = new JComboBox( handler.getYears() );

34

35 String months[] = new String[ 13 ];

36 months[ 0 ] = "ANY";

37

38 for ( int i = 1; i < 13; i++ )

39 months[ i ] = Integer.toString( i );

40

41 month = new JComboBox( months );

42

43 String days[] = new String[ 32 ];

44 days[ 0 ] = "ANY";

45

46 for ( int i = 1; i < 32; i++ )

47 days[ i ] = Integer.toString( i );

48

49 day = new JComboBox( days );

50

51 String times[] = { "ANY", "Morning", "Afternoon",

52 "Evening", "Night" };

53 time = new JComboBox( times );

54

55 query = new JButton( "Get Schedules" );

56 query.addActionListener( this );

57

Populate JComboBox with method getYears of class

DOMPlanner

Create other JComboBoxs and populate them with month, day

and time, respectively


Outline


58 // panel containing components for querying

59 panel1 = new JPanel();

60 panel1.setLayout( new GridLayout( 4, 2 ) );

61 panel1.add( new JLabel( "Year" ) );

62 panel1.add( year );

63 panel1.add( new JLabel( "Month" ) );

64 panel1.add( month );

65 panel1.add( new JLabel( "Day" ) );

66 panel1.add( day );

67 panel1.add( new JLabel("Time") );

68 panel1.add( time );

69

70 // panel containing text area for output

71 // and panel2 containing other GUI components.

72 panel2 = new JPanel();

73 panel2.setLayout( new GridLayout( 1, 2 ) );

74 panel2.add( panel1 );

75 panel2.add( query );

76

77 Container c = getContentPane();

78 c.setLayout( new BorderLayout() );

79 c.add( new JScrollPane( display ), BorderLayout.CENTER );

80 c.add( panel2, BorderLayout.SOUTH );

81 setSize( 600, 450 );

82 show();

83 }

84


Outline


Method action-Performed is invoked when user presses Get Schedules button

JComboBox values are passed to method getQueryResult of class DOMPlanner to perform query

85 // method executed when query button is pressed86 public void actionPerformed( ActionEvent e )87 {88 if ( e.getSource() == query ) {89 int yearIndex, monthIndex, dayIndex, timeIndex;9091 // get the integer values of all the query parameters92 yearIndex =93 getIntegerValue( ( String ) year.getSelectedItem() );

94 monthIndex =95 getIntegerValue( ( String ) month.getSelectedItem() );

96 dayIndex =97 getIntegerValue( ( String ) day.getSelectedItem() );98 timeIndex = time.getSelectedIndex() - 1;99100 // get the result of query101 handler.getQueryResult( yearIndex, monthIndex,102 dayIndex, timeIndex );103 }104 }105106 // method to convert the string value to integer107 public int getIntegerValue( String str )108 {109 // if the value 'ANY' is selected, return -1110 if ( str.equals( "ANY" ) )111 return -1;112 else113 return Integer.parseInt( str );114 }115

Method actionPerformed is invoked when user presses

Get Schedules button

JComboBox values are passed to method getQueryResult

of class DOMPlanner to perform query


Outline


116 public static void main( String s[] )

117 {

118 DayPlanner d = new DayPlanner();

119

120 d.addWindowListener(

121 new WindowAdapter()

122 {

123 public void windowClosing( WindowEvent e )

124 {


126 }

127 }

128 );

129 }

130}

2002 prentice hall, inc. all rights reserved. chapter 8 – document object model (dom) outline...

Documents