- Sams Teach Yourself XML in 21 Days, Third Edition
- Table of Contents
- About the Author
- Acknowledgments
- We Want to Hear from You!
- Introduction
- Part I: At a Glance
- Day 1. Welcome to XML
- All About Markup Languages
- All About XML
- Looking at XML in a Browser
- Working with XML Data Yourself
- Structuring Your Data
- Creating Well-Formed XML Documents
- Creating Valid XML Documents
- How XML Is Used in the Real World
- Online XML Resources
- Summary
- Q&A
- Workshop
- Day 2. Creating XML Documents
- Choosing an XML Editor
- Using XML Browsers
- Using XML Validators
- Creating XML Documents Piece by Piece
- Creating Prologs
- Creating an XML Declaration
- Creating XML Comments
- Creating Processing Instructions
- Creating Tags and Elements
- Creating CDATA Sections
- Handling Entities
- Summary
- Q&A
- Workshop
- Day 3. Creating Well-Formed XML Documents
- What Makes an XML Document Well-Formed?
- Creating an Example XML Document
- Understanding the Well-Formedness Constraints
- Using XML Namespaces
- Understanding XML Infosets
- Understanding Canonical XML
- Summary
- Q&A
- Workshop
- Day 4. Creating Valid XML Documents: DTDs
- All About DTDs
- Validating a Document by Using a DTD
- Creating Element Content Models
- Commenting a DTD
- Supporting External DTDs
- Handling Namespaces in DTDs
- Summary
- Q&A
- Workshop
- Declaring Attributes in DTDs
- Day 5. Handling Attributes and Entities in DTDs
- Specifying Default Values
- Specifying Attribute Types
- Handling Entities
- Summary
- Q&A
- Workshop
- Day 6. Creating Valid XML Documents: XML Schemas
- Using XML Schema Tools
- Creating XML Schemas
- Dissecting an XML Schema
- The Built-in XML Schema Elements
- Creating Elements and Types
- Specifying a Number of Elements
- Specifying Element Default Values
- Creating Attributes
- Summary
- Q&A
- Workshop
- Day 7. Creating Types in XML Schemas
- Restricting Simple Types by Using XML Schema Facets
- Creating XML Schema Choices
- Using Anonymous Type Definitions
- Declaring Empty Elements
- Declaring Mixed-Content Elements
- Grouping Elements Together
- Grouping Attributes Together
- Declaring all Groups
- Handling Namespaces in Schemas
- Annotating an XML Schema
- Summary
- Q&A
- Workshop
- Part I. In Review
- Well-Formed Documents
- Valid Documents
- Part II: At a Glance
- Day 8. Formatting XML by Using Cascading Style Sheets
- Our Sample XML Document
- Introducing CSS
- Connecting CSS Style Sheets and XML Documents
- Creating Style Sheet Selectors
- Using Inline Styles
- Creating Style Rule Specifications in Style Sheets
- Summary
- Q&A
- Workshop
- Day 9. Formatting XML by Using XSLT
- Introducing XSLT
- Transforming XML by Using XSLT
- Writing XSLT Style Sheets
- Using <xsl:apply-templates>
- Using <xsl:value-of> and <xsl:for-each>
- Matching Nodes by Using the match Attribute
- Working with the select Attribute and XPath
- Using <xsl:copy>
- Using <xsl:if>
- Using <xsl:choose>
- Specifying the Output Document Type
- Summary
- Q&A
- Workshop
- Day 10. Working with XSL Formatting Objects
- Introducing XSL-FO
- Using XSL-FO
- Using XSL Formatting Objects and Properties
- Building an XSL-FO Document
- Handling Inline Formatting
- Formatting Lists
- Formatting Tables
- Summary
- Q&A
- Workshop
- Part II. In Review
- Using CSS
- Using XSLT
- Using XSL-FO
- Part III: At a Glance
- Day 11. Extending HTML with XHTML
- Why XHTML?
- Writing XHTML Documents
- Validating XHTML Documents
- The Basic XHTML Elements
- Organizing Text
- Formatting Text
- Selecting Fonts: <font>
- Comments: <!-->
- Summary
- Q&A
- Workshop
- Day 12. Putting XHTML to Work
- Creating Hyperlinks: <a>
- Linking to Other Documents: <link>
- Handling Images: <img>
- Creating Frame Documents: <frameset>
- Creating Frames: <frame>
- Creating Embedded Style Sheets: <style>
- Formatting Tables: <table>
- Creating Table Rows: <tr>
- Formatting Table Headers: <th>
- Formatting Table Data: <td>
- Extending XHTML
- Summary
- Q&A
- Workshop
- Day 13. Creating Graphics and Multimedia: SVG and SMIL
- Introducing SVG
- Creating an SVG Document
- Creating Rectangles
- Adobe's SVG Viewer
- Using CSS Styles
- Creating Circles
- Creating Ellipses
- Creating Lines
- Creating Polylines
- Creating Polygons
- Creating Text
- Creating Gradients
- Creating Paths
- Creating Text Paths
- Creating Groups and Transformations
- Creating Animation
- Creating Links
- Creating Scripts
- Embedding SVG in HTML
- Introducing SMIL
- Summary
- Q&A
- Workshop
- Day 14. Handling XLinks, XPointers, and XForms
- Introducing XLinks
- Beyond Simple XLinks
- Introducing XPointers
- Introducing XBase
- Introducing XForms
- Summary
- Workshop
- Part III. In Review
- Part IV: At a Glance
- Day 15. Using JavaScript and XML
- Introducing the W3C DOM
- Introducing the DOM Objects
- Working with the XML DOM in JavaScript
- Searching for Elements by Name
- Reading Attribute Values
- Getting All XML Data from a Document
- Validating XML Documents by Using DTDs
- Summary
- Q&A
- Workshop
- Day 16. Using Java and .NET: DOM
- Using Java to Read XML Data
- Finding Elements by Name
- Creating an XML Browser by Using Java
- Navigating Through XML Documents
- Writing XML by Using Java
- Summary
- Q&A
- Workshop
- Day 17. Using Java and .NET: SAX
- An Overview of SAX
- Using SAX
- Using SAX to Find Elements by Name
- Creating an XML Browser by Using Java and SAX
- Navigating Through XML Documents by Using SAX
- Writing XML by Using Java and SAX
- Summary
- Q&A
- Workshop
- Day 18. Working with SOAP and RDF
- Introducing SOAP
- A SOAP Example in .NET
- A SOAP Example in Java
- Introducing RDF
- Summary
- Q&A
- Workshop
- Part IV. In Review
- Part V: At a Glance
- Day 19. Handling XML Data Binding
- Introducing DSOs
- Binding HTML Elements to HTML Data
- Binding HTML Elements to XML Data
- Binding HTML Tables to XML Data
- Accessing Individual Data Fields
- Binding HTML Elements to XML Data by Using the XML DSO
- Binding HTML Tables to XML Data by Using the XML DSO
- Searching XML Data by Using a DSO and JavaScript
- Handling Hierarchical XML Data
- Summary
- Q&A
- Workshop
- Day 20. Working with XML and Databases
- XML, Databases, and ASP
- Storing Databases as XML
- Using XPath with a Database
- Introducing XQuery
- Summary
- Q&A
- Workshop
- Day 21. Handling XML in .NET
- Creating and Editing an XML Document in .NET
- From XML to Databases and Back
- Reading and Writing XML in .NET Code
- Using XML Controls to Display Formatted XML
- Creating XML Web Services
- Summary
- Q&A
- Workshop
- Part V. In Review
- Appendix A. Quiz Answers
- Quiz Answers for Day 1
- Quiz Answers for Day 2
- Quiz Answers for Day 3
- Quiz Answers for Day 4
- Quiz Answers for Day 5
- Quiz Answers for Day 6
- Quiz Answers for Day 7
- Quiz Answers for Day 8
- Quiz Answers for Day 9
- Quiz Answers for Day 10
- Quiz Answers for Day 11
- Quiz Answers for Day 12
- Quiz Answers for Day 13
- Quiz Answers for Day 14
- Quiz Answers for Day 15
- Quiz Answers for Day 16
- Quiz Answers for Day 17
- Quiz Answers for Day 18
- Quiz Answers for Day 19
- Quiz Answers for Day 20
- Quiz Answers for Day 21
Using SAX to Find Elements by Name
Yesterday you were able to use the getElementsByTagName method to search an XML document for a particular element, but using that method isn't an option in SAX. Nonetheless, you can search for particular elements when you use SAX—you just have to wait until they come to you when the parser finds them.
You can build on the SAX parsing program you've already written in a new example, ch17_03.java. You can let the user enter the name of the XML document to search and the name of the element to search for, like this:
%java ch17_03 ch17_01.xml senator
In the main method, store the name of the element the user wants to search for in a variable called findNode:
public static void main(String args[]) { ch17_03 obj = new ch17_03(); findNode = args[1]; obj.childLoop(args[0]); for(int index = 0; index < numberLines; index++){ System.out.println(displayText[index]); } }
In the startElement method, you'll search for that element, and when you find it, set a Boolean named displayBoolean to true. When this Boolean is true, you know that you're inside the element you're looking for and so should be storing data in the displayText array, like this:
public void startElement(String uri, String localName, String qualifiedName, Attributes attributes) { if(qualifiedName.equals(findNode)){ displayBoolean=true; } if (displayBoolean){ displayText[numberLines] = indentation; indentation += " "; displayText[numberLines] += '<'; displayText[numberLines] += qualifiedName; if (attributes != null) { int numberAttributes = attributes.getLength(); for (int loopIndex = 0; loopIndex < numberAttributes; loopIndex++){ displayText[numberLines] += ' '; displayText[numberLines] += attributes.getQName(loopIndex); displayText[numberLines] += "=\""; displayText[numberLines] += attributes.getValue(loopIndex); displayText[numberLines] += '"'; } } displayText[numberLines] += '>'; numberLines++; } }
You'll use the displayBoolean variable in all the methods that the SAX parser calls in your code to see whether you're in the element the user is searching for and so should be storing text in the displayText array. For example, this is how to do that in the characters method, which handles text nodes:
public void characters(char characters[], int start, int length) { if(displayBoolean){ String characterData = (new String(characters, start, length)).trim(); if(characterData.indexOf("\n") < 0 && characterData.length() > 0) { displayText[numberLines] = indentation; displayText[numberLines] += characterData; numberLines++; } } }
When you reach the end of the element you've been searching for, you can set the displayBoolean variable to false:
public void endElement(String uri, String localName, String qualifiedName) { if(displayBoolean){ indentation = indentation.substring(0, indentation.length() - 4); displayText[numberLines] = indentation; displayText[numberLines] += "</"; displayText[numberLines] += qualifiedName; displayText[numberLines] += '>'; numberLines++; } if(qualifiedName.equals(findNode)){ displayBoolean=false; } }
Figure 17.2 shows that we are indeed displaying all the <senator> elements and their contents.
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Figure 17.2 Searching an XML document for elements by using SAX.
The complete code is shown in Listing 17.3.
Example 17.3. Finding XML Elements by Using Java SAX (ch17_03.java)
import java.io.*; import org.xml.sax.*; import javax.xml.parsers.*; import org.xml.sax.helpers.DefaultHandler; public class ch17_03 extends DefaultHandler { static int numberLines = 0; static String indentation = ""; static String displayText[] = new String[1000]; static boolean displayBoolean; static String findNode; public static void main(String args[]) { ch17_03 obj = new ch17_03(); findNode = args[1]; obj.childLoop(args[0]); for(int index = 0; index < numberLines; index++){ System.out.println(displayText[index]); } } public void childLoop(String uri) { DefaultHandler saxHandler = this; SAXParserFactory saxFactory = SAXParserFactory.newInstance(); try { SAXParser saxParser = saxFactory.newSAXParser(); saxParser.parse(new File(uri), saxHandler); } catch (Throwable t) {} } public void startDocument() { if(displayBoolean){ displayText[numberLines] = indentation; displayText[numberLines] += "<?xml version=\"1.0\" encoding=\""+ "UTF-8" + "\"?>"; numberLines++; } } public void processingInstruction(String target, String data) { if(displayBoolean){ displayText[numberLines] = indentation; displayText[numberLines] += "<?"; displayText[numberLines] += target; if (data != null && data.length() > 0) { displayText[numberLines] += ' '; displayText[numberLines] += data; } displayText[numberLines] += "?>"; numberLines++; } } public void startElement(String uri, String localName, String qualifiedName, Attributes attributes) { if(qualifiedName.equals(findNode)) { displayBoolean=true; } if (displayBoolean){ displayText[numberLines] = indentation; indentation += " "; displayText[numberLines] += '<'; displayText[numberLines] += qualifiedName; if (attributes != null) { int numberAttributes = attributes.getLength(); for (int loopIndex = 0; loopIndex < numberAttributes; loopIndex++) { displayText[numberLines] += ' '; displayText[numberLines] += attributes.getQName(loopIndex); displayText[numberLines] += "=\""; displayText[numberLines] += attributes.getValue(loopIndex); displayText[numberLines] += '"'; } } displayText[numberLines] += '>'; numberLines++; } } public void characters(char characters[], int start, int length) { if(displayBoolean){ String characterData = (new String(characters, start, length)).trim(); if(characterData.indexOf("\n") < 0 && characterData.length() > 0) { displayText[numberLines] = indentation; displayText[numberLines] += characterData; numberLines++; } } } public void ignorableWhitespace(char characters[], int start, int length) { if(displayBoolean){ //characters(ch, start, length); } } public void endElement(String uri, String localName, String qualifiedName) { if(displayBoolean){ indentation = indentation.substring(0, indentation.length() - 4) ; displayText[numberLines] = indentation; displayText[numberLines] += "</"; displayText[numberLines] += qualifiedName; displayText[numberLines] += '>'; numberLines++; } if(qualifiedName.equals(findNode)){ displayBoolean=false; } } public void warning(SAXParseException exception) { System.err.println("Warning: " + exception.getMessage()); } public void error(SAXParseException exception) { System.err.println("Error: " + exception.getMessage()); } public void fatalError(SAXParseException exception) { System.err.println("Fatal error: " + exception.getMessage()); } }