<?xml version="1.0"?>
<article>
<articleinfo>
 <title>XSL -- First Step in Learning XML</title>
 <author><firstname>Benoît</firstname>
  <surname>Marchal</surname></author>
</articleinfo>
<sect1><title>The Value of XSL</title>
 <para>This is an excerpt from the September 2000 issue of
  Pineapplesoft Link. To subscribe free visit
  <ulink url="http://www.marchal.com">marchal.com</ulink>.</para>
 <para>Where do you start learning XML? Increasingly my answer
  is with XSL. XSL is a very powerful tool with many
  applications. Many XML applications depend on it. Let's take
  two examples.</para>
</sect1>
<sect1>
 <title>XSL and Web Publishing</title>
 <para>As a webmaster you would benefit from using XSL.</para>
 <para>Let's suppose that you decide to support smartphones.
  You will need to redo your web site using WML, the
  <emphasis>wireless markup language</emphasis>, instead of
  HTML. While learning WML is easy, it can take days if not
  months to redo a large web site. Imagine having to edit every
  single page by hand!</para>
 <para>In contrast with XSL, it suffices to update one style
  sheet the changes flow across the entire web site.</para>
</sect1>
<sect1>
 <title>XSL and Programming</title>
 <para>The second facet of XSL is the scripting language. XSL
  has many features of scripting languages including loops,
  function calls, variables and more.</para>
 <para>In that respect, XSL is a valuable addition to any
  programmer toolbox. Indeed, as XML popularity keeps growing,
  you will find that you need to manipulate XML documents
  frequently and XSL is the language for so doing.</para>
</sect1>
<sect1>
 <title>Conclusion</title>
 <para>If you're serious about learning XML, learn XSL. XSL is
  a tool to manipulate XML documents for web publishing or
  programming.</para>
</sect1>
</article>

<?xml version="1.0" encoding="UTF-8"?>
<txt:root lineWidth="65"
          xmlns:txt="http://www.psol.com/xns/xslist/xml2text">
<txt:block linesAfter="1">This is an excerpt from the September
2000 issue of Pineapplesoft Link. To subscribe free visit
marchal.com.</txt:block>
<txt:root>

This is an excerpt from the September 2000 issue of
Pineapplesoft Link. To subscribe free visit marchal.com.

<?xml version="1.0"?>
<xsl:stylesheet version="1.0"
   xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
   xmlns:txt="http://www.psol.com/xns/xslist/xml2text">

<xsl:output method="xml"/>

<xsl:template match="/">
<txt:root lineWidth="65">
   <xsl:apply-templates/>
</txt:root>
</xsl:template>

<xsl:template match="articleinfo">
   <txt:block linesAfter="0">&gt; <xsl:value-of
       select="title"/> &lt;</txt:block>
   <txt:block linesAfter="2">
       by <xsl:value-of select="author/firstname"/>
       <xsl:value-of select="author/surname"/>
    </txt:block>
</xsl:template>

<xsl:template match="sect1/title">
   <txt:block linesAfter="1">* <xsl:apply-templates/> *</txt:block>
</xsl:template>

<xsl:template match="ulink">
   <xsl:apply-templates/>
   <xsl:text> &lt;</xsl:text>
   <xsl:value-of select="@url"/>
   <xsl:text>&gt;</xsl:text>
</xsl:template>

<xsl:template match="emphasis">
   <xsl:text>*</xsl:text>
   <xsl:apply-templates/>
   <xsl:text>*</xsl:text>
</xsl:template>

<xsl:template match="para">
   <txt:block linesAfter="1"><xsl:apply-templates/></txt:block>
</xsl:template>

</xsl:stylesheet>

package com.psol.xslist;

import java.io.*;
import org.xml.sax.*;
import org.xml.sax.helpers.*;

public class Xml2Text
   extends DefaultHandler
{
   protected static final String
      NAMESPACE_URI = "http://www.psol.com/xns/xslist/xml2text";
   protected static final int NONE = 0,
                              ROOT = 1,
                              BLOCK = 2;
   protected StringBuffer buffer;
   protected int state,
                 lineWidth,
                 linesAfter;
   protected PrintWriter writer = null;

   public Xml2Text(PrintWriter writer)
   {
      this.writer = writer;
   }

   public void startElement(String uri,
                            String name,
                            String qualifiedName,
                            Attributes atts)
   {
      if(!uri.equals(NAMESPACE_URI))
         return;
      if(state == ROOT && name.equals("block"))
      {
         state = BLOCK;
         buffer = new StringBuffer(128);
         try
         {
            linesAfter =
               Integer.parseInt(atts.getValue("linesAfter"));
         }
         catch(NumberFormatException e)
         {
            linesAfter = 0;
         }
      }
      else if(state == NONE && name.equals("root"))
      {
         state = ROOT;
         try
         {
            lineWidth =
               Integer.parseInt(atts.getValue("lineWidth"));
         }
         catch(NumberFormatException e)
         {
            lineWidth = 65;
         }
      }
   }

   public void endElement(String uri,
                          String name,
                          String qualifiedName)
   {
      if(!uri.equals(NAMESPACE_URI))
         return;
      if(state == BLOCK && name.equals("block"))
      {
         state = ROOT;
         int start = 0,
             current = start,
             lastSpace = start - 1;
         while(current < buffer.length())
         {
            while(current < start + lineWidth &&
                  current < buffer.length())
            {
               if(Character.isWhitespace(buffer.charAt(current)))
                  lastSpace = current;
               current++;
            }
            if(current < buffer.length() && start < lastSpace)
            {
               for(int i = start;i < lastSpace;i++)
                  writer.print(buffer.charAt(i));
               start = lastSpace + 1;
            }
            else
            {
               for(int i = start;i < current;i++)
                  writer.print(buffer.charAt(i));
               start = current;
            }
            current = start;
            lastSpace = start - 1;
            writer.println();
         }
         for(int i = 0;i < linesAfter;i++)
            writer.println();
         buffer.delete(0,buffer.length());
      }
      else if(state == ROOT && name.equals("root"))
         state = NONE;
   }

   public void characters(char[] chars,int start,int length)
   {
      if(state == BLOCK)
         buffer.append(chars,start,length);
   }

   public void startDocument()
   {
      state = NONE;
   }

   public void endDocument()
   {
      writer.flush();
   }
}

SAX defined

The most important events are startElement(), endElement(), and characters().

SAX filters are special event handlers designed to be chained with each other. The second installment of this article series will revisit SAX.

package com.psol.xslist;

import java.util.*;
import org.xml.sax.*;
import org.xml.sax.helpers.*;

public class WhitespaceFilter
   extends XMLFilterImpl
{
   protected Stack stack;

   public WhitespaceFilter()
   {
      super();
   }

   public WhitespaceFilter(XMLReader reader)
   {
      super(reader);
   }

   public void startElement(String uri,
                            String name,
                            String qualifiedName,
                            Attributes atts)
      throws SAXException
   {
      String space = atts.getValue("xml:space");
      if(null != space && space.equals("preserve"))
         stack.push(null);
      else
         stack.push(new StringBuffer());
      super.startElement(uri,name,qualifiedName,atts);
   }

   public void endElement(String uri,
                          String name,
                          String qualifiedName)
      throws SAXException
   {
      Object object = stack.pop();
      if(object instanceof StringBuffer)
      {
         StringBuffer input = (StringBuffer)object,
                      output = new StringBuffer();
         boolean wasWhitespace = false;
         for(int current = 0;current < input.length();current++)
         {
            char c = input.charAt(current);
            if(c == '\n' || c == '\r')
               c = ' ';
            if(Character.isWhitespace(c))
            {
               if(!wasWhitespace)
                  output.append(c);
               wasWhitespace = true;
            }
            else
            {
               output.append(c);
               wasWhitespace = false;
            }
         }
         char[] chars = new char[output.length()];
         output.getChars(0,output.length(),chars,0);
         super.characters(chars,0,output.length());
      }
      super.endElement(uri,name,qualifiedName);
   }

   public void characters(char[] chars,int start,int length)
      throws SAXException
   {
      Object object = stack.peek();
      if(object instanceof StringBuffer)
         ((StringBuffer)object).append(chars,start,length);
      else
         super.characters(chars,start,length);
   }

   public void startDocument()
      throws SAXException
   {
      stack = new Stack();
      super.startDocument();
   }
}

package com.psol.xslist;

import java.io.*;
import org.xml.sax.*;
import org.xml.sax.helpers.*;

public class AsciiFilter
   extends XMLFilterImpl
{
   public AsciiFilter()
   {
      super();
   }

   public AsciiFilter(XMLReader reader)
   {
      super(reader);
   }

   public void characters(char[] chars,int start,int length)
      throws SAXException
   {
      StringBuffer filtered =
         new StringBuffer((int)(length * 1.1));
      int i = start,
          stop = start + length;
      while(i < stop)
      {
         char c = chars[i++];
         switch(c)
         {
            case '?x009C;':
               filtered.append("oe");
               break;
            case '©':
               filtered.append("(c)");
               break;
            case 'à':
            case 'ä':
               filtered.append('a');
               break;
            case 'æ':
               filtered.append("ae");
               break;
            case 'ç':
               filtered.append('c');
               break;
            case 'è':
            case 'é':
            case 'ê':
            case 'ë':
               filtered.append('e');
               break;
            case 'î':
            case 'ï':
               filtered.append('i');
               break;
            case 'ô':
            case 'ö':
               filtered.append('o');
               break;
            case 'ù':
            case 'û':
            case 'ü':
               filtered.append('u');
               break;
            // more characters would come here
            default:
               filtered.append(c);
         }
      }
      char[] newChars = new char[filtered.length()];
      filtered.getChars(0,filtered.length(),newChars,0);
      super.characters(newChars,0,filtered.length());
   }
}

package com.psol.xslist;

import java.io.*;
import javax.xml.transform.*;
import javax.xml.transform.sax.*;
import javax.xml.transform.stream.*;

public class Console
{
   public static void main(String[] args)
   {
      try
      {
         if(args.length < 3)
         {
            System.out.println("java com.psol.xslist.Console " +
                               "input.xml stylesheet.xsl output.txt");
            return;
         }
         Xml2Text xml2Text =
            new Xml2Text(new PrintWriter(new FileWriter(args[2])));
         WhitespaceFilter whitespaceFilter = new WhitespaceFilter();
         whitespaceFilter.setContentHandler(xml2Text);
         AsciiFilter asciiFilter = new AsciiFilter();
         asciiFilter.setContentHandler(whitespaceFilter);
         TransformerFactory factory = TransformerFactory.newInstance();
         Transformer transformer =
            factory.newTransformer(new StreamSource(new File(args[1])));
         transformer.transform(new StreamSource(new File(args[0])),
                               new SAXResult(asciiFilter));
      }
      catch(IOException e)
      {
         System.err.println(e.getMessage());
      }
      catch(TransformerException e)
      {
         System.err.println(e.getMessage());
      }
   }
}