cowan/tagsoup/XMLWriter.java

// XMLWriter.java - serialize an XML document.
// Written by David Megginson, david@megginson.com
// and placed by him into the public domain.
// Extensively modified by John Cowan for TagSoup.
// TagSoup is licensed under the Apache License,
// Version 2.0.  You may obtain a copy of this license at
// http://www.apache.org/licenses/LICENSE-2.0 .  You may also have
// additional legal rights not granted by this license.
//
// TagSoup is distributed in the hope that it will be useful, but
// unless required by applicable law or agreed to in writing, TagSoup
// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS
// OF ANY KIND, either express or implied; not even the implied warranty
// of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

package org.ccil.cowan.tagsoup;

import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.Properties;

import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.AttributesImpl;
import org.xml.sax.helpers.NamespaceSupport;
import org.xml.sax.helpers.XMLFilterImpl;
import org.xml.sax.ext.LexicalHandler;


/**
 * Filter to write an XML document from a SAX event stream.
 *
 * <p>This class can be used by itself or as part of a SAX event
 * stream: it takes as input a series of SAX2 ContentHandler
 * events and uses the information in those events to write
 * an XML document.  Since this class is a filter, it can also
 * pass the events on down a filter chain for further processing
 * (you can use the XMLWriter to take a snapshot of the current
 * state at any point in a filter chain), and it can be
 * used directly as a ContentHandler for a SAX2 XMLReader.</p>
 *
 * <p>The client creates a document by invoking the methods for
 * standard SAX2 events, always beginning with the
 * {@link #startDocument startDocument} method and ending with
 * the {@link #endDocument endDocument} method.  There are convenience
 * methods provided so that clients to not have to create empty
 * attribute lists or provide empty strings as parameters; for
 * example, the method invocation</p>
 *
 * <pre>
 * w.startElement("foo");
 * </pre>
 *
 * <p>is equivalent to the regular SAX2 ContentHandler method</p>
 *
 * <pre>
 * w.startElement("", "foo", "", new AttributesImpl());
 * </pre>
 *
 * <p>Except that it is more efficient because it does not allocate
 * a new empty attribute list each time.  The following code will send
 * a simple XML document to standard output:</p>
 *
 * <pre>
 * XMLWriter w = new XMLWriter();
 *
 * w.startDocument();
 * w.startElement("greeting");
 * w.characters("Hello, world!");
 * w.endElement("greeting");
 * w.endDocument();
 * </pre>
 *
 * <p>The resulting document will look like this:</p>
 *
 * <pre>
 * &lt;?xml version="1.0" standalone="yes"?>
 *
 * &lt;greeting>Hello, world!&lt;/greeting>
 * </pre>
 *
 * <p>In fact, there is an even simpler convenience method,
 * <var>dataElement</var>, designed for writing elements that
 * contain only character data, so the code to generate the
 * document could be shortened to</p>
 *
 * <pre>
 * XMLWriter w = new XMLWriter();
 *
 * w.startDocument();
 * w.dataElement("greeting", "Hello, world!");
 * w.endDocument();
 * </pre>
 *
 * <h2>Whitespace</h2>
 *
 * <p>According to the XML Recommendation, <em>all</em> whitespace
 * in an XML document is potentially significant to an application,
 * so this class never adds newlines or indentation.  If you
 * insert three elements in a row, as in</p>
 *
 * <pre>
 * w.dataElement("item", "1");
 * w.dataElement("item", "2");
 * w.dataElement("item", "3");
 * </pre>
 *
 * <p>you will end up with</p>
 *
 * <pre>
 * &lt;item>1&lt;/item>&lt;item>3&lt;/item>&lt;item>3&lt;/item>
 * </pre>
 *
 * <p>You need to invoke one of the <var>characters</var> methods
 * explicitly to add newlines or indentation.  Alternatively, you
 * can use {@link com.megginson.sax.DataWriter DataWriter}, which
 * is derived from this class -- it is optimized for writing
 * purely data-oriented (or field-oriented) XML, and does automatic
 * linebreaks and indentation (but does not support mixed content
 * properly).</p>
 *
 *
 * <h2>Namespace Support</h2>
 *
 * <p>The writer contains extensive support for XML Namespaces, so that
 * a client application does not have to keep track of prefixes and
 * supply <var>xmlns</var> attributes.  By default, the XML writer will
 * generate Namespace declarations in the form _NS1, _NS2, etc., wherever
 * they are needed, as in the following example:</p>
 *
 * <pre>
 * w.startDocument();
 * w.emptyElement("http://www.foo.com/ns/", "foo");
 * w.endDocument();
 * </pre>
 *
 * <p>The resulting document will look like this:</p>
 *
 * <pre>
 * &lt;?xml version="1.0" standalone="yes"?>
 *
 * &lt;_NS1:foo xmlns:_NS1="http://www.foo.com/ns/"/>
 * </pre>
 *
 * <p>In many cases, document authors will prefer to choose their
 * own prefixes rather than using the (ugly) default names.  The
 * XML writer allows two methods for selecting prefixes:</p>
 *
 * <ol>
 * <li>the qualified name</li>
 * <li>the {@link #setPrefix setPrefix} method.</li>
 * </ol>
 *
 * <p>Whenever the XML writer finds a new Namespace URI, it checks
 * to see if a qualified (prefixed) name is also available; if so
 * it attempts to use the name's prefix (as long as the prefix is
 * not already in use for another Namespace URI).</p>
 *
 * <p>Before writing a document, the client can also pre-map a prefix
 * to a Namespace URI with the setPrefix method:</p>
 *
 * <pre>
 * w.setPrefix("http://www.foo.com/ns/", "foo");
 * w.startDocument();
 * w.emptyElement("http://www.foo.com/ns/", "foo");
 * w.endDocument();
 * </pre>
 *
 * <p>The resulting document will look like this:</p>
 *
 * <pre>
 * &lt;?xml version="1.0" standalone="yes"?>
 *
 * &lt;foo:foo xmlns:foo="http://www.foo.com/ns/"/>
 * </pre>
 *
 * <p>The default Namespace simply uses an empty string as the prefix:</p>
 *
 * <pre>
 * w.setPrefix("http://www.foo.com/ns/", "");
 * w.startDocument();
 * w.emptyElement("http://www.foo.com/ns/", "foo");
 * w.endDocument();
 * </pre>
 *
 * <p>The resulting document will look like this:</p>
 *
 * <pre>
 * &lt;?xml version="1.0" standalone="yes"?>
 *
 * &lt;foo xmlns="http://www.foo.com/ns/"/>
 * </pre>
 *
 * <p>By default, the XML writer will not declare a Namespace until
 * it is actually used.  Sometimes, this approach will create
 * a large number of Namespace declarations, as in the following
 * example:</p>
 *
 * <pre>
 * &lt;xml version="1.0" standalone="yes"?>
 *
 * &lt;rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
 *  &lt;rdf:Description about="http://www.foo.com/ids/books/12345">
 *   &lt;dc:title xmlns:dc="http://www.purl.org/dc/">A Dark Night&lt;/dc:title>
 *   &lt;dc:creator xmlns:dc="http://www.purl.org/dc/">Jane Smith&lt;/dc:title>
 *   &lt;dc:date xmlns:dc="http://www.purl.org/dc/">2000-09-09&lt;/dc:title>
 *  &lt;/rdf:Description>
 * &lt;/rdf:RDF>
 * </pre>
 *
 * <p>The "rdf" prefix is declared only once, because the RDF Namespace
 * is used by the root element and can be inherited by all of its
 * descendants; the "dc" prefix, on the other hand, is declared three
 * times, because no higher element uses the Namespace.  To solve this
 * problem, you can instruct the XML writer to predeclare Namespaces
 * on the root element even if they are not used there:</p>
 *
 * <pre>
 * w.forceNSDecl("http://www.purl.org/dc/");
 * </pre>
 *
 * <p>Now, the "dc" prefix will be declared on the root element even
 * though it's not needed there, and can be inherited by its
 * descendants:</p>
 *
 * <pre>
 * &lt;xml version="1.0" standalone="yes"?>
 *
 * &lt;rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
 *             xmlns:dc="http://www.purl.org/dc/">
 *  &lt;rdf:Description about="http://www.foo.com/ids/books/12345">
 *   &lt;dc:title>A Dark Night&lt;/dc:title>
 *   &lt;dc:creator>Jane Smith&lt;/dc:title>
 *   &lt;dc:date>2000-09-09&lt;/dc:title>
 *  &lt;/rdf:Description>
 * &lt;/rdf:RDF>
 * </pre>
 *
 * <p>This approach is also useful for declaring Namespace prefixes
 * that be used by qualified names appearing in attribute values or
 * character data.</p>
 *
 * @author David Megginson, david@megginson.com
 * @version 0.2
 * @see org.xml.sax.XMLFilter
 * @see org.xml.sax.ContentHandler
 */
public class XMLWriter extends XMLFilterImpl implements LexicalHandler
{


    ////////////////////////////////////////////////////////////////////
    // Constructors.
    ////////////////////////////////////////////////////////////////////


    /**
     * Create a new XML writer.
     *
     * <p>Write to standard output.</p>
     */
    public XMLWriter ()
    {
        init(null);
    }


    /**
     * Create a new XML writer.
     *
     * <p>Write to the writer provided.</p>
     *
     * @param writer The output destination, or null to use standard
     *        output.
     */
    public XMLWriter (Writer writer)
    {
        init(writer);
    }


    /**
     * Create a new XML writer.
     *
     * <p>Use the specified XML reader as the parent.</p>
     *
     * @param xmlreader The parent in the filter chain, or null
     *        for no parent.
     */
    public XMLWriter (XMLReader xmlreader)
    {
        super(xmlreader);
        init(null);
    }


    /**
     * Create a new XML writer.
     *
     * <p>Use the specified XML reader as the parent, and write
     * to the specified writer.</p>
     *
     * @param xmlreader The parent in the filter chain, or null
     *        for no parent.
     * @param writer The output destination, or null to use standard
     *        output.
     */
    public XMLWriter (XMLReader xmlreader, Writer writer)
    {
        super(xmlreader);
        init(writer);
    }


    /**
     * Internal initialization method.
     *
     * <p>All of the public constructors invoke this method.
     *
     * @param writer The output destination, or null to use
     *        standard output.
     */
    private void init (Writer writer)
    {
        setOutput(writer);
        nsSupport = new NamespaceSupport();
        prefixTable = new Hashtable();
        forcedDeclTable = new Hashtable();
        doneDeclTable = new Hashtable();
        outputProperties = new Properties();
    }


    ////////////////////////////////////////////////////////////////////
    // Public methods.
    ////////////////////////////////////////////////////////////////////


    /**
     * Reset the writer.
     *
     * <p>This method is especially useful if the writer throws an
     * exception before it is finished, and you want to reuse the
     * writer for a new document.  It is usually a good idea to
     * invoke {@link #flush flush} before resetting the writer,
     * to make sure that no output is lost.</p>
     *
     * <p>This method is invoked automatically by the
     * {@link #startDocument startDocument} method before writing
     * a new document.</p>
     *
     * <p><strong>Note:</strong> this method will <em>not</em>
     * clear the prefix or URI information in the writer or
     * the selected output writer.</p>
     *
     * @see #flush
     */
    public void reset ()
    {
        elementLevel = 0;
        prefixCounter = 0;
        nsSupport.reset();
    }


    /**
     * Flush the output.
     *
     * <p>This method flushes the output stream.  It is especially useful
     * when you need to make certain that the entire document has
     * been written to output but do not want to close the output
     * stream.</p>
     *
     * <p>This method is invoked automatically by the
     * {@link #endDocument endDocument} method after writing a
     * document.</p>
     *
     * @see #reset
     */
    public void flush ()
        throws IOException
    {
        output.flush();
    }


    /**
     * Set a new output destination for the document.
     *
     * @param writer The output destination, or null to use
     *        standard output.
     * @return The current output writer.
     * @see #flush
     */
    public void setOutput (Writer writer)
    {
        if (writer == null) {
            output = new OutputStreamWriter(System.out);
        } else {
            output = writer;
        }
    }


    /**
     * Specify a preferred prefix for a Namespace URI.
     *
     * <p>Note that this method does not actually force the Namespace
     * to be declared; to do that, use the {@link
     * #forceNSDecl(java.lang.String) forceNSDecl} method as well.</p>
     *
     * @param uri The Namespace URI.
     * @param prefix The preferred prefix, or "" to select
     *        the default Namespace.
     * @see #getPrefix
     * @see #forceNSDecl(java.lang.String)
     * @see #forceNSDecl(java.lang.String,java.lang.String)
     */
    public void setPrefix (String uri, String prefix)
    {
        prefixTable.put(uri, prefix);
    }


    /**
     * Get the current or preferred prefix for a Namespace URI.
     *
     * @param uri The Namespace URI.
     * @return The preferred prefix, or "" for the default Namespace.
     * @see #setPrefix
     */
    public String getPrefix (String uri)
    {
        return (String)prefixTable.get(uri);
    }


    /**
     * Force a Namespace to be declared on the root element.
     *
     * <p>By default, the XMLWriter will declare only the Namespaces
     * needed for an element; as a result, a Namespace may be
     * declared many places in a document if it is not used on the
     * root element.</p>
     *
     * <p>This method forces a Namespace to be declared on the root
     * element even if it is not used there, and reduces the number
     * of xmlns attributes in the document.</p>
     *
     * @param uri The Namespace URI to declare.
     * @see #forceNSDecl(java.lang.String,java.lang.String)
     * @see #setPrefix
     */
    public void forceNSDecl (String uri)
    {
        forcedDeclTable.put(uri, Boolean.TRUE);
    }


    /**
     * Force a Namespace declaration with a preferred prefix.
     *
     * <p>This is a convenience method that invokes {@link
     * #setPrefix setPrefix} then {@link #forceNSDecl(java.lang.String)
     * forceNSDecl}.</p>
     *
     * @param uri The Namespace URI to declare on the root element.
     * @param prefix The preferred prefix for the Namespace, or ""
     *        for the default Namespace.
     * @see #setPrefix
     * @see #forceNSDecl(java.lang.String)
     */
    public void forceNSDecl (String uri, String prefix)
    {
        setPrefix(uri, prefix);
        forceNSDecl(uri);
    }


    ////////////////////////////////////////////////////////////////////
    // Methods from org.xml.sax.ContentHandler.
    ////////////////////////////////////////////////////////////////////


    /**
     * Write the XML declaration at the beginning of the document.
     *
     * Pass the event on down the filter chain for further processing.
     *
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the XML declaration, or if a handler further down
     *            the filter chain raises an exception.
     * @see org.xml.sax.ContentHandler#startDocument
     */
    public void startDocument ()
        throws SAXException
    {
        reset();
        if (!("yes".equals(outputProperties.getProperty(OMIT_XML_DECLARATION, "no")))) {
            write("<?xml");
            if (version == null) {
                write(" version=\"1.0\"");
            } else {
                write(" version=\"");
                write(version);
                write("\"");
            }
            if (outputEncoding != null && outputEncoding != "") {
                write(" encoding=\"");
                write(outputEncoding);
                write("\"");
            }
            if (standalone == null) {
                write(" standalone=\"yes\"?>\n");
            } else {
                write(" standalone=\"");
                write(standalone);
                write("\"");
            }
        }
        super.startDocument();
    }


    /**
     * Write a newline at the end of the document.
     *
     * Pass the event on down the filter chain for further processing.
     *
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the newline, or if a handler further down
     *            the filter chain raises an exception.
     * @see org.xml.sax.ContentHandler#endDocument
     */
    public void endDocument ()
        throws SAXException
    {
        write('\n');
        super.endDocument();
        try {
            flush();
        } catch (IOException e) {
            throw new SAXException(e);
        }
    }


    /**
     * Write a start tag.
     *
     * Pass the event on down the filter chain for further processing.
     *
     * @param uri The Namespace URI, or the empty string if none
     *        is available.
     * @param localName The element's local (unprefixed) name (required).
     * @param qName The element's qualified (prefixed) name, or the
     *        empty string is none is available.  This method will
     *        use the qName as a template for generating a prefix
     *        if necessary, but it is not guaranteed to use the
     *        same qName.
     * @param atts The element's attribute list (must not be null).
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the start tag, or if a handler further down
     *            the filter chain raises an exception.
     * @see org.xml.sax.ContentHandler#startElement
     */
    public void startElement (String uri, String localName,
                              String qName, Attributes atts)
        throws SAXException
    {
        elementLevel++;
        nsSupport.pushContext();
	if (forceDTD && !hasOutputDTD) startDTD(localName == null ? qName : localName, "", "");
        write('<');
        writeName(uri, localName, qName, true);
        writeAttributes(atts);
        if (elementLevel == 1) {
            forceNSDecls();
        }
        writeNSDecls();
        write('>');
//	System.out.println("%%%% startElement [" + qName + "] htmlMode = " + htmlMode);
	if (htmlMode && (qName.equals("script") || qName.equals("style"))) {
                cdataElement = true;
//		System.out.println("%%%% CDATA element");
                }
        super.startElement(uri, localName, qName, atts);
    }


    /**
     * Write an end tag.
     *
     * Pass the event on down the filter chain for further processing.
     *
     * @param uri The Namespace URI, or the empty string if none
     *        is available.
     * @param localName The element's local (unprefixed) name (required).
     * @param qName The element's qualified (prefixed) name, or the
     *        empty string is none is available.  This method will
     *        use the qName as a template for generating a prefix
     *        if necessary, but it is not guaranteed to use the
     *        same qName.
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the end tag, or if a handler further down
     *            the filter chain raises an exception.
     * @see org.xml.sax.ContentHandler#endElement
     */
    public void endElement (String uri, String localName, String qName)
        throws SAXException
    {
	if (!(htmlMode &&
            (uri.equals("http://www.w3.org/1999/xhtml") ||
		uri.equals("")) &&
            (qName.equals("area") || qName.equals("base") ||
            qName.equals("basefont") || qName.equals("br") ||
            qName.equals("col") || qName.equals("frame") ||
            qName.equals("hr") || qName.equals("img") ||
            qName.equals("input") || qName.equals("isindex") ||
            qName.equals("link") || qName.equals("meta") ||
            qName.equals("param")))) {
                write("</");
                writeName(uri, localName, qName, true);
                write('>');
            }
        if (elementLevel == 1) {
            write('\n');
        }
        cdataElement = false;
        super.endElement(uri, localName, qName);
        nsSupport.popContext();
        elementLevel--;
    }


    /**
     * Write character data.
     *
     * Pass the event on down the filter chain for further processing.
     *
     * @param ch The array of characters to write.
     * @param start The starting position in the array.
     * @param length The number of characters to write.
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the characters, or if a handler further down
     *            the filter chain raises an exception.
     * @see org.xml.sax.ContentHandler#characters
     */
    public void characters (char ch[], int start, int len)
        throws SAXException
    {
        if (!cdataElement) {
          writeEsc(ch, start, len, false);
          }
        else {
          for (int i = start; i < start + len; i++) {
            write(ch[i]);
            }
          }
        super.characters(ch, start, len);
    }


    /**
     * Write ignorable whitespace.
     *
     * Pass the event on down the filter chain for further processing.
     *
     * @param ch The array of characters to write.
     * @param start The starting position in the array.
     * @param length The number of characters to write.
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the whitespace, or if a handler further down
     *            the filter chain raises an exception.
     * @see org.xml.sax.ContentHandler#ignorableWhitespace
     */
    public void ignorableWhitespace (char ch[], int start, int length)
        throws SAXException
    {
        writeEsc(ch, start, length, false);
        super.ignorableWhitespace(ch, start, length);
    }


    /**
     * Write a processing instruction.
     *
     * Pass the event on down the filter chain for further processing.
     *
     * @param target The PI target.
     * @param data The PI data.
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the PI, or if a handler further down
     *            the filter chain raises an exception.
     * @see org.xml.sax.ContentHandler#processingInstruction
     */
    public void processingInstruction (String target, String data)
        throws SAXException
    {
        write("<?");
        write(target);
        write(' ');
        write(data);
        write("?>");
        if (elementLevel < 1) {
            write('\n');
        }
        super.processingInstruction(target, data);
    }


    ////////////////////////////////////////////////////////////////////
    // Additional markup.
    ////////////////////////////////////////////////////////////////////

    /**
     * Write an empty element.
     *
     * This method writes an empty element tag rather than a start tag
     * followed by an end tag.  Both a {@link #startElement
     * startElement} and an {@link #endElement endElement} event will
     * be passed on down the filter chain.
     *
     * @param uri The element's Namespace URI, or the empty string
     *        if the element has no Namespace or if Namespace
     *        processing is not being performed.
     * @param localName The element's local name (without prefix).  This
     *        parameter must be provided.
     * @param qName The element's qualified name (with prefix), or
     *        the empty string if none is available.  This parameter
     *        is strictly advisory: the writer may or may not use
     *        the prefix attached.
     * @param atts The element's attribute list.
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the empty tag, or if a handler further down
     *            the filter chain raises an exception.
     * @see #startElement
     * @see #endElement
     */
    public void emptyElement (String uri, String localName,
                              String qName, Attributes atts)
        throws SAXException
    {
        nsSupport.pushContext();
        write('<');
        writeName(uri, localName, qName, true);
        writeAttributes(atts);
        if (elementLevel == 1) {
            forceNSDecls();
        }
        writeNSDecls();
        write("/>");
        super.startElement(uri, localName, qName, atts);
        super.endElement(uri, localName, qName);
    }


    ////////////////////////////////////////////////////////////////////
    // Convenience methods.
    ////////////////////////////////////////////////////////////////////


    /**
     * Start a new element without a qname or attributes.
     *
     * <p>This method will provide a default empty attribute
     * list and an empty string for the qualified name.
     * It invokes {@link
     * #startElement(String, String, String, Attributes)}
     * directly.</p>
     *
     * @param uri The element's Namespace URI.
     * @param localName The element's local name.
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the start tag, or if a handler further down
     *            the filter chain raises an exception.
     * @see #startElement(String, String, String, Attributes)
     */
    public void startElement (String uri, String localName)
        throws SAXException
    {
        startElement(uri, localName, "", EMPTY_ATTS);
    }


    /**
     * Start a new element without a qname, attributes or a Namespace URI.
     *
     * <p>This method will provide an empty string for the
     * Namespace URI, and empty string for the qualified name,
     * and a default empty attribute list. It invokes
     * #startElement(String, String, String, Attributes)}
     * directly.</p>
     *
     * @param localName The element's local name.
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the start tag, or if a handler further down
     *            the filter chain raises an exception.
     * @see #startElement(String, String, String, Attributes)
     */
    public void startElement (String localName)
        throws SAXException
    {
        startElement("", localName, "", EMPTY_ATTS);
    }


    /**
     * End an element without a qname.
     *
     * <p>This method will supply an empty string for the qName.
     * It invokes {@link #endElement(String, String, String)}
     * directly.</p>
     *
     * @param uri The element's Namespace URI.
     * @param localName The element's local name.
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the end tag, or if a handler further down
     *            the filter chain raises an exception.
     * @see #endElement(String, String, String)
     */
    public void endElement (String uri, String localName)
        throws SAXException
    {
        endElement(uri, localName, "");
    }


    /**
     * End an element without a Namespace URI or qname.
     *
     * <p>This method will supply an empty string for the qName
     * and an empty string for the Namespace URI.
     * It invokes {@link #endElement(String, String, String)}
     * directly.</p>
     *
     * @param localName The element's local name.
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the end tag, or if a handler further down
     *            the filter chain raises an exception.
     * @see #endElement(String, String, String)
     */
    public void endElement (String localName)
        throws SAXException
    {
        endElement("", localName, "");
    }


    /**
     * Add an empty element without a qname or attributes.
     *
     * <p>This method will supply an empty string for the qname
     * and an empty attribute list.  It invokes
     * {@link #emptyElement(String, String, String, Attributes)}
     * directly.</p>
     *
     * @param uri The element's Namespace URI.
     * @param localName The element's local name.
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the empty tag, or if a handler further down
     *            the filter chain raises an exception.
     * @see #emptyElement(String, String, String, Attributes)
     */
    public void emptyElement (String uri, String localName)
        throws SAXException
    {
        emptyElement(uri, localName, "", EMPTY_ATTS);
    }


    /**
     * Add an empty element without a Namespace URI, qname or attributes.
     *
     * <p>This method will supply an empty string for the qname,
     * and empty string for the Namespace URI, and an empty
     * attribute list.  It invokes
     * {@link #emptyElement(String, String, String, Attributes)}
     * directly.</p>
     *
     * @param localName The element's local name.
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the empty tag, or if a handler further down
     *            the filter chain raises an exception.
     * @see #emptyElement(String, String, String, Attributes)
     */
    public void emptyElement (String localName)
        throws SAXException
    {
        emptyElement("", localName, "", EMPTY_ATTS);
    }


    /**
     * Write an element with character data content.
     *
     * <p>This is a convenience method to write a complete element
     * with character data content, including the start tag
     * and end tag.</p>
     *
     * <p>This method invokes
     * {@link #startElement(String, String, String, Attributes)},
     * followed by
     * {@link #characters(String)}, followed by
     * {@link #endElement(String, String, String)}.</p>
     *
     * @param uri The element's Namespace URI.
     * @param localName The element's local name.
     * @param qName The element's default qualified name.
     * @param atts The element's attributes.
     * @param content The character data content.
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the empty tag, or if a handler further down
     *            the filter chain raises an exception.
     * @see #startElement(String, String, String, Attributes)
     * @see #characters(String)
     * @see #endElement(String, String, String)
     */
    public void dataElement (String uri, String localName,
                             String qName, Attributes atts,
                             String content)
        throws SAXException
    {
        startElement(uri, localName, qName, atts);
        characters(content);
        endElement(uri, localName, qName);
    }


    /**
     * Write an element with character data content but no attributes.
     *
     * <p>This is a convenience method to write a complete element
     * with character data content, including the start tag
     * and end tag.  This method provides an empty string
     * for the qname and an empty attribute list.</p>
     *
     * <p>This method invokes
     * {@link #startElement(String, String, String, Attributes)},
     * followed by
     * {@link #characters(String)}, followed by
     * {@link #endElement(String, String, String)}.</p>
     *
     * @param uri The element's Namespace URI.
     * @param localName The element's local name.
     * @param content The character data content.
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the empty tag, or if a handler further down
     *            the filter chain raises an exception.
     * @see #startElement(String, String, String, Attributes)
     * @see #characters(String)
     * @see #endElement(String, String, String)
     */
    public void dataElement (String uri, String localName, String content)
        throws SAXException
    {
        dataElement(uri, localName, "", EMPTY_ATTS, content);
    }


    /**
     * Write an element with character data content but no attributes or Namespace URI.
     *
     * <p>This is a convenience method to write a complete element
     * with character data content, including the start tag
     * and end tag.  The method provides an empty string for the
     * Namespace URI, and empty string for the qualified name,
     * and an empty attribute list.</p>
     *
     * <p>This method invokes
     * {@link #startElement(String, String, String, Attributes)},
     * followed by
     * {@link #characters(String)}, followed by
     * {@link #endElement(String, String, String)}.</p>
     *
     * @param localName The element's local name.
     * @param content The character data content.
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the empty tag, or if a handler further down
     *            the filter chain raises an exception.
     * @see #startElement(String, String, String, Attributes)
     * @see #characters(String)
     * @see #endElement(String, String, String)
     */
    public void dataElement (String localName, String content)
        throws SAXException
    {
        dataElement("", localName, "", EMPTY_ATTS, content);
    }


    /**
     * Write a string of character data, with XML escaping.
     *
     * <p>This is a convenience method that takes an XML
     * String, converts it to a character array, then invokes
     * {@link #characters(char[], int, int)}.</p>
     *
     * @param data The character data.
     * @exception org.xml.sax.SAXException If there is an error
     *            writing the string, or if a handler further down
     *            the filter chain raises an exception.
     * @see #characters(char[], int, int)
     */
    public void characters (String data)
        throws SAXException
    {
        char ch[] = data.toCharArray();
        characters(ch, 0, ch.length);
    }


    ////////////////////////////////////////////////////////////////////
    // Internal methods.
    ////////////////////////////////////////////////////////////////////


    /**
     * Force all Namespaces to be declared.
     *
     * This method is used on the root element to ensure that
     * the predeclared Namespaces all appear.
     */
    private void forceNSDecls ()
    {
        Enumeration prefixes = forcedDeclTable.keys();
        while (prefixes.hasMoreElements()) {
            String prefix = (String)prefixes.nextElement();
            doPrefix(prefix, null, true);
        }
    }


    /**
     * Determine the prefix for an element or attribute name.
     *
     * TODO: this method probably needs some cleanup.
     *
     * @param uri The Namespace URI.
     * @param qName The qualified name (optional); this will be used
     *        to indicate the preferred prefix if none is currently
     *        bound.
     * @param isElement true if this is an element name, false
     *        if it is an attribute name (which cannot use the
     *        default Namespace).
     */
    private String doPrefix (String uri, String qName, boolean isElement)
    {
        String defaultNS = nsSupport.getURI("");
        if ("".equals(uri)) {
            if (isElement && defaultNS != null)
                nsSupport.declarePrefix("", "");
            return null;
        }
        String prefix;
        if (isElement && defaultNS != null && uri.equals(defaultNS)) {
            prefix = "";
        } else {
            prefix = nsSupport.getPrefix(uri);
        }
        if (prefix != null) {
            return prefix;
        }
        prefix = (String) doneDeclTable.get(uri);
        if (prefix != null &&
            ((!isElement || defaultNS != null) &&
             "".equals(prefix) || nsSupport.getURI(prefix) != null)) {
            prefix = null;
        }
        if (prefix == null) {
            prefix = (String) prefixTable.get(uri);
            if (prefix != null &&
                ((!isElement || defaultNS != null) &&
                 "".equals(prefix) || nsSupport.getURI(prefix) != null)) {
                prefix = null;
            }
        }
        if (prefix == null && qName != null && !"".equals(qName)) {
            int i = qName.indexOf(':');
            if (i == -1) {
                if (isElement && defaultNS == null) {
                    prefix = "";
                }
            } else {
                prefix = qName.substring(0, i);
            }
        }
        for (;
             prefix == null || nsSupport.getURI(prefix) != null;
             prefix = "__NS" + ++prefixCounter)
            ;
        nsSupport.declarePrefix(prefix, uri);
        doneDeclTable.put(uri, prefix);
        return prefix;
    }


    /**
     * Write a raw character.
     *
     * @param c The character to write.
     * @exception org.xml.sax.SAXException If there is an error writing
     *            the character, this method will throw an IOException
     *            wrapped in a SAXException.
     */
    private void write (char c)
        throws SAXException
    {
        try {
            output.write(c);
        } catch (IOException e) {
            throw new SAXException(e);
        }
    }


    /**
     * Write a raw string.
     *
     * @param s
     * @exception org.xml.sax.SAXException If there is an error writing
     *            the string, this method will throw an IOException
     *            wrapped in a SAXException
     */
    private void write (String s)
    throws SAXException
    {
        try {
            output.write(s);
        } catch (IOException e) {
            throw new SAXException(e);
        }
    }


    /**
     * Write out an attribute list, escaping values.
     *
     * The names will have prefixes added to them.
     *
     * @param atts The attribute list to write.
     * @exception org.xml.SAXException If there is an error writing
     *            the attribute list, this method will throw an
     *            IOException wrapped in a SAXException.
     */
    private void writeAttributes (Attributes atts)
        throws SAXException
    {
        int len = atts.getLength();
        for (int i = 0; i < len; i++) {
            char ch[] = atts.getValue(i).toCharArray();
            write(' ');
            writeName(atts.getURI(i), atts.getLocalName(i),
                      atts.getQName(i), false);
            if (htmlMode &&
                booleanAttribute(atts.getLocalName(i), atts.getQName(i), atts.getValue(i))) break;
            write("=\"");
            writeEsc(ch, 0, ch.length, true);
            write('"');
        }
    }


    private String[] booleans = {"checked", "compact", "declare", "defer",
                                 "disabled", "ismap", "multiple",
                                 "nohref", "noresize", "noshade",
                                 "nowrap", "readonly", "selected"};

    // Return true if the attribute is an HTML boolean from the above list.
    private boolean booleanAttribute (String localName, String qName, String value)
    {
        String name = localName;
        if (name == null) {
            int i = qName.indexOf(':');
            if (i != -1) name = qName.substring(i + 1, qName.length());
        }
        if (!name.equals(value)) return false;
        for (int j = 0; j < booleans.length; j++) {
            if (name.equals(booleans[j])) return true;
            }
        return false;
    }

    /**
     * Write an array of data characters with escaping.
     *
     * @param ch The array of characters.
     * @param start The starting position.
     * @param length The number of characters to use.
     * @param isAttVal true if this is an attribute value literal.
     * @exception org.xml.SAXException If there is an error writing
     *            the characters, this method will throw an
     *            IOException wrapped in a SAXException.
     */
    private void writeEsc (char ch[], int start,
                             int length, boolean isAttVal)
        throws SAXException
    {
        for (int i = start; i < start + length; i++) {
            switch (ch[i]) {
            case '&':
                write("&amp;");
                break;
            case '<':
                write("&lt;");
                break;
            case '>':
                write("&gt;");
                break;
            case '\"':
                if (isAttVal) {
                    write("&quot;");
                } else {
                    write('\"');
                }
                break;
            default:
                if (!unicodeMode && ch[i] > '\u007f') {
                    write("&#");
                    write(Integer.toString(ch[i]));
                    write(';');
                } else {
                    write(ch[i]);
                }
            }
        }
    }


    /**
     * Write out the list of Namespace declarations.
     *
     * @exception org.xml.sax.SAXException This method will throw
     *            an IOException wrapped in a SAXException if
     *            there is an error writing the Namespace
     *            declarations.
     */
    private void writeNSDecls ()
        throws SAXException
    {
        Enumeration prefixes = nsSupport.getDeclaredPrefixes();
        while (prefixes.hasMoreElements()) {
            String prefix = (String) prefixes.nextElement();
            String uri = nsSupport.getURI(prefix);
            if (uri == null) {
                uri = "";
            }
            char ch[] = uri.toCharArray();
            write(' ');
            if ("".equals(prefix)) {
                write("xmlns=\"");
            } else {
                write("xmlns:");
                write(prefix);
                write("=\"");
            }
            writeEsc(ch, 0, ch.length, true);
            write('\"');
        }
    }


    /**
     * Write an element or attribute name.
     *
     * @param uri The Namespace URI.
     * @param localName The local name.
     * @param qName The prefixed name, if available, or the empty string.
     * @param isElement true if this is an element name, false if it
     *        is an attribute name.
     * @exception org.xml.sax.SAXException This method will throw an
     *            IOException wrapped in a SAXException if there is
     *            an error writing the name.
     */
    private void writeName (String uri, String localName,
                              String qName, boolean isElement)
        throws SAXException
    {
        String prefix = doPrefix(uri, qName, isElement);
        if (prefix != null && !"".equals(prefix)) {
            write(prefix);
            write(':');
        }
        if (localName != null && !"".equals(localName)) {
            write(localName);
        } else {
            int i = qName.indexOf(':');
            write(qName.substring(i + 1, qName.length()));
        }
    }


    ////////////////////////////////////////////////////////////////////
    // Default LexicalHandler implementation
    ////////////////////////////////////////////////////////////////////

    public void comment(char[] ch, int start, int length) throws SAXException
    {
        write("<!--");
        for (int i = start; i < start + length; i++) {
                write(ch[i]);
                if (ch[i] == '-' && i + 1 <= start + length && ch[i+1] == '-')
                        write(' ');
                }
        write("-->");
    }

    public void endCDATA() throws SAXException { }
    public void endDTD() throws SAXException { }
    public void endEntity(String name) throws SAXException { }
    public void startCDATA() throws SAXException { }
    public void startDTD(String name, String publicid, String systemid) throws SAXException {
        if (name == null) return;               // can't cope
	if (hasOutputDTD) return;		// only one DTD
	hasOutputDTD = true;
        write("<!DOCTYPE ");
        write(name);
        if (systemid == null) systemid = "";
	if (overrideSystem != null) systemid = overrideSystem;
        char sysquote = (systemid.indexOf('"') != -1) ? '\'': '"';
	if (overridePublic != null) publicid = overridePublic;
        if (!(publicid == null || "".equals(publicid))) {
                char pubquote = (publicid.indexOf('"') != -1) ? '\'': '"';
                write(" PUBLIC ");
                write(pubquote);
                write(publicid);
                write(pubquote);
                write(' ');
                }
        else {
                write(" SYSTEM ");
                }
        write(sysquote);
        write(systemid);
        write(sysquote);
        write(">\n");
        }

    public void startEntity(String name) throws SAXException { }


    ////////////////////////////////////////////////////////////////////
    // Output properties
    ////////////////////////////////////////////////////////////////////

    public String getOutputProperty(String key) {
        return outputProperties.getProperty(key);
    }

    public void setOutputProperty(String key, String value) {
        outputProperties.setProperty(key, value);
//	System.out.println("%%%% key = [" + key + "] value = [" + value +"]");
        if (key.equals(ENCODING)) {
            outputEncoding = value;
            unicodeMode = value.substring(0, 3).equalsIgnoreCase("utf");
//                System.out.println("%%%% unicodeMode = " + unicodeMode);
	}
	else if (key.equals(METHOD)) {
		htmlMode = value.equals("html");
	}
	else if (key.equals(DOCTYPE_PUBLIC)) {
		overridePublic = value;
		forceDTD = true;
		}
	else if (key.equals(DOCTYPE_SYSTEM)) {
		overrideSystem = value;
		forceDTD = true;
		}
	else if (key.equals(VERSION)) {
		version = value;
		}
	else if (key.equals(STANDALONE)) {
		standalone = value;
		}
//	System.out.println("%%%% htmlMode = " + htmlMode);
    }


    ////////////////////////////////////////////////////////////////////
    // Constants.
    ////////////////////////////////////////////////////////////////////

    private final Attributes EMPTY_ATTS = new AttributesImpl();
    public static final String CDATA_SECTION_ELEMENTS =
        "cdata-section-elements";
    public static final String DOCTYPE_PUBLIC = "doctype-public";
    public static final String DOCTYPE_SYSTEM = "doctype-system";
    public static final String ENCODING = "encoding";
    public static final String INDENT = "indent";  // currently ignored
    public static final String MEDIA_TYPE = "media-type";  // currently ignored
    public static final String METHOD = "method";  // currently html or xml
    public static final String OMIT_XML_DECLARATION = "omit-xml-declaration";
    public static final String STANDALONE = "standalone";  // currently ignored
    public static final String VERSION = "version";


    ////////////////////////////////////////////////////////////////////
    // Internal state.
    ////////////////////////////////////////////////////////////////////

    private Hashtable prefixTable;
    private Hashtable forcedDeclTable;
    private Hashtable doneDeclTable;
    private int elementLevel = 0;
    private Writer output;
    private NamespaceSupport nsSupport;
    private int prefixCounter = 0;
    private Properties outputProperties;
    private boolean unicodeMode = false;
    private String outputEncoding = "";
    private boolean htmlMode = false;
    private boolean forceDTD = false;
    private boolean hasOutputDTD = false;
    private String overridePublic = null;
    private String overrideSystem = null;
    private String version = null;
    private String standalone = null;
    private boolean cdataElement = false;

}

// end of XMLWriter.java