// XMLWriter.java - serialize an XML document.
   // Written by David Megginson, david@megginson.com
   // NO WARRANTY! This class is in the public domain.
   
   // $Id:XMLWriter.java 378 2007-01-24 01:18:35Z mrohrmoser $
   
   package com.megginson.sax;
   
   import java.io.IOException;
  import java.io.OutputStreamWriter;
  import java.io.Writer;
  import java.util.Enumeration;
  import java.util.Hashtable;
  
  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;
  
  /**
   * 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(&quot;foo&quot;);
   * </pre>
   * 
   * <p>
   * is equivalent to the regular SAX2 ContentHandler method
   * </p>
   * 
   * <pre>
   * w.startElement(&quot;&quot;, &quot;foo&quot;, &quot;&quot;, 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(&quot;greeting&quot;);
   * w.characters(&quot;Hello, world!&quot;);
   * w.endElement(&quot;greeting&quot;);
   * w.endDocument();
   * </pre>
   * 
   * <p>
   * The resulting document will look like this:
   * </p>
   * 
   * <pre>
   *                 &lt;?xml version=&quot;1.0&quot; standalone=&quot;yes&quot;?&gt;
   *                
   *                 &lt;greeting&gt;Hello, world!&lt;/greeting&gt;
   * </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(&quot;greeting&quot;, &quot;Hello, world!&quot;);
   * 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(&quot;item&quot;, &quot;1&quot;);
  * w.dataElement(&quot;item&quot;, &quot;2&quot;);
  * w.dataElement(&quot;item&quot;, &quot;3&quot;);
  * </pre>
  * 
  * <p>
  * you will end up with
  * </p>
  * 
  * <pre>
  *                 &lt;item&gt;1&lt;/item&gt;&lt;item&gt;3&lt;/item&gt;&lt;item&gt;3&lt;/item&gt;
  * </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(&quot;http://www.foo.com/ns/&quot;, &quot;foo&quot;);
  * w.endDocument();
  * </pre>
  * 
  * <p>
  * The resulting document will look like this:
  * </p>
  * 
  * <pre>
  *                 &lt;?xml version=&quot;1.0&quot; standalone=&quot;yes&quot;?&gt;
  *                
  *                 &lt;_NS1:foo xmlns:_NS1=&quot;http://www.foo.com/ns/&quot;/&gt;
  * </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(&quot;http://www.foo.com/ns/&quot;, &quot;foo&quot;);
  * w.startDocument();
  * w.emptyElement(&quot;http://www.foo.com/ns/&quot;, &quot;foo&quot;);
  * w.endDocument();
  * </pre>
  * 
  * <p>
  * The resulting document will look like this:
  * </p>
  * 
  * <pre>
  *                 &lt;?xml version=&quot;1.0&quot; standalone=&quot;yes&quot;?&gt;
  *                
  *                 &lt;foo:foo xmlns:foo=&quot;http://www.foo.com/ns/&quot;/&gt;
  * </pre>
  * 
  * <p>
  * The default Namespace simply uses an empty string as the prefix:
  * </p>
  * 
  * <pre>
  * w.setPrefix(&quot;http://www.foo.com/ns/&quot;, &quot;&quot;);
  * w.startDocument();
  * w.emptyElement(&quot;http://www.foo.com/ns/&quot;, &quot;foo&quot;);
  * w.endDocument();
  * </pre>
  * 
  * <p>
  * The resulting document will look like this:
  * </p>
  * 
  * <pre>
  *                 &lt;?xml version=&quot;1.0&quot; standalone=&quot;yes&quot;?&gt;
  *                
  *                 &lt;foo xmlns=&quot;http://www.foo.com/ns/&quot;/&gt;
  * </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=&quot;1.0&quot; standalone=&quot;yes&quot;?&gt;
  *                
  *                 &lt;rdf:RDF xmlns:rdf=&quot;http://www.w3.org/1999/02/22-rdf-syntax-ns#&quot;&gt;
  *                  &lt;rdf:Description about=&quot;http://www.foo.com/ids/books/12345&quot;&gt;
  *                   &lt;dc:title xmlns:dc=&quot;http://www.purl.org/dc/&quot;&gt;A Dark Night&lt;/dc:title&gt;
  *                   &lt;dc:creator xmlns:dc=&quot;http://www.purl.org/dc/&quot;&gt;Jane Smith&lt;/dc:title&gt;
  *                   &lt;dc:date xmlns:dc=&quot;http://www.purl.org/dc/&quot;&gt;2000-09-09&lt;/dc:title&gt;
  *                  &lt;/rdf:Description&gt;
  *                 &lt;/rdf:RDF&gt;
  * </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(&quot;http://www.purl.org/dc/&quot;);
  * </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=&quot;1.0&quot; standalone=&quot;yes&quot;?&gt;
  *                
  *                 &lt;rdf:RDF xmlns:rdf=&quot;http://www.w3.org/1999/02/22-rdf-syntax-ns#&quot;
  *                             xmlns:dc=&quot;http://www.purl.org/dc/&quot;&gt;
  *                  &lt;rdf:Description about=&quot;http://www.foo.com/ids/books/12345&quot;&gt;
  *                   &lt;dc:title&gt;A Dark Night&lt;/dc:title&gt;
  *                   &lt;dc:creator&gt;Jane Smith&lt;/dc:title&gt;
  *                   &lt;dc:date&gt;2000-09-09&lt;/dc:title&gt;
  *                  &lt;/rdf:Description&gt;
  *                 &lt;/rdf:RDF&gt;
  * </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
  */
 class XMLWriter extends XMLFilterImpl {
 
 	// //////////////////////////////////////////////////////////////////
 	// Constructors.
 	// //////////////////////////////////////////////////////////////////
 
 	private Hashtable doneDeclTable;
 
 	private int elementLevel = 0;
 
 	private final Attributes EMPTY_ATTS = new AttributesImpl();
 
 	private Hashtable forcedDeclTable;
 
 	private NamespaceSupport nsSupport;
 
 	// //////////////////////////////////////////////////////////////////
 	// Public methods.
 	// //////////////////////////////////////////////////////////////////
 
 	private Writer output;
 
 	private int prefixCounter = 0;
 
 	private Hashtable prefixTable;
 
 	/**
 	 * 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(final 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(final 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(final XMLReader xmlreader, final Writer writer) {
 		super(xmlreader);
 		init(writer);
 	}
 
 	// //////////////////////////////////////////////////////////////////
 	// Methods from org.xml.sax.ContentHandler.
 	// //////////////////////////////////////////////////////////////////
 
 	/**
 	 * 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 len
 	 *            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
 	 */
 	@Override
 	public void characters(final char ch[], final int start, final int len)
 			throws SAXException {
 		writeEsc(ch, start, len, false);
 		super.characters(ch, start, len);
 	}
 
 	/**
 	 * 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(final String data) throws SAXException {
 		final char ch[] = data.toCharArray();
 		this.characters(ch, 0, ch.length);
 	}
 
 	/**
 	 * 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(final String localName, final String content)
 			throws SAXException {
 		this.dataElement("", localName, "", EMPTY_ATTS, content);
 	}
 
 	/**
 	 * 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(final String uri, final String localName,
 			final String content) throws SAXException {
 		this.dataElement(uri, localName, "", EMPTY_ATTS, content);
 	}
 
 	/**
 	 * 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(final String uri, final String localName,
 			final String qName, final Attributes atts, final String content)
 			throws SAXException {
 		this.startElement(uri, localName, qName, atts);
 		this.characters(content);
 		this.endElement(uri, localName, qName);
 	}
 
 	/**
 	 * 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).
 	 * @return ???
 	 */
 	private String doPrefix(final String uri, final String qName,
 			boolean isElement) {
 		final 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)) {
 			final 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;
 	}
 
 	/**
 	 * 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(final String localName) throws SAXException {
 		this.emptyElement("", localName, "", EMPTY_ATTS);
 	}
 
 	// //////////////////////////////////////////////////////////////////
 	// Additional markup.
 	// //////////////////////////////////////////////////////////////////
 
 	/**
 	 * 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(final String uri, final String localName)
 			throws SAXException {
 		this.emptyElement(uri, localName, "", EMPTY_ATTS);
 	}
 
 	// //////////////////////////////////////////////////////////////////
 	// Convenience methods.
 	// //////////////////////////////////////////////////////////////////
 
 	/**
 	 * 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(String)} and an
 	 * {@link #endElement(String) } 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(String, String, String, Attributes)
 	 * @see #endElement(String, String, String)
 	 */
 	public void emptyElement(final String uri, final String localName,
 			final String qName, final Attributes atts) throws SAXException {
 		nsSupport.pushContext();
 		this.write('<');
 		writeName(uri, localName, qName, true);
 		writeAttributes(atts);
 		if (elementLevel == 1)
 			forceNSDecls();
 		writeNSDecls();
 		this.write("/>");
 		super.startElement(uri, localName, qName, atts);
 		super.endElement(uri, localName, qName);
 	}
 
 	/**
 	 * 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
 	 */
 	@Override
 	public void endDocument() throws SAXException {
 		this.write('\n');
 		super.endDocument();
 		try {
 			flush();
 		} catch (final IOException e) {
 			throw new SAXException(e);
 		}
 	}
 
 	/**
 	 * 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(final String localName) throws SAXException {
 		this.endElement("", localName, "");
 	}
 
 	/**
 	 * 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(final String uri, final String localName)
 			throws SAXException {
 		this.endElement(uri, localName, "");
 	}
 
 	/**
 	 * 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
 	 */
 	@Override
 	public void endElement(final String uri, final String localName,
 			final String qName) throws SAXException {
 		this.write("</");
 		writeName(uri, localName, qName, true);
 		this.write('>');
 		if (elementLevel == 1)
 			this.write('\n');
 		super.endElement(uri, localName, qName);
 		nsSupport.popContext();
 		elementLevel--;
 	}
 
 	/**
 	 * 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>
 	 * 
 	 * @throws IOException
 	 * @see #reset
 	 */
 	public void flush() throws IOException {
 		output.flush();
 	}
 
 	/**
 	 * 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(final 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(final String uri, final String prefix) {
 		setPrefix(uri, prefix);
 		this.forceNSDecl(uri);
 	}
 
 	/**
 	 * 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() {
 		final Enumeration prefixes = forcedDeclTable.keys();
 		while (prefixes.hasMoreElements()) {
 			final String prefix = (String) prefixes.nextElement();
 			doPrefix(prefix, null, true);
 		}
 	}
 
 	/**
 	 * 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(final String uri) {
 		return (String) prefixTable.get(uri);
 	}
 
 	// //////////////////////////////////////////////////////////////////
 	// Internal methods.
 	// //////////////////////////////////////////////////////////////////
 
 	/**
 	 * 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
 	 */
 	@Override
 	public void ignorableWhitespace(final char ch[], final int start,
 			final int length) throws SAXException {
 		writeEsc(ch, start, length, false);
 		super.ignorableWhitespace(ch, start, length);
 	}
 
 	/**
 	 * 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(final Writer writer) {
 		setOutput(writer);
 		nsSupport = new NamespaceSupport();
 		prefixTable = new Hashtable();
 		forcedDeclTable = new Hashtable();
 		doneDeclTable = new Hashtable();
 	}
 
 	/**
 	 * 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
 	 */
 	@Override
 	public void processingInstruction(final String target, final String data)
 			throws SAXException {
 		this.write("<?");
 		this.write(target);
 		this.write(' ');
 		this.write(data);
 		this.write("?>");
 		if (elementLevel < 1)
 			this.write('\n');
 		super.processingInstruction(target, data);
 	}
 
 	/**
 	 * 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();
 	}
 
 	/**
 	 * Set a new output destination for the document.
 	 * 
 	 * @param writer
 	 *            The output destination, or null to use standard output.
 	 * @see #flush
 	 */
 	public void setOutput(final 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(final String uri, final String prefix) {
 		prefixTable.put(uri, prefix);
 	}
 
 	/**
 	 * 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
 	 */
 	@Override
 	public void startDocument() throws SAXException {
 		reset();
 		this.write("<?xml version=\"1.0\" standalone=\"yes\"?>\n\n");
 		super.startDocument();
 	}
 
 	/**
 	 * 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(final String localName) throws SAXException {
 		this.startElement("", localName, "", EMPTY_ATTS);
 	}
 
 	// //////////////////////////////////////////////////////////////////
 	// Constants.
 	// //////////////////////////////////////////////////////////////////
 
 	/**
 	 * 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(final String uri, final String localName)
 			throws SAXException {
 		this.startElement(uri, localName, "", EMPTY_ATTS);
 	}
 
 	// //////////////////////////////////////////////////////////////////
 	// Internal state.
 	// //////////////////////////////////////////////////////////////////
 
 	/**
 	 * 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
 	 */
 	@Override
 	public void startElement(final String uri, final String localName,
 			final String qName, final Attributes atts) throws SAXException {
 		elementLevel++;
 		nsSupport.pushContext();
 		this.write('<');
 		writeName(uri, localName, qName, true);
 		writeAttributes(atts);
 		if (elementLevel == 1)
 			forceNSDecls();
 		writeNSDecls();
 		this.write('>');
 		super.startElement(uri, localName, qName, atts);
 	}
 
 	/**
 	 * 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(final char c) throws SAXException {
 		try {
 			output.write(c);
 		} catch (final 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(final String s) throws SAXException {
 		try {
 			output.write(s);
 		} catch (final 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 SAXException
 	 *                If there is an error writing the attribute list, this
 	 *                method will throw an IOException wrapped in a
 	 *                SAXException.
 	 */
 	private void writeAttributes(final Attributes atts) throws SAXException {
 		final int len = atts.getLength();
 		for (int i = 0; i < len; i++) {
 			final char ch[] = atts.getValue(i).toCharArray();
 			this.write(' ');
 			writeName(atts.getURI(i), atts.getLocalName(i), atts.getQName(i),
 					false);
 			this.write("=\"");
 			writeEsc(ch, 0, ch.length, true);
 			this.write('"');
 		}
 	}
 
 	/**
 	 * 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 SAXException
 	 *                If there is an error writing the characters, this method
 	 *                will throw an IOException wrapped in a SAXException.
 	 */
 	private void writeEsc(final char ch[], final int start, final int length,
 			final boolean isAttVal) throws SAXException {
 		for (int i = start; i < start + length; i++)
 			switch (ch[i]) {
 			case '&':
 				this.write("&amp;");
 				break;
 			case '<':
 				this.write("&lt;");
 				break;
 			case '>':
 				this.write("&gt;");
 				break;
 			case '\"':
 				if (isAttVal)
 					this.write("&quot;");
 				else
 					this.write('\"');
 				break;
 			default:
 				if (ch[i] > '\u007f') {
 					this.write("&#");
 					this.write(Integer.toString(ch[i]));
 					this.write(';');
 				} else
 					this.write(ch[i]);
 			}
 	}
 
 	/**
 	 * 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(final String uri, final String localName,
 			final String qName, final boolean isElement) throws SAXException {
 		final String prefix = doPrefix(uri, qName, isElement);
 		if (prefix != null && !"".equals(prefix)) {
 			this.write(prefix);
 			this.write(':');
 		}
 		this.write(localName);
 	}
 
 	/**
 	 * 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 {
 		final Enumeration prefixes = nsSupport.getDeclaredPrefixes();
 		while (prefixes.hasMoreElements()) {
 			final String prefix = (String) prefixes.nextElement();
 			String uri = nsSupport.getURI(prefix);
 			if (uri == null)
 				uri = "";
 			final char ch[] = uri.toCharArray();
 			this.write(' ');
 			if ("".equals(prefix))
 				this.write("xmlns=\"");
 			else {
 				this.write("xmlns:");
 				this.write(prefix);
 				this.write("=\"");
 			}
 			writeEsc(ch, 0, ch.length, true);
 			this.write('\"');
 		}
 	}
 
 }
 
 // end of XMLWriter.java