IndentingXMLWriter.java

package edu.northwestern.at.utils.xml;

/*	Please see the license information at the end of this file. */

import java.io.*;
import java.util.*;

import com.megginson.sax.*;

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

import edu.northwestern.at.utils.*;

/**	XMLWriter which indents the output before each tag.
 *
 *	<p>
 *	This code assumes the XML is not currently indented.
 *	</p>
 */

public class IndentingXMLWriter extends XMLWriter
{
	/**	Number of spaces to indent each level of XML. */

	protected int indentStep	= 0;

	/**	Blanks for indentation. */

	protected char[] indents	= new char[ 0 ];

	/**	End of line character(s). */

 	protected char[] eol		= Env.LINE_SEPARATOR.toCharArray();

	/**	Stack which remembers if a tag has at least one child.
	 *
	 *	<p>
	 *	The start and end tags of an element with no children are
	 *	kept on the same line.
	 *	</p>
	 */

	protected QueueStack<Boolean> childStack	= new QueueStack<Boolean>();

	/**	Create indenting XML writer.
	 *
	 *	@param	xmlReader	The XML Reader to which this writer is attached.
	 *	@param	writer		The output writer to which to output the
	 *						indented XML.
	 */

    public IndentingXMLWriter
    (
    	XMLReader xmlReader ,
    	Writer writer
    )
    {
    	super( xmlReader , writer );
	}

    /**	Return the current indent step.
     *
     * @return	The number of indents in each indentation step.
     *			0 or less for no indentation.
     */

	public int getIndentStep()
	{
		return indentStep;
	}

    /**	Set the current indent step.
     *
     *	@param	indentStep	The new indent step (0 or less for no
     *						indentation).
     */

	public void setIndentStep( int indentStep )
	{
		this.indentStep = indentStep;

		if ( indentStep > 0 )
		{
			indents	= new char[ indentStep ];

			Arrays.fill( indents , ' ' );
		}
	}

	/**	Handle start of an XML element.
	  *
	  *	@param	uri			The XML element's URI.
	  *	@param	localName	The XML element's local name.
	  *	@param	qName		The XML element's qname.
	  *	@param	atts		The XML element's attributes.
	  */

	public void startElement
	(
		String uri ,
		String localName ,
		String qName ,
		Attributes atts
	)
		throws SAXException
	{
								//	Emit EOL before new element. */

		super.ignorableWhitespace( eol , 0 , eol.length );

								//	Indent this line based upon
								//	depth in XML tree.  The number
								//	of elements on the child stack
								//	provides the number of parents
								//	of this element, and the number
								//	of indentation blocks.
		if ( indentStep > 0 )
		{
			for ( int i = 0 ; i < childStack.size() ; i++ )
			{
				super.ignorableWhitespace( indents , 0 , indents.length );
			}
		}
								//	If this element has a parent,
								//	set the child stack value for the
								//	parent to true.

		if ( !childStack.isEmpty() )
		{
			childStack.pop();
			childStack.push( true );
		}
								//	Assume this element has no children.
								//	We update this if we find children
								//	later.

		childStack.push( false );

								//	Perform standard processing
								//	for this element.

		super.startElement( uri , localName , qName , atts );
	}

	/**	Handle end of an element.
	 *
	 *	@param	uri			The XML element's URI.
	 *	@param	localName	The XML element's local name.
	 *	@param	qName		The XML element's qname.
	 */

	public void endElement
	(
		String uri ,
		String localName ,
		String qName
	)
		throws SAXException
	{
									//	See if this element
									//	had any children.

		boolean hadChildElement = childStack.pop();

		if ( hadChildElement )
		{
									//	If so, emit EOL, and
									//	output indentation before
									//	the close tag.

			super.ignorableWhitespace( eol , 0 , eol.length );

			if ( indentStep > 0 )
			{
				for ( int i = 0 ; i < childStack.size(); i++ )
				{
					super.ignorableWhitespace( indents , 0 , indents.length );
				}
			}
		}
								//	Perform standard processing
								//	for this element.

		super.endElement( uri , localName , qName );
	}
}

/*
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All rights reserved.

Developed by:
   Academic and Research Technologies
   Northwestern University
   http://www.it.northwestern.edu/about/departments/at/

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obtaining a copy of this software and associated documentation
files (the "Software"), to deal with the Software without
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sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following
conditions:

    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimers.

    * Redistributions in binary form must reproduce the above
      copyright notice, this list of conditions and the following
      disclaimers in the documentation and/or other materials provided
      with the distribution.

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      Northwestern University, nor the names of its contributors may be
      used to endorse or promote products derived from this Software
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