// DataWriter.java - XML writer for data-oriented files.
package com.megginson.sax;
/* Please see the license information at the end of this file. */
import java.io.Writer;
import java.util.Stack;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
/**
* Write data- or field-oriented XML.
*
* <p>This filter pretty-prints field-oriented XML without mixed content.
* all added indentation and newlines will be passed on down
* the filter chain (if any).</p>
*
* <p>In general, all whitespace in an XML document is potentially
* significant, so a general-purpose XML writing tool like the
* {@link com.megginson.sax.XMLWriter XMLWriter} class cannot
* add newlines or indentation.</p>
*
* <p>There is, however, a large class of XML documents where information
* is strictly fielded: each element contains either character data
* or other elements, but not both. For this special case, it is possible
* for a writing tool to provide automatic indentation and newlines
* without requiring extra work from the user. Note that this class
* will likely not yield appropriate results for document-oriented
* XML like XHTML pages, which mix character data and elements together.</p>
*
* <p>This writer will automatically place each start tag on a new line,
* optionally indented if an indent step is provided (by default, there
* is no indentation). If an element contains other elements, the end
* tag will also appear on a new line with leading indentation. Consider,
* for example, the following code:</p>
*
* <pre>
* DataWriter w = new DataWriter();
*
* w.setIndentStep(2);
* w.startDocument();
* w.startElement("Person");
* w.dataElement("name", "Jane Smith");
* w.dataElement("date-of-birth", "1965-05-23");
* w.dataElement("citizenship", "US");
* w.endElement("Person");
* w.endDocument();
* </pre>
*
* <p>This code will produce the following document:</p>
*
* <pre>
* <?xml version="1.0" standalone="yes"?>
*
* <Person>
* <name>Jane Smith</name>
* <date-of-birth>1965-05-23</date-of-birth>
* <citizenship>US</citizenship>
* </Person>
* </pre>
*
* <p>This class inherits from {@link com.megginson.sax.XMLWriter
* XMLWriter}, and provides all of the same support for Namespaces.</p>
*
* @author David Megginson, david@megginson.com
* @version 0.2
* @see com.megginson.sax.XMLWriter
* <p>
* Use system platform end-of-line sequence instead of just \n.
* Use typed collections.
* Philip R. Burns. 2007/04/23 .
* </p>
*/
public class DataWriter extends XMLWriter
{
////////////////////////////////////////////////////////////////////
// Constructors.
////////////////////////////////////////////////////////////////////
/**
* Create a new data writer for standard output.
*/
public DataWriter ()
{
super();
}
/**
* Create a new data writer for standard output.
*
* <p>Use the XMLReader provided as the source of events.</p>
*
* @param xmlreader The parent in the filter chain.
*/
public DataWriter (XMLReader xmlreader)
{
super(xmlreader);
}
/**
* Create a new data writer for the specified output.
*
* @param writer The character stream where the XML document
* will be written.
*/
public DataWriter (Writer writer)
{
super(writer);
}
/**
* Create a new data writer for the specified output.
* <p>Use the XMLReader provided as the source of events.</p>
*
* @param xmlreader The parent in the filter chain.
* @param writer The character stream where the XML document
* will be written.
*/
public DataWriter (XMLReader xmlreader, Writer writer)
{
super(xmlreader, writer);
}
////////////////////////////////////////////////////////////////////
// Accessors and setters.
////////////////////////////////////////////////////////////////////
/**
* Return the current indent step.
*
* <p>Return the current indent step: each start tag will be
* indented by this number of spaces times the number of
* ancestors that the element has.</p>
*
* @return The number of spaces in each indentation step,
* or 0 or less for no indentation.
* @see #setIndentStep
*/
public int getIndentStep ()
{
return indentStep;
}
/**
* Set the current indent step.
*
* @param indentStep The new indent step (0 or less for no
* indentation).
* @see #getIndentStep
*/
public void setIndentStep (int indentStep)
{
this.indentStep = indentStep;
}
////////////////////////////////////////////////////////////////////
// Override methods from XMLWriter.
////////////////////////////////////////////////////////////////////
/**
* Reset the writer so that it can be reused.
*
* <p>This method is especially useful if the writer failed
* with an exception the last time through.</p>
*
* @see com.megginson.sax.XMLWriter#reset
*/
public void reset ()
{
depth = 0;
state = SEEN_NOTHING;
stateStack = new Stack<Object>();
super.reset();
}
/**
* Write a start tag.
*
* <p>Each tag will begin on a new line, and will be
* indented by the current indent step times the number
* of ancestors that the element has.</p>
*
* <p>The newline and indentation will be passed on down
* the filter chain through regular characters events.</p>
*
* @param uri The element's Namespace URI.
* @param localName The element's local name.
* @param qName The element's qualified (prefixed) name.
* @param atts The element's attribute list.
* @exception org.xml.sax.SAXException If there is an error
* writing the start tag, or if a filter further
* down the chain raises an exception.
* @see XMLWriter#startElement(String, String, String, Attributes)
*/
public void startElement (String uri, String localName,
String qName, Attributes atts)
throws SAXException
{
stateStack.push(SEEN_ELEMENT);
state = SEEN_NOTHING;
if (depth > 0) {
super.characters( LINE_SEPARATOR );
}
doIndent();
super.startElement(uri, localName, qName, atts);
depth++;
}
/**
* Write an end tag.
*
* <p>If the element has contained other elements, the tag
* will appear indented on a new line; otherwise, it will
* appear immediately following whatever came before.</p>
*
* <p>The newline and indentation will be passed on down
* the filter chain through regular characters events.</p>
*
* @param uri The element's Namespace URI.
* @param localName The element's local name.
* @param qName The element's qualified (prefixed) name.
* @exception org.xml.sax.SAXException If there is an error
* writing the end tag, or if a filter further
* down the chain raises an exception.
* @see XMLWriter#endElement(String, String, String)
*/
public void endElement (String uri, String localName, String qName)
throws SAXException
{
depth--;
if (state == SEEN_ELEMENT) {
super.characters( LINE_SEPARATOR );
doIndent();
}
super.endElement(uri, localName, qName);
state = stateStack.pop();
}
/**
* Write a empty element tag.
*
* <p>Each tag will appear on a new line, and will be
* indented by the current indent step times the number
* of ancestors that the element has.</p>
*
* <p>The newline and indentation will be passed on down
* the filter chain through regular characters events.</p>
*
* @param uri The element's Namespace URI.
* @param localName The element's local name.
* @param qName The element's qualified (prefixed) name.
* @param atts The element's attribute list.
* @exception org.xml.sax.SAXException If there is an error
* writing the empty tag, or if a filter further
* down the chain raises an exception.
* @see XMLWriter#emptyElement(String, String, String, Attributes)
*/
public void emptyElement (String uri, String localName,
String qName, Attributes atts)
throws SAXException
{
state = SEEN_ELEMENT;
if (depth > 0) {
super.characters( LINE_SEPARATOR );
}
doIndent();
super.emptyElement(uri, localName, qName, atts);
}
/**
* Write a sequence of characters.
*
* @param ch The characters to write.
* @param start The starting position in the array.
* @param length The number of characters to use.
* @exception org.xml.sax.SAXException If there is an error
* writing the characters, or if a filter further
* down the chain raises an exception.
* @see XMLWriter#characters(char[], int, int)
*/
public void characters (char ch[], int start, int length)
throws SAXException
{
state = SEEN_DATA;
super.characters(ch, start, length);
}
////////////////////////////////////////////////////////////////////
// Internal methods.
////////////////////////////////////////////////////////////////////
/**
* Print indentation for the current level.
*
* @exception org.xml.sax.SAXException If there is an error
* writing the indentation characters, or if a filter
* further down the chain raises an exception.
*/
private void doIndent ()
throws SAXException
{
if (indentStep > 0 && depth > 0) {
int n = indentStep * depth;
char ch[] = new char[n];
for (int i = 0; i < n; i++) {
ch[i] = ' ';
}
characters(ch, 0, n);
}
}
////////////////////////////////////////////////////////////////////
// Constants.
////////////////////////////////////////////////////////////////////
private final static Object SEEN_NOTHING = new Object();
private final static Object SEEN_ELEMENT = new Object();
private final static Object SEEN_DATA = new Object();
////////////////////////////////////////////////////////////////////
// Internal state.
////////////////////////////////////////////////////////////////////
private Object state = SEEN_NOTHING;
private Stack<Object> stateStack = new Stack<Object>();
private int indentStep = 0;
private int depth = 0;
}
// end of DataWriter.java
/*
All of this code has been placed into the public domain by
David Megginson. Therefore no license applies.
*/