com.topologi.diffx.xml.XMLIndenter Maven / Gradle / Ivy
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/*
* This file is part of the DiffX library.
*
* For licensing information please see the file license.txt included in the release.
* A copy of this licence can also be found at
* http://www.opensource.org/licenses/artistic-license-2.0.php
*/
package com.topologi.diffx.xml;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.Writer;
import java.util.Stack;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;
/**
* A class to indent automatically some XML data.
*
* Note: This implementation is not namespace aware, and will not handle entities other than
* &, <, > or ".
*
* @author Christophe Lauret - Allette Systems (Australia)
* @version 26 February 2005
*/
public final class XMLIndenter extends DefaultHandler implements ContentHandler {
/**
* The writer where the XML goes.
*/
private final PrintWriter writer;
// state attributes ---------------------------------------------------------------------------
/**
* The indentation level.
*/
private transient int indentLevel = 0;
/**
* The stack of states
*/
private transient Stack states = new Stack();
/**
* Element has neither text, nor children.
*/
private static final Integer EMPTY = new Integer(0);
/**
* Element has text.
*/
private static final Integer HAS_TEXT = new Integer(1);
/**
* Element has children.
*/
private static final Integer HAS_CHILDREN = new Integer(2);
/* ----------------------------------------- constructor --------------------------------------- */
/**
* Creates a new XML Indenter.
*
* @param w The writer to use.
*/
private XMLIndenter(Writer w) {
if (w instanceof PrintWriter) {
this.writer = (PrintWriter) w;
} else {
this.writer = new PrintWriter(w);
}
}
/* -------------------------------------- handler's methods ------------------------------------ */
/**
* {@inheritDoc}
*/
@Override
public void startElement(String uri, String localName, String qName, Attributes atts) {
// update the state of previous element
if (!this.states.empty()) {
if (this.states.pop().equals(EMPTY)) {
this.writer.println('>');
}
this.states.push(HAS_CHILDREN);
}
// always indent
for (int i = 0; i < this.indentLevel; i++) {
this.writer.print(" ");
}
// print XML data
this.writer.print('<' + qName);
for (int i = 0; i < atts.getLength(); i++) {
this.writer.print(' '+atts.getQName(i)+"=\""+atts.getValue(i)+'"');
}
// update attributes
this.indentLevel++;
this.states.push(EMPTY);
}
/**
* {@inheritDoc}
*/
@Override
public void endElement(String uri, String localName, String qName) {
this.indentLevel--;
Object state = this.states.pop();
if (EMPTY.equals(state)) {
this.writer.println("/>");
} else if (HAS_TEXT.equals(state)) {
this.writer.println("');
} else if (HAS_CHILDREN.equals(state)) {
for (int i = 0; i < this.indentLevel; i++) {
this.writer.print(" ");
}
this.writer.println("');
}
}
/**
* Prints the characters.
*
* {@inheritDoc}
*/
@Override
public void characters(char[] ch, int position, int offset) {
if (this.states.peek().equals(EMPTY)) {
this.states.pop();
this.writer.print('>');
this.states.push(HAS_TEXT);
}
this.writer.print(new String(ch, position, offset));
}
/**
* Does nothing.
*
* {@inheritDoc}
*/
@Override
public void ignorableWhitespace(char[] ch, int position, int offset) {
// do nothing.
}
/* ---------------------------------------- static methods ------------------------------------- */
/**
* Indents the given XML String.
*
* @param xml The XML string to indent
*
* @return The indented XML String.
*
* @throws IOException If an IOException occurs.
* @throws SAXException If the XML is not well-formed.
* @throws ParserConfigurationException If the parser could not be configured
*/
public static String indent(String xml)
throws SAXException, IOException, ParserConfigurationException {
Writer writer = new StringWriter();
Reader reader = new StringReader(xml);
indent(reader, writer);
return writer.toString();
}
/**
* Indents the given XML String.
*
* @param r A reader on XML data
* @param w A writer for the indented XML
*
* @throws IOException If an IOException occurs.
* @throws SAXException If the XML is not well-formed.
* @throws ParserConfigurationException If the parser could not be configured
*/
public static void indent(Reader r, Writer w)
throws SAXException, IOException, ParserConfigurationException {
// create the indenter
XMLIndenter indenter = new XMLIndenter(w);
// initialise the SAX framework
SAXParserFactory factory = SAXParserFactory.newInstance();
factory.setNamespaceAware(false);
factory.setValidating(false);
InputSource source = new InputSource(r);
// parse the XML
SAXParser parser = factory.newSAXParser();
parser.setProperty("http://xml.org/sax/features/external-general-entities", false);
parser.setProperty("http://xml.org/sax/features/external-parameter-entities", false);
parser.setProperty("http://apache.org/xml/features/disallow-doctype-decl", true);
XMLReader xmlreader = parser.getXMLReader();
xmlreader.setContentHandler(indenter);
xmlreader.parse(source);
}
/**
* Indents the given XML String.
*
* @param xml The XML string to indent
*
* @return The indented XML String or null if an error occurred.
*/
public static String indentSilent(String xml) {
try {
return indent(xml);
} catch (Exception ex) {
return null;
}
}
/**
* Indents the given XML String.
*
* This method does not throw any exception out of convenience, instead it returns a
* boolean value to indicate whether the XML indenting was performed succesfully.
*
* @param r A reader on XML data
* @param w A writer for the indented XML
*
* @return true if the operation was successful, false if an error
* occurred.
*/
public static boolean indentSilent(Reader r, Writer w) {
try {
indent(r, w);
return true;
} catch (Exception ex) {
return false;
}
}
}