Copyright (c) 2004, 2011 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
    Philippe Ombredanne (pombredanne@nexb.com) - bug 125367
/*******************************************************************************
 * Copyright (c) 2004, 2011 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     Philippe Ombredanne (pombredanne@nexb.com) - bug 125367
 *******************************************************************************/
package org.eclipse.ant.internal.core.contentDescriber;

import java.io.IOException;
import java.io.StringReader;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.eclipse.ant.internal.core.IAntCoreConstants;
import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.SAXNotRecognizedException;
import org.xml.sax.SAXNotSupportedException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.DefaultHandler;

An xml event handler for detecting the project top-level element in an Ant buildfile. Also records whether a default attribute is present for the
project and if any target or some other typical ant elements are present. There are still cases where we could ignore a valid ant buildfile though.
Since:
3.1/**
 * An xml event handler for detecting the project top-level element in an Ant buildfile. Also records whether a default attribute is present for the
 * project and if any target or some other typical ant elements are present. There are still cases where we could ignore a valid ant buildfile though.
 * 
 * @since 3.1
 */
public final class AntHandler extends DefaultHandler {
	
An exception indicating that the parsing should stop.
Since:
3.1/**
	 * An exception indicating that the parsing should stop.
	 * 
	 * @since 3.1
	 */
	private class StopParsingException extends SAXException {
		
All serializable objects should have a stable serialVersionUID
/**
		 * All serializable objects should have a stable serialVersionUID
		 */
		private static final long serialVersionUID = 1L;

		
Constructs an instance of StopParsingException with a null detail message.
/**
		 * Constructs an instance of <code>StopParsingException</code> with a <code>null</code> detail message.
		 */
		public StopParsingException() {
			super((String) null);
		}
	}

	private static final String PROJECT = "project"; //$NON-NLS-1$
	private static final String TARGET = "target"; //$NON-NLS-1$
	private static final String MACRODEF = "macrodef"; //$NON-NLS-1$
	private static final String TASKDEF = "taskdef"; //$NON-NLS-1$
	private static final String TYPEDEF = "typedef"; //$NON-NLS-1$
	private static final String PROPERTY = "property"; //$NON-NLS-1$
	private static final String CLASSPATH = "classpath"; //$NON-NLS-1$
	private static final String PATH = "path"; //$NON-NLS-1$
	private static final String IMPORT = "import"; //$NON-NLS-1$

	
This is the name of the top-level element found in the XML file. This member variable is null unless the file has been parsed
successful to the point of finding the top-level element.
/**
	 * This is the name of the top-level element found in the XML file. This member variable is <code>null</code> unless the file has been parsed
	 * successful to the point of finding the top-level element.
	 */
	private String fTopElementFound = null;
	private SAXParserFactory fFactory;

	private boolean fDefaultAttributeFound = false;
	private boolean fTargetFound = false;
	private boolean fAntElementFound = false;

	private int fLevel = -1;

	
Creates a new SAX parser for use within this instance.
Throws:
ParserConfigurationException – 
            If a parser of the given configuration cannot be created.
SAXException – 
            If something in general goes wrong when creating the parser.
Returns:
The newly created parser./**
	 * Creates a new SAX parser for use within this instance.
	 * 
	 * @return The newly created parser.
	 * @throws ParserConfigurationException
	 *             If a parser of the given configuration cannot be created.
	 * @throws SAXException
	 *             If something in general goes wrong when creating the parser.
	 */
	private final SAXParser createParser(SAXParserFactory parserFactory) throws ParserConfigurationException, SAXException, SAXNotRecognizedException, SAXNotSupportedException {
		// Initialize the parser.
		final SAXParser parser = parserFactory.newSAXParser();
		final XMLReader reader = parser.getXMLReader();
		// disable DTD validation (bug 63625)
		try {
			// be sure validation is "off" or the feature to ignore DTD's will not apply
			reader.setFeature("http://xml.org/sax/features/validation", false); //$NON-NLS-1$
			reader.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false); //$NON-NLS-1$
		}
		catch (SAXNotRecognizedException e) {
			// not a big deal if the parser does not recognize the features
		}
		catch (SAXNotSupportedException e) {
			// not a big deal if the parser does not support the features
		}
		return parser;
	}

	private SAXParserFactory getFactory() {
		synchronized (this) {
			if (fFactory != null) {
				return fFactory;
			}
			fFactory = SAXParserFactory.newInstance();
			fFactory.setNamespaceAware(true);
		}
		return fFactory;
	}

	protected boolean parseContents(InputSource contents) throws IOException, ParserConfigurationException, SAXException {
		// Parse the file into we have what we need (or an error occurs).
		try {
			fFactory = getFactory();
			if (fFactory == null) {
				return false;
			}
			final SAXParser parser = createParser(fFactory);
			// to support external entities specified as relative URIs (see bug 63298)
			contents.setSystemId("/"); //$NON-NLS-1$
			parser.parse(contents, this);
		}
		catch (StopParsingException e) {
			// Abort the parsing normally. Fall through...
		}
		return true;
	}

	/*
	 * Resolve external entity definitions to an empty string. This is to speed up processing of files with external DTDs. Not resolving the contents
	 * of the DTD is ok, as only the System ID of the DTD declaration is used.
	 * 
	 * @see org.xml.sax.helpers.DefaultHandler#resolveEntity(java.lang.String, java.lang.String)
	 */
	@Override
	public InputSource resolveEntity(String publicId, String systemId) throws SAXException {
		return new InputSource(new StringReader(IAntCoreConstants.EMPTY_STRING));
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.xml.sax.ContentHandler#startElement(java.lang.String, java.lang.String, java.lang.String, org.xml.sax.Attributes)
	 */
	@Override
	public final void startElement(final String uri, final String elementName, final String qualifiedName, final Attributes attributes) throws SAXException {
		fLevel++;
		if (fTopElementFound == null) {
			fTopElementFound = elementName;
			if (!hasRootProjectElement()) {
				throw new StopParsingException();
			}
			if (attributes != null) {
				fDefaultAttributeFound = attributes.getValue(IAntCoreConstants.DEFAULT) != null;
				if (fDefaultAttributeFound) {
					throw new StopParsingException();
				}
			}
		}
		if (fLevel == 1 && TARGET.equals(elementName)) {
			fTargetFound = true;
			throw new StopParsingException();
		}

		// top level Ant elements
		if (fLevel == 1
				&& (MACRODEF.equals(elementName) || TASKDEF.equals(elementName) || TYPEDEF.equals(elementName) || PROPERTY.equals(elementName)
						|| CLASSPATH.equals(elementName) || PATH.equals(elementName) || IMPORT.equals(elementName))) {
			fAntElementFound = true;
			throw new StopParsingException();
		}
	}

	/*
	 * (non-Javadoc)
	 * 
	 * @see org.xml.sax.ContentHandler#endElement(java.lang.String, java.lang.String, java.lang.String)
	 */
	@Override
	public void endElement(String uri, String localName, String qName) throws SAXException {
		super.endElement(uri, localName, qName);
		fLevel--;
	}

	protected boolean hasProjectDefaultAttribute() {
		return fDefaultAttributeFound;
	}

	protected boolean hasRootProjectElement() {
		return PROJECT.equals(fTopElementFound);
	}

	protected boolean hasTargetElement() {
		return fTargetFound;
	}

	protected boolean hasAntElement() {
		return fAntElementFound;
	}
}