XMLReader.java

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/*
    Calimero - A library for KNX network access
    Copyright (C) 2006-2008 B. Malinowsky

    This program is free software; you can redistribute it and/or 
    modify it under the terms of the GNU General Public License 
    as published by the Free Software Foundation; either version 2 
    of the License, or at your option any later version. 
 
    This program is distributed in the hope that it will be useful, 
    but WITHOUT ANY WARRANTY; without even the implied warranty of 
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
    GNU General Public License for more details. 
 
    You should have received a copy of the GNU General Public License 
    along with this program; if not, write to the Free Software 
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA. 
 
    Linking this library statically or dynamically with other modules is 
    making a combined work based on this library. Thus, the terms and 
    conditions of the GNU General Public License cover the whole 
    combination. 
 
    As a special exception, the copyright holders of this library give you 
    permission to link this library with independent modules to produce an 
    executable, regardless of the license terms of these independent 
    modules, and to copy and distribute the resulting executable under terms 
    of your choice, provided that you also meet, for each linked independent 
    module, the terms and conditions of the license of that module. An 
    independent module is a module which is not derived from or based on 
    this library. If you modify this library, you may extend this exception 
    to your version of the library, but you are not obligated to do so. If 
    you do not wish to do so, delete this exception statement from your 
    version. 
*/

package tuwien.auto.calimero.xml;

import java.io.Reader;

/**
 * XML reader interface for pull based reading of XML documents.
 * <p>
 * The reader only does non-validating processing, and resolves predefined XML entities.
 * <br>
 * This interface does not support XML namespaces for now, and has no methods for setting
 * and requesting XML reader features/properties.<br>
 * A reader based on pull parsing style only reads a little piece of a document at once,
 * waiting for the user application to request the next chunk of data. So the application
 * controls the progress of reading a XML document. The reader does not create nor
 * maintain a representation of the entire document for the user (like a model parser
 * would).
 * <p>
 * XML reader implementations don't need to be thread safe.
 * 
 * @author B. Malinowsky
 */
public interface XMLReader
{
	// The XML reader was using the
	// Extensible Markup Language (XML) 1.0 (Fourth Edition)
	// W3C Recommendation 16 August 2006, edited in place 29 September 2006,
	// but the current implementation status of the default reader is done only
	// up to give necessary support to handle Calimero XML stuff and not more.
	// If support for the XML schema for ETS configuration data is added,
	// maybe i will have a more in depth look to complete the one or other part.

	/** No input specified. */
	int NO_INPUT = 0;
	/** Start of XML document. */
	int START_DOC = 1;
	/** End of XML document. */
	int END_DOC = 2;
	/** Start of XML tag. */
	int START_TAG = 3;
	/** End of XML tag. */
	int END_TAG = 4;
	/**
	 * Character data of an element.
	 * <p>
	 * This position identifier is especially important on mixed content in an element.<br>
	 * (Definition: An element type has mixed content when elements of that type may
	 * contain character data, optionally interspersed with child elements.)<br>
	 * So this position only occurs between {@link #START_TAG} and {@link #END_TAG}.
	 * Anyway, usually there is no mixed content and {@link #complete(Element)} will be
	 * used after a START_TAG to read all character data into the supplied current
	 * element.
	 */
	int CHAR_DATA = 5;

	/**
	 * Sets the input source for this XML reader.
	 * <p>
	 * If this XML reader was already closed, setting a new input has no effect.
	 * 
	 * @param input a reader with input, like obtained from
	 *        {@link EntityResolver#getInputReader(java.io.InputStream)}
	 * @param close <code>true</code> if the specified input reader should be closed on
	 *        {@link #close()}, <code>false</code> to leave it open
	 */
	void setInput(Reader input, boolean close);

	/**
	 * Reads to the next XML element tag, a CDATA section or character data.
	 * <p>
	 * The logical position returned by this method can also be obtained with
	 * {@link #getPosition()}.<br>
	 * Comments and processing instructions can be ignored, i.e. skipped on reading.
	 * 
	 * @return the current logical position after reading
	 * @throws KNXMLException on read error or a not well-formed XML document
	 */
	int read() throws KNXMLException;

	/**
	 * Reads until end of element <code>e</code>.
	 * <p>
	 * All gathered relevant information is stored into <code>e</code>.
	 * 
	 * @param e the element to be completed
	 * @throws KNXMLException if document is not well-formed, e.g. end of input or end-tag
	 *         of parent element was reached before end of specified element
	 */
	void complete(Element e) throws KNXMLException;

	/**
	 * Returns the current element read with the last invocation of {@link #read()}.
	 * <p>
	 * 
	 * @return current element or <code>null</code> if no element is available
	 */
	Element getCurrent();

	/**
	 * Returns the current logical position in a XML document for this XML reader.
	 * <p>
	 * The position is given with constants like {@link #START_DOC} or similar. If no
	 * input was set or the reader is closed, {@link #NO_INPUT} is returned.
	 * 
	 * @return the logical position in the document
	 */
	int getPosition();

	/**
	 * Returns the line number for the current position in a XML input source processed by
	 * this XML reader.
	 * <p>
	 * On no input source, or before an input source is first read, 0 is returned.
	 * 
	 * @return line number, or 0 if no line number is available
	 */
	int getLineNumber();

	/**
	 * Closes this XML reader.
	 * <p>
	 * If this XML reader is already closed, no action is performed. If for an input
	 * source was specified to get closed on invocation of this method, it is closed first
	 * (calling {@link Reader#close()}.
	 * 
	 * @throws KNXMLException
	 */
	void close() throws KNXMLException;
}