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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code 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

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package java.beans;

import com.sun.beans.decoder.DocumentHandler;

import java.io.Closeable;

import java.io.InputStream;

import java.io.IOException;

import org.xml.sax.InputSource;

import org.xml.sax.helpers.DefaultHandler;

/**

 * The <code>XMLDecoder</code> class is used to read XML documents

 * created using the <code>XMLEncoder</code> and is used just like

 * the <code>ObjectInputStream</code>. For example, one can use

 * the following fragment to read the first object defined

 * in an XML document written by the <code>XMLEncoder</code>

 * class:

 * <pre>

 *       XMLDecoder d = new XMLDecoder(

 *                          new BufferedInputStream(

 *                              new FileInputStream("Test.xml")));

 *       Object result = d.readObject();

 *       d.close();

 * </pre>

 *

 *<p>

 * For more information you might also want to check out

 * <a

 href="http://java.sun.com/products/jfc/tsc/articles/persistence3">Long Term Persistence of JavaBeans Components: XML Schema</a>,

 * an article in <em>The Swing Connection.</em>

 * @see XMLEncoder

 * @see java.io.ObjectInputStream

 *

 * @since 1.4

 *

 * @author Philip Milne

 */

public class XMLDecoder implements AutoCloseable {

    private final DocumentHandler handler = new DocumentHandler();

    private final InputSource input;

    private Object owner;

    private Object[] array;

    private int index;

    /**

     * Creates a new input stream for reading archives

     * created by the <code>XMLEncoder</code> class.

     *

     * @param in The underlying stream.

     *

     * @see XMLEncoder#XMLEncoder(java.io.OutputStream)

     */

    public XMLDecoder(InputStream in) {

        this(in, null);

    }

    /**

     * Creates a new input stream for reading archives

     * created by the <code>XMLEncoder</code> class.

     *

     * @param in The underlying stream.

     * @param owner The owner of this stream.

     *

     */

    public XMLDecoder(InputStream in, Object owner) {

        this(in, owner, null);

    }

    /**

     * Creates a new input stream for reading archives

     * created by the <code>XMLEncoder</code> class.

     *

     * @param in the underlying stream.

     * @param owner the owner of this stream.

     * @param exceptionListener the exception handler for the stream;

     *        if <code>null</code> the default exception listener will be used.

     */

    public XMLDecoder(InputStream in, Object owner, ExceptionListener exceptionListener) {

        this(in, owner, exceptionListener, null);

    }

    /**

     * Creates a new input stream for reading archives

     * created by the <code>XMLEncoder</code> class.

     *

     * @param in the underlying stream.  <code>null</code> may be passed without

     *        error, though the resulting XMLDecoder will be useless

     * @param owner the owner of this stream.  <code>null</code> is a legal

     *        value

     * @param exceptionListener the exception handler for the stream, or

     *        <code>null</code> to use the default

     * @param cl the class loader used for instantiating objects.

     *        <code>null</code> indicates that the default class loader should

     *        be used

     * @since 1.5

     */

    public XMLDecoder(InputStream in, Object owner,

                      ExceptionListener exceptionListener, ClassLoader cl) {

        this(new InputSource(in), owner, exceptionListener, cl);

    }

    /**

     * Creates a new decoder to parse XML archives

     * created by the {@code XMLEncoder} class.

     * If the input source {@code is} is {@code null},

     * no exception is thrown and no parsing is performed.

     * This behavior is similar to behavior of other constructors

     * that use {@code InputStream} as a parameter.

     *

     * @param is  the input source to parse

     *

     * @since 1.7

     */

    public XMLDecoder(InputSource is) {

        this(is, null, null, null);

    }

    /**

     * Creates a new decoder to parse XML archives

     * created by the {@code XMLEncoder} class.

     *

     * @param is     the input source to parse

     * @param owner  the owner of this decoder

     * @param el     the exception handler for the parser,

     *               or {@code null} to use the default exception handler

     * @param cl     the class loader used for instantiating objects,

     *               or {@code null} to use the default class loader

     *

     * @since 1.7

     */

    private XMLDecoder(InputSource is, Object owner, ExceptionListener el, ClassLoader cl) {

        this.input = is;

        this.owner = owner;

        setExceptionListener(el);

        this.handler.setClassLoader(cl);

        this.handler.setOwner(this);

    }

    /**

     * This method closes the input stream associated

     * with this stream.

     */

    public void close() {

        if (parsingComplete()) {

            close(this.input.getCharacterStream());

            close(this.input.getByteStream());

        }

    }

    private void close(Closeable in) {

        if (in != null) {

            try {

                in.close();

            }

            catch (IOException e) {

                getExceptionListener().exceptionThrown(e);

            }

        }

    }

    private boolean parsingComplete() {

        if (this.input == null) {

            return false;

        }

        if (this.array == null) {

            this.handler.parse(this.input);

            this.array = this.handler.getObjects();

        }

        return true;

    }

    /**

     * Sets the exception handler for this stream to <code>exceptionListener</code>.

     * The exception handler is notified when this stream catches recoverable

     * exceptions.

     *

     * @param exceptionListener The exception handler for this stream;

     * if <code>null</code> the default exception listener will be used.

     *

     * @see #getExceptionListener

     */

    public void setExceptionListener(ExceptionListener exceptionListener) {

        if (exceptionListener == null) {

            exceptionListener = Statement.defaultExceptionListener;

        }

        this.handler.setExceptionListener(exceptionListener);

    }

    /**

     * Gets the exception handler for this stream.

     *

     * @return The exception handler for this stream.

     *     Will return the default exception listener if this has not explicitly been set.

     *

     * @see #setExceptionListener

     */

    public ExceptionListener getExceptionListener() {

        return this.handler.getExceptionListener();

    }

    /**

     * Reads the next object from the underlying input stream.

     *

     * @return the next object read

     *

     * @throws ArrayIndexOutOfBoundsException if the stream contains no objects

     *         (or no more objects)

     *

     * @see XMLEncoder#writeObject

     */

    public Object readObject() {

        return (parsingComplete())

                ? this.array[this.index++]

                : null;

    }

    /**

     * Sets the owner of this decoder to <code>owner</code>.

     *

     * @param owner The owner of this decoder.

     *

     * @see #getOwner

     */

    public void setOwner(Object owner) {

        this.owner = owner;

    }

    /**

     * Gets the owner of this decoder.

     *

     * @return The owner of this decoder.

     *

     * @see #setOwner

     */

    public Object getOwner() {

        return owner;

    }

    /**

     * Creates a new handler for SAX parser

     * that can be used to parse embedded XML archives

     * created by the {@code XMLEncoder} class.

     *

     * The {@code owner} should be used if parsed XML document contains

     * the method call within context of the <java> element.

     * The {@code null} value may cause illegal parsing in such case.

     * The same problem may occur, if the {@code owner} class

     * does not contain expected method to call. See details <a

     * href="http://java.sun.com/products/jfc/tsc/articles/persistence3/">here</a>.

     *

     * @param owner  the owner of the default handler

     *               that can be used as a value of <java> element

     * @param el     the exception handler for the parser,

     *               or {@code null} to use the default exception handler

     * @param cl     the class loader used for instantiating objects,

     *               or {@code null} to use the default class loader

     * @return an instance of {@code DefaultHandler} for SAX parser

     *

     * @since 1.7

     */

    public static DefaultHandler createHandler(Object owner, ExceptionListener el, ClassLoader cl) {

        DocumentHandler handler = new DocumentHandler();

        handler.setOwner(owner);

        handler.setExceptionListener(el);

        handler.setClassLoader(cl);

        return handler;

    }

}