https://openjdk.java.net/ 
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 * Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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).
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 * 2 along with this work; if not, write to the Free Software Foundation,
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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 java.security.AccessControlContext;
import java.security.AccessController;
import java.security.PrivilegedAction;

import org.xml.sax.InputSource;
import org.xml.sax.helpers.DefaultHandler;


The XMLDecoder class is used to read XML documents created using the XMLEncoder and is used just like the ObjectInputStream. For example, one can use the following fragment to read the first object defined in an XML document written by the XMLEncoder class: 
      XMLDecoder d = new XMLDecoder(
                         new BufferedInputStream(
                             new FileInputStream("Test.xml")));
      Object result = d.readObject();
      d.close();




For more information you might also want to check out

Long Term Persistence of JavaBeans Components: XML Schema,
an article in The Swing Connection.

Author:Philip Milne
See Also:
Since:1.4
/**
 * The {@code XMLDecoder} class is used to read XML documents
 * created using the {@code XMLEncoder} and is used just like
 * the {@code ObjectInputStream}. For example, one can use
 * the following fragment to read the first object defined
 * in an XML document written by the {@code XMLEncoder}
 * 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://www.oracle.com/technetwork/java/persistence3-139471.html">
 * 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 AccessControlContext acc = AccessController.getContext();
    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 XMLEncoder class. 
Params:
  • in – The underlying stream.
See Also:
/**
     * Creates a new input stream for reading archives
     * created by the {@code XMLEncoder} 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 XMLEncoder class. 
Params:
  • in – The underlying stream.
  • owner – The owner of this stream.
/**
     * Creates a new input stream for reading archives
     * created by the {@code XMLEncoder} 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 XMLEncoder class. 
Params:
  • in – the underlying stream.
  • owner – the owner of this stream.
  • exceptionListener – the exception handler for the stream; if null the default exception listener will be used.
/**
     * Creates a new input stream for reading archives
     * created by the {@code XMLEncoder} class.
     *
     * @param in the underlying stream.
     * @param owner the owner of this stream.
     * @param exceptionListener the exception handler for the stream;
     *        if {@code null} 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 XMLEncoder class. 
Params:
  • in – the underlying stream. null may be passed without error, though the resulting XMLDecoder will be useless
  • owner – the owner of this stream. null is a legal value
  • exceptionListener – the exception handler for the stream, or null to use the default
  • cl – the class loader used for instantiating objects. null indicates that the default class loader should be used
Since:1.5
/**
     * Creates a new input stream for reading archives
     * created by the {@code XMLEncoder} class.
     *
     * @param in the underlying stream.  {@code null} may be passed without
     *        error, though the resulting XMLDecoder will be useless
     * @param owner the owner of this stream.  {@code null} is a legal
     *        value
     * @param exceptionListener the exception handler for the stream, or
     *        {@code null} to use the default
     * @param cl the class loader used for instantiating objects.
     *        {@code null} 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 XMLEncoder class. If the input source is is null, no exception is thrown and no parsing is performed. This behavior is similar to behavior of other constructors that use InputStream as a parameter. 
Params:
  • is –  the input source to parse
Since:1.7
/**
     * 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 XMLEncoder class. 
Params:
  • is –     the input source to parse
  • owner –  the owner of this decoder
  • el –  the exception handler for the parser, or null to use the default exception handler
  • cl –  the class loader used for instantiating objects, or null to use the default class loader
Since:1.7
/**
     * 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.

/**
     * 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) {
            if ((this.acc == null) && (null != System.getSecurityManager())) {
                throw new SecurityException("AccessControlContext is not set");
            }
            AccessController.doPrivileged(new PrivilegedAction<Void>() {
                public Void run() {
                    XMLDecoder.this.handler.parse(XMLDecoder.this.input);
                    return null;
                }
            }, this.acc);
            this.array = this.handler.getObjects();
        }
        return true;
    }

    
Sets the exception handler for this stream to exceptionListener. The exception handler is notified when this stream catches recoverable exceptions. 
Params:
  • exceptionListener – The exception handler for this stream; if null the default exception listener will be used.
See Also:
/**
     * Sets the exception handler for this stream to {@code exceptionListener}.
     * The exception handler is notified when this stream catches recoverable
     * exceptions.
     *
     * @param exceptionListener The exception handler for this stream;
     * if {@code null} 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.

See Also:
Returns:The exception handler for this stream.
    Will return the default exception listener if this has not explicitly been set.
/**
     * 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.

Throws:
See Also:
Returns:the next object read
/**
     * 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 owner. 
Params:
  • owner – The owner of this decoder.
See Also:
/**
     * Sets the owner of this decoder to {@code owner}.
     *
     * @param owner The owner of this decoder.
     *
     * @see #getOwner
     */
    public void setOwner(Object owner) {
        this.owner = owner;
    }

    
Gets the owner of this decoder.

See Also:
Returns:The owner of this decoder.
/**
     * 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 XMLEncoder class. The owner should be used if parsed XML document contains the method call within context of the <java> element. The null value may cause illegal parsing in such case. The same problem may occur, if the owner class does not contain expected method to call. See details 
here.

Params:
  • owner –  the owner of the default handler
              that can be used as a value of <java> element
  • el –  the exception handler for the parser, or null to use the default exception handler
  • cl –  the class loader used for instantiating objects, or null to use the default class loader
Returns:an instance of DefaultHandler for SAX parser
Since:1.7
/**
     * 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 &lt;java&gt; 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://www.oracle.com/technetwork/java/persistence3-139471.html">
     * here</a>.
     *
     * @param owner  the owner of the default handler
     *               that can be used as a value of &lt;java&gt; 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;
    }
}