Java tutorial
/* * Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved. * 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 * or visit www.oracle.com if you need additional information or have any * questions. */ 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 {@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 {@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 {@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 {@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 {@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 {@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) { 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 {@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. * * @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}. * * @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://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 <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; } }