/*
* 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
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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 {@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;
}
}