| /* java.beans.XMLDecoder -- |
| Copyright (C) 2004, 2005, 2006 Free Software Foundation, Inc. |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath 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, or (at your option) |
| any later version. |
| |
| GNU Classpath 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 GNU Classpath; see the file COPYING. 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 java.beans; |
| |
| import gnu.java.beans.DefaultExceptionListener; |
| import gnu.java.beans.decoder.PersistenceParser; |
| |
| import java.io.IOException; |
| import java.io.InputStream; |
| import java.util.Iterator; |
| import java.util.NoSuchElementException; |
| |
| /** |
| * The XMLDecoder reads XML data that is structured according to |
| * <a href="http://java.sun.com/products/jfc/tsc/articles/persistence3/javabeans.dtd">this</a> DTD |
| * and creates objects according to the content. Usually such data is generated using the |
| * {@link XMLEncoder} class. |
| * <p> |
| * An example XML document might look like this: |
| * <code> |
| * <java> |
| * <string>Hello World</string> |
| * <int>200</int> |
| * </java> |
| * </code> |
| * <p>To read the <code>String</code> and the <code>Integer</code> instance the following can be used (assume |
| * the XML data can be obtained from the InputStream):</p> |
| * <code> |
| * XMLDecoder decoder = new XMLDecoder(inputStreamContainingXMLData); |
| * String message = (String) decoder.readObject(); |
| * Integer number = (Integer) decoder.readObject(); |
| * </code> |
| * <p>Besides this basic functionality the <code>XMLDecoder</code> has some more features that might come |
| * handy in certain situations:</p> |
| * <p>An owner object can be set using the <code>setOwner</code> method which can then be accessed when |
| * decoding. This feature is only useful if the XML data is aware of the owner object. Such data may |
| * look like this (assume that the owner object is a JFrame instance):</p> |
| * <code> |
| * <java> |
| * <void method="getOwner"> |
| * <void method="setVisible"> |
| * <boolean>true<boolean> |
| * </void> |
| * </void> |
| * </java> |
| * </code> |
| * This accesses the <code>JFrame</code> and makes it visible using the <code>setVisible</code> method. |
| * <p>Please note that changing the owner <b>after</b> the having read the first object has no effect, |
| * because all object have been decoded then.</p> |
| * <p>If the <code>XMLDecoder</code> is created with no {@link ExceptionListener} instance a default one |
| * is used that prints an error message to <code>System.err</code> whenever a recoverable exception |
| * is thrown. Recovarable exceptions occur when the XML data cannot be interpreted correctly (e.g |
| * unknown classes or methods, invocation on null, ...). In general be very careful when the |
| * <code>XMLDecoder</code> provoked such exceptions because the resulting object(s) may be in an |
| * undesirable state.</p> |
| * <p>Note that changing the ExceptionListener instance after <code>readObject</code> has been called |
| * once has no effect because the decoding is completed then.</p> |
| * <p>At last one can provide a specific <code>ClassLoader</code> which is then used when <code>Class</code> |
| * objects are accessed. See {@link java.lang.Class#forName(String, boolean, ClassLoader)} for details |
| * on this.</p> |
| * <p>Note: If the <code>InputStream</code> instance given to any of the constructors is <code>null</code> |
| * the resulting <code>XMLDecoder</code> will be silently (without any exception) useless. Each call |
| * to <code>readObject</code> will return <code>null</code> and never throws an |
| * <code>ArrayIndexOutOfBoundsException</code>.</p> |
| * |
| * @author Robert Schuster |
| * @since 1.4 |
| * @status updated to 1.5 |
| */ |
| public class XMLDecoder |
| { |
| private Object owner; |
| |
| private ExceptionListener exceptionListener; |
| |
| private InputStream inputStream; |
| |
| private boolean isStreamClosed; |
| |
| private ClassLoader classLoader; |
| |
| private Iterator iterator; |
| |
| /** Creates a XMLDecoder instance that parses the XML data of the given input stream. |
| * Using this constructor no special ClassLoader, a default ExceptionListener |
| * and no owner object is used. |
| * |
| * @param in InputStream to read XML data from. |
| */ |
| public XMLDecoder(InputStream in) |
| { |
| this(in, null); |
| } |
| |
| /** Creates a XMLDecoder instance that parses the XML data of the given input stream. |
| * Using this constructor no special ClassLoader and a default ExceptionListener |
| * is used. |
| * |
| * @param in InputStream to read XML data from. |
| * @param owner Owner object which can be accessed and modified while parsing. |
| */ |
| public XMLDecoder(InputStream in, Object owner) |
| { |
| this(in, owner, null); |
| } |
| |
| /** Creates a XMLDecoder instance that parses the XML data of the given input stream. |
| * If the ExceptionListener argument is null a default implementation is used. |
| * |
| * @param in InputStream to read XML data from. |
| * @param owner Owner object which can be accessed and modified while parsing. |
| * @param exceptionListener ExceptionListener instance to which exception notifications are send. |
| */ |
| public XMLDecoder( |
| InputStream in, |
| Object owner, |
| ExceptionListener exceptionListener) |
| { |
| this( |
| in, |
| owner, |
| exceptionListener, |
| Thread.currentThread().getContextClassLoader()); |
| } |
| |
| /** Creates a XMLDecoder instance that parses the XML data of the given input stream. |
| * If the ExceptionListener argument is null a default implementation is used. |
| * |
| * @param in InputStream to read XML data from. |
| * @param owner Owner object which can be accessed and modified while parsing. |
| * @param exceptionListener ExceptionListener instance to which exception notifications are send. |
| * @param cl ClassLoader instance that is used for calls to <code>Class.forName(String, boolean, ClassLoader)</code> |
| * @since 1.5 |
| */ |
| public XMLDecoder( |
| InputStream in, |
| Object owner, |
| ExceptionListener listener, |
| ClassLoader cl) |
| { |
| // initially here was a check for the validity of the InputStream argument but some |
| // great engineers decided that this API should silently discard this and behave rather |
| // odd: readObject will always return null ... |
| inputStream = in; |
| |
| setExceptionListener(listener); |
| |
| // validity of this object is checked in Class.forName() and therefore may be null |
| classLoader = cl; |
| |
| this.owner = owner; |
| } |
| |
| /** Closes the stream associated with this decoder. This should be done after having read all |
| * decoded objects. |
| * <p>See the description of the {@link #readObject()} for the effect caused by <code>close</code>.</p> |
| */ |
| public void close() |
| { |
| if (isStreamClosed) |
| { |
| return; |
| } |
| |
| try |
| { |
| inputStream.close(); |
| isStreamClosed = true; |
| } |
| catch (IOException e) |
| { |
| // bad style forced by original API design ... |
| } |
| } |
| |
| /** Returns the ExceptionListener instance associated with this decoder. |
| * <p>See the description of {@link XMLDecoder} class for more information on the ExceptionListener.</p> |
| * |
| * @return Current ExceptionListener of the decoder. |
| */ |
| public ExceptionListener getExceptionListener() |
| { |
| return exceptionListener; |
| } |
| |
| /** Returns the owner object of the decoder. This method is usually called |
| * from within the parsed XML data. |
| * <p>See the description of {@link XMLDecoder} class for more information on the owner object.</p> |
| * |
| * @return The owner object of this decoder. |
| */ |
| public Object getOwner() |
| { |
| return owner; |
| } |
| |
| /** Returns the next available decoded object. |
| * <p>Note that the actual decoding takes place when the method is called for the first time.</p> |
| * <p>If the <code>close</code> method was already called a <code>NoSuchElementException</code> |
| * is thrown.</p> |
| * <p>If the InputStream instance used in the constructors was <code>null</code> this method |
| * will always return <code>null</code> itself.</p> |
| * |
| * @return The next object in a sequence decoded from XML data. |
| * @throws ArrayIndexOutOfBoundsException When no more objects are available. |
| */ |
| public Object readObject() throws ArrayIndexOutOfBoundsException |
| { |
| // note: the RI does it this way ... |
| if(inputStream == null) { |
| return null; |
| } |
| |
| // note: the original API documentation says nothing on what to do |
| // when the stream was closed before readObject is called but it actually |
| // throws a NoSuchElementException - this behaviour is imitated here |
| if (isStreamClosed) |
| { |
| throw new NoSuchElementException("Cannot read any objects - XMLDecoder was already closed."); |
| } |
| |
| // creates the PersistenceParser (doing the parsing and decoding) and returns its |
| // Iterator on first invocation |
| if (iterator == null) |
| { |
| iterator = |
| new PersistenceParser( |
| inputStream, |
| exceptionListener, |
| classLoader, |
| this) |
| .iterator(); |
| } |
| |
| // note: done according to the official documentation |
| if (!iterator.hasNext()) |
| { |
| throw new ArrayIndexOutOfBoundsException("No more objects available from this XMLDecoder."); |
| } |
| |
| // returns just the next object if there was no problem |
| return iterator.next(); |
| } |
| |
| /** Sets the ExceptionListener instance to which notifications of exceptions are send |
| * while parsing the XML data. |
| * <p>See the description of {@link XMLDecoder} class for more information on the ExceptionListener.</p> |
| * |
| * @param listener |
| */ |
| public void setExceptionListener(ExceptionListener listener) |
| { |
| // uses a default implementation when null |
| if (listener == null) |
| { |
| listener = DefaultExceptionListener.INSTANCE; |
| } |
| exceptionListener = listener; |
| } |
| |
| /** Sets the owner object which can be accessed from the parsed XML data. |
| * <p>See the description of {@link XMLDecoder} class for more information on the owner object.</p> |
| * |
| * @param newOwner |
| */ |
| public void setOwner(Object newOwner) |
| { |
| owner = newOwner; |
| } |
| |
| } |