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java.beans
Class XMLDecoder  

java.lang.Object
  java.beans.XMLDecoder

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public class XMLDecoder

extends java.lang.Object

The XMLDecoder reads XML data that is structured according to this DTD and creates objects according to the content. Usually such data is generated using the XMLEncoder class.

An example XML document might look like this: <java> <string>Hello World</string> <int>200</int> </java>

To read the String and the Integer instance the following can be used (assume the XML data can be obtained from the InputStream):

XMLDecoder decoder = new XMLDecoder(inputStreamContainingXMLData); String message = (String) decoder.readObject(); Integer number = (Integer) decoder.readObject();

Besides this basic functionality the XMLDecoder has some more features that might come handy in certain situations:

An owner object can be set using the setOwner 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):

<java> <void method="getOwner"> <void method="setVisible"> <boolean>true<boolean> </void> </void> </java> This accesses the JFrame and makes it visible using the setVisible method.

Please note that changing the owner after the having read the first object has no effect, because all object have been decoded then.

If the XMLDecoder is created with no ExceptionListener instance a default one is used that prints an error message to System.err 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 XMLDecoder provoked such exceptions because the resulting object(s) may be in an undesirable state.

Note that changing the ExceptionListener instance after readObject has been called once has no effect because the decoding is completed then.

At last one can provide a specific ClassLoader which is then used when Class objects are accessed. See Class.forName(String, boolean, ClassLoader)>Class.forName(String, boolean, ClassLoader) 55 for details on this.

Note: If the InputStream instance given to any of the constructors is null the resulting XMLDecoder will be silently (without any exception) useless. Each call to readObject will return null and never throws an ArrayIndexOutOfBoundsException.

Since:

1.4

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Field Summary
private  java.lang.ClassLoader	classLoader
private  ExceptionListener	exceptionListener
private  java.io.InputStream	inputStream
private  boolean	isStreamClosed
private  java.util.Iterator	iterator
private  java.lang.Object	owner

 

Constructor Summary

XMLDecoder(java.io.InputStream in)           Creates a XMLDecoder instance that parses the XML data of the given input stream.

XMLDecoder(java.io.InputStream in, java.lang.Object owner)           Creates a XMLDecoder instance that parses the XML data of the given input stream.

XMLDecoder(java.io.InputStream in, java.lang.Object owner, ExceptionListener exceptionListener)           Creates a XMLDecoder instance that parses the XML data of the given input stream.

XMLDecoder(java.io.InputStream in, java.lang.Object owner, ExceptionListener listener, java.lang.ClassLoader cl)           Creates a XMLDecoder instance that parses the XML data of the given input stream.

 

Method Summary
void	close()           Closes the stream associated with this decoder.
ExceptionListener	getExceptionListener()           Returns the ExceptionListener instance associated with this decoder.
java.lang.Object	getOwner()           Returns the owner object of the decoder.
java.lang.Object	readObject()           Returns the next available decoded object.
void	setExceptionListener(ExceptionListener listener)           Sets the ExceptionListener instance to which notifications of exceptions are send while parsing the XML data.
void	setOwner(java.lang.Object newOwner)           Sets the owner object which can be accessed from the parsed XML data.

 

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

 

Field Detail

owner

private java.lang.Object owner

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exceptionListener

private ExceptionListener exceptionListener

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inputStream

private java.io.InputStream inputStream

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isStreamClosed

private boolean isStreamClosed

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classLoader

private java.lang.ClassLoader classLoader

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iterator

private java.util.Iterator iterator

Constructor Detail

XMLDecoder

public XMLDecoder(java.io.InputStream in)

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.

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XMLDecoder

public XMLDecoder(java.io.InputStream in,
                  java.lang.Object owner)

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.

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XMLDecoder

public XMLDecoder(java.io.InputStream in,
                  java.lang.Object owner,
                  ExceptionListener exceptionListener)

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.

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XMLDecoder

public XMLDecoder(java.io.InputStream in,
                  java.lang.Object owner,
                  ExceptionListener listener,
                  java.lang.ClassLoader cl)

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.

Since:

1.5

Method Detail

close

public void close()

Closes the stream associated with this decoder. This should be done after having read all decoded objects.

See the description of the readObject() 55 for the effect caused by close.

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getExceptionListener

public ExceptionListener getExceptionListener()

Returns the ExceptionListener instance associated with this decoder.

See the description of XMLDecoder class for more information on the ExceptionListener.

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getOwner

public java.lang.Object getOwner()

Returns the owner object of the decoder. This method is usually called from within the parsed XML data.

See the description of XMLDecoder class for more information on the owner object.

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readObject

public java.lang.Object readObject()
                            throws java.lang.ArrayIndexOutOfBoundsException

Returns the next available decoded object.

Note that the actual decoding takes place when the method is called for the first time.

If the close method was already called a NoSuchElementException is thrown.

If the InputStream instance used in the constructors was null this method will always return null itself.

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setExceptionListener

public void setExceptionListener(ExceptionListener listener)

Sets the ExceptionListener instance to which notifications of exceptions are send while parsing the XML data.

See the description of XMLDecoder class for more information on the ExceptionListener.

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setOwner

public void setOwner(java.lang.Object newOwner)

Sets the owner object which can be accessed from the parsed XML data.

See the description of XMLDecoder class for more information on the owner object.

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Overview  Package   Class  Use  Deprecated  Index
Home >> All >> java >> [ beans overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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