AutoCloseable
public class XMLEncoder extends Encoder implements AutoCloseable
XMLEncoder
class is a complementary alternative to the ObjectOutputStream
and can used to generate a textual representation of a JavaBean in the same way that the ObjectOutputStream
can be used to create binary representation of Serializable
objects. For example, the following fragment can be used to create a textual representation the supplied JavaBean and all its properties: XMLEncoder e = new XMLEncoder( new BufferedOutputStream( new FileOutputStream("Test.xml"))); e.writeObject(new JButton("Hello, world")); e.close();Despite the similarity of their APIs, the
XMLEncoder
class is exclusively designed for the purpose of archiving graphs of JavaBeans as textual representations of their public properties. Like Java source files, documents written this way have a natural immunity to changes in the implementations of the classes involved. The ObjectOutputStream
continues to be recommended for interprocess communication and general purpose serialization. The XMLEncoder
class provides a default denotation for JavaBeans in which they are represented as XML documents complying with version 1.0 of the XML specification and the UTF-8 character encoding of the Unicode/ISO 10646 character set. The XML documents produced by the XMLEncoder
class are:
XMLEncoder
class uses a redundancy elimination algorithm internally so that the default values of a Bean's properties are not written to the stream. Below is an example of an XML archive containing some user interface components from the swing toolkit:
<?xml version="1.0" encoding="UTF-8"?> <java version="1.0" class="java.beans.XMLDecoder"> <object class="javax.swing.JFrame"> <void property="name"> <string>frame1</string> </void> <void property="bounds"> <object class="java.awt.Rectangle"> <int>0</int> <int>0</int> <int>200</int> <int>200</int> </object> </void> <void property="contentPane"> <void method="add"> <object class="javax.swing.JButton"> <void property="label"> <string>Hello</string> </void> </object> </void> </void> <void property="visible"> <boolean>true</boolean> </void> </object> </java>The XML syntax uses the following conventions:
Although all object graphs may be written using just these three tags, the following definitions are included so that common data structures can be expressed more concisely:
Integer
class could be written: <int>123</int>. Note that the XMLEncoder
class uses Java's reflection package in which the conversion between Java's primitive types and their associated "wrapper classes" is handled internally. The API for the XMLEncoder
class itself deals only with Object
s. For more information you might also want to check out Using XMLEncoder, an article in The Swing Connection.
Constructor | Description |
---|---|
XMLEncoder |
Creates a new XML encoder to write out JavaBeans to the stream out using an XML encoding. |
XMLEncoder |
Creates a new XML encoder to write out JavaBeans to the stream out using the given charset starting from the given indentation . |
Modifier and Type | Method | Description |
---|---|---|
void |
close() |
This method calls flush , writes the closing postamble and then closes the output stream associated with this stream. |
void |
flush() |
This method writes out the preamble associated with the XML encoding if it has not been written already and then writes out all of the values that been written to the stream since the last time flush was called. |
Object |
getOwner() |
Gets the owner of this encoder. |
void |
setOwner |
Sets the owner of this encoder to owner . |
void |
writeExpression |
Records the Expression so that the Encoder will produce the actual output when the stream is flushed. |
void |
writeObject |
Write an XML representation of the specified object to the output. |
void |
writeStatement |
Records the Statement so that the Encoder will produce the actual output when the stream is flushed. |
get, getExceptionListener, getPersistenceDelegate, remove, setExceptionListener, setPersistenceDelegate
public XMLEncoder(OutputStream out)
out
using an XML encoding.out
- the stream to which the XML representation of the objects will be writtenIllegalArgumentException
- if out
is null
public XMLEncoder(OutputStream out, String charset, boolean declaration, int indentation)
out
using the given charset
starting from the given indentation
.out
- the stream to which the XML representation of the objects will be writtencharset
- the name of the requested charset; may be either a canonical name or an aliasdeclaration
- whether the XML declaration should be generated; set this to false
when embedding the contents in another XML documentindentation
- the number of space characters to indent the entire XML document byIllegalArgumentException
- if out
or charset
is null
, or if indentation
is less than 0IllegalCharsetNameException
- if charset
name is illegalUnsupportedCharsetException
- if no support for the named charset is available in this instance of the Java virtual machineUnsupportedOperationException
- if loaded charset does not support encodingpublic void setOwner(Object owner)
owner
.owner
- The owner of this encoder.public Object getOwner()
public void writeObject(Object o)
writeObject
in class Encoder
o
- The object to be written to the stream.public void writeStatement(Statement oldStm)
This method should only be invoked within the context of initializing a persistence delegate.
writeStatement
in class Encoder
oldStm
- The statement that will be written to the stream.public void writeExpression(Expression oldExp)
This method should only be invoked within the context of initializing a persistence delegate or setting up an encoder to read from a resource bundle.
For more information about using resource bundles with the XMLEncoder, see Creating Internationalized Applications,
writeExpression
in class Encoder
oldExp
- The expression that will be written to the stream.public void flush()
flush
was called. After flushing, all internal references to the values that were written to this stream are cleared.public void close()
flush
, writes the closing postamble and then closes the output stream associated with this stream.close
in interface AutoCloseable
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https://docs.oracle.com/en/java/javase/21/docs/api/java.desktop/java/beans/XMLEncoder.html