Serializing a Stream

<br />public class DocumentDescription implements Serializable,<br /> PrinterConstants {<br /> private transient InputStream _actualDocument;<br /> private int _length;<br /> private int _documentType;<br /> private boolean _printTwoSided;<br /> private int _printQuality;<br /> public DocumentDescription( ) {<br /> // zero arg constructor needed for serialization<br /> }<br />....<br />private void writeObject(java.io.ObjectOutputStream out) throws<br />IOException {<br /> out.defaultWriteObject( );<br /> copy(_actualDocument, out);<br />}<br />private void readObject(java.io.ObjectInputStream in) throws<br />IOException,<br />ClassNotFoundException {<br /> in.defaultReadObject( );<br /> ByteArrayOutputStream temporaryBuffer = new ByteArrayOutputStream( );<br /> copy(in, temporaryBuffer, _length);<br /> _actualDocument = new DataInputStream(new ByteArrayInputStream(temporaryBuffer.toByteArray( )));<br /> }<br />}<br />
We start by declaring _actualDocument to be transient. transient is a Java keyword that
tells the serialization mechanism not to serialize the variable's value out. We then implement
writeObject( ), which does two things:

· Calls out.defaultWriteObject( ). This invokes the generic serialization
mechanism (which is the default) to write out all nontransient objects. That is, when
out.defaultWriteObject( ) is called, everything but _actualDocument has been
encoded in the stream.

· Copies _actualDocument to the stream, exactly as we did for the socket-based version
of the program.
Similarly, in readObject( ), we first call defaultReadObject( ), which retrieves all the
nontransient values, including _length, from the stream. We then read _actualDocument
from the stream.