edu.umd.cs.piccolo.util
Class PObjectOutputStream

java.lang.Object
  java.io.OutputStream
      java.io.ObjectOutputStream
          edu.umd.cs.piccolo.util.PObjectOutputStream

All Implemented Interfaces:

java.io.Closeable, java.io.DataOutput, java.io.Flushable, java.io.ObjectOutput, java.io.ObjectStreamConstants

public class PObjectOutputStream
extends java.io.ObjectOutputStream

PObjectOutputStream is an extension of ObjectOutputStream to handle optional elements. This is similar to the concept of Java's "weak references", but applied to object serialization rather than garbage collection. Here, PObjectOutputStream provides a method, writeConditionalObject, which only serializes the specified object to the stream if there is a strong reference (if it has been written somewhere else using writeObject()) to that object elsewhere in the stream.

To discover strong references to objects, PObjectOutputStream uses a two-phase writing process. First, a "discovery" phase is used to find out what objects are about to be serialized. This works by effectively serializing the object graph to /dev/null, recording which objects are unconditionally written using the standard writeObject method. Then, in the second "write" phase, ObjectOutputStream actually serializes the data to the output stream. During this phase, calls to writeConditionalObject() will only write the specified object if the object was found to be serialized during the discovery stage. If the object was not recorded during the discovery stage, a an optional null (the default) is unconditionally written in place of the object. To skip writting out the null use writeConditionalObject(object, false)

By careful implementation of readObject and writeObject methods, streams serialized using PObjectOutputStream can be deserialized using the standard ObjectInputStream.

Version:

1.0

Author:

Jon Meyer, Jesse Grosjean

Nested Class Summary

Nested classes/interfaces inherited from class java.io.ObjectOutputStream

java.io.ObjectOutputStream.PutField

Field Summary

Fields inherited from interface java.io.ObjectStreamConstants

baseWireHandle, PROTOCOL_VERSION_1, PROTOCOL_VERSION_2, SC_BLOCK_DATA, SC_ENUM, SC_EXTERNALIZABLE, SC_SERIALIZABLE, SC_WRITE_METHOD, STREAM_MAGIC, STREAM_VERSION, SUBCLASS_IMPLEMENTATION_PERMISSION, SUBSTITUTION_PERMISSION, TC_ARRAY, TC_BASE, TC_BLOCKDATA, TC_BLOCKDATALONG, TC_CLASS, TC_CLASSDESC, TC_ENDBLOCKDATA, TC_ENUM, TC_EXCEPTION, TC_LONGSTRING, TC_MAX, TC_NULL, TC_OBJECT, TC_PROXYCLASSDESC, TC_REFERENCE, TC_RESET, TC_STRING

Constructor Summary

PObjectOutputStream(java.io.OutputStream out)

Method Summary

protected void	recordUnconditionallyWritten(java.lang.Object aRoot)
void	reset()
static byte[]	toByteArray(java.lang.Object aRoot)
void	writeConditionalObject(java.lang.Object object)
void	writeObjectTree(java.lang.Object aRoot)

Methods inherited from class java.io.ObjectOutputStream

annotateClass, annotateProxyClass, close, defaultWriteObject, drain, enableReplaceObject, flush, putFields, replaceObject, useProtocolVersion, write, write, write, writeBoolean, writeByte, writeBytes, writeChar, writeChars, writeClassDescriptor, writeDouble, writeFields, writeFloat, writeInt, writeLong, writeObject, writeObjectOverride, writeShort, writeStreamHeader, writeUnshared, writeUTF

Methods inherited from class java.lang.Object

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

Constructor Detail

PObjectOutputStream

public PObjectOutputStream(java.io.OutputStream out)
                    throws java.io.IOException

Throws:

java.io.IOException

Method Detail

toByteArray

public static byte[] toByteArray(java.lang.Object aRoot)
                          throws java.io.IOException

Throws:

java.io.IOException

writeObjectTree

public void writeObjectTree(java.lang.Object aRoot)
                     throws java.io.IOException

Throws:

java.io.IOException

writeConditionalObject

public void writeConditionalObject(java.lang.Object object)
                            throws java.io.IOException

Throws:

java.io.IOException

reset

public void reset()
           throws java.io.IOException

Overrides:

reset in class java.io.ObjectOutputStream

Throws:

java.io.IOException

recordUnconditionallyWritten

protected void recordUnconditionallyWritten(java.lang.Object aRoot)
                                     throws java.io.IOException

Throws:

java.io.IOException