org.apache.derby.iapi.services.io

Class FormatIdOutputStream

java.lang.Object

java.io.OutputStream

java.io.FilterOutputStream

java.io.DataOutputStream

org.apache.derby.iapi.services.io.FormatIdOutputStream

All Implemented Interfaces:

java.io.Closeable, java.io.DataOutput, java.io.Flushable, java.io.ObjectOutput, java.lang.AutoCloseable, ErrorInfo

public class FormatIdOutputStream
extends java.io.DataOutputStream
implements java.io.ObjectOutput, ErrorInfo

A stream for serializing objects with format id tags.

An ObjectOutput (henceforth 'out') preceeds objects it writes with a format id. The companion FormatIdInputStream (henceforth 'in') uses these format ids in parsing the stored data. The stream can be thought of as containing a sequence of (formatId,object) pairs interspersed with other data. The assumption is that out.writeObject() produces these pairs and in.readObject() uses the format ids to construct objects from the pairs that out.writeObject produced. The description below describes each supported pair and how in.readObject() processes it.

1. (NULL_FORMAT_ID, nothing) in.readObject() returns null.
2. (SRING_FORMAT_ID, UTF8 encoded string)in.readObject reads and returns this string.
3. (SERIALIZABLE_FORMAT_ID,serialized object) in.readObject() reads the object using java serialization and returns it.
4. (A format id for a Storable, isNull flag and object if isNull == false) (see note 1) in.readObject() reads the boolean isNull flag. If is null is true, in.readObject() returns a Storable object of the correct class which is null. If ifNull is false, in.readObject() restores the object using its readExternal() method.
5. (A format id for a Formatable which is not Storable, the stored object) (see note 1) in.readObject restores the object using its readExternal() method.

Note 1: The FormatIdInputStream uses Monitor.newInstanceFromIdentifier(format id) to get the class.

Note 2: An object may support more than one of the following interfaces Storable, Formatable, Serializable. In this case out.writeObject use the first of these interfaces which the object supports (based on the order listed here) to determine how to write the object.

Field Summary

Fields inherited from class java.io.DataOutputStream

written

Fields inherited from class java.io.FilterOutputStream

out

Constructor Summary

Constructors

Constructor and Description
FormatIdOutputStream(java.io.OutputStream out) Constructor for a FormatIdOutputStream

Method Summary

Methods

Modifier and Type	Method and Description
java.lang.String	getErrorInfo()
java.lang.Exception	getNestedException()
void	setOutput(java.io.OutputStream out) Set the OutputStream for this FormatIdOutputStream to the stream provided.
void	writeObject(java.lang.Object ref) Write a format id for the object provied followed by the object itself to this FormatIdOutputStream.

Methods inherited from class java.io.DataOutputStream

flush, size, write, write, writeBoolean, writeByte, writeBytes, writeChar, writeChars, writeDouble, writeFloat, writeInt, writeLong, writeShort, writeUTF

Methods inherited from class java.io.FilterOutputStream

close, write

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.io.ObjectOutput

close, flush, write, write, write

Methods inherited from interface java.io.DataOutput

writeBoolean, writeByte, writeBytes, writeChar, writeChars, writeDouble, writeFloat, writeInt, writeLong, writeShort, writeUTF

Constructor Detail

FormatIdOutputStream

public FormatIdOutputStream(java.io.OutputStream out)

Constructor for a FormatIdOutputStream

Parameters:

out - output goes here.

Method Detail

writeObject

public void writeObject(java.lang.Object ref)
                 throws java.io.IOException

Write a format id for the object provied followed by the object itself to this FormatIdOutputStream.

Specified by:

writeObject in interface java.io.ObjectOutput

Parameters:

ref - a reference to the object.

Throws:

java.io.IOException - the exception.

setOutput

public void setOutput(java.io.OutputStream out)

Set the OutputStream for this FormatIdOutputStream to the stream provided. It is the responsibility of the caller to flush or close (as required) the previous stream this class was attached to.

Parameters:

out - The new output stream.

getErrorInfo

public java.lang.String getErrorInfo()

Specified by:

getErrorInfo in interface ErrorInfo

getNestedException

public java.lang.Exception getNestedException()

Specified by:

getNestedException in interface ErrorInfo