org.apache.river.reliableLog

Class LogHandler

java.lang.Object

org.apache.river.reliableLog.LogHandler

public abstract class LogHandler
extends Object

A LogHandler represents snapshots and update records as serializable objects.

This implementation does not know how to create an initial snaphot or apply an update to a snapshot. The client must specify these methods via a subclass.

Author:

Sun Microsystems, Inc.

See Also:

ReliableLog

Constructor Summary

Constructors

Constructor and Description
LogHandler() Creates a LogHandler for a ReliableLog.

Method Summary

Modifier and Type	Method and Description
abstract void	applyUpdate(Object update) Reads a stably logged update (a serializable object) from a stream.
void	readUpdate(InputStream in) Reads a stably logged update (a serializable object) from a stream.
abstract void	recover(InputStream in) Read the snapshot from a stream.
abstract void	snapshot(OutputStream out) Writes the snapshot to a stream.
void	writeUpdate(OutputStream out, Object value) Writes the representation (a serializable object) of an update to a stream.

Methods inherited from class java.lang.Object

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

Constructor Detail

LogHandler

public LogHandler()

Creates a LogHandler for a ReliableLog.

Method Detail

snapshot

public abstract void snapshot(OutputStream out)
                       throws Exception

Writes the snapshot to a stream. This callback is invoked when the client calls the snaphot method of ReliableLog.

Parameters:

out - the output stream

Throws:

Exception - can raise any exception

recover

public abstract void recover(InputStream in)
                      throws Exception

Read the snapshot from a stream. This callback is invoked when the client calls the recover method of ReliableLog.

Parameters:

in - the input stream

Throws:

Exception - can raise any exception

writeUpdate

public void writeUpdate(OutputStream out,
                        Object value)
                 throws Exception

Writes the representation (a serializable object) of an update to a stream. This callback is invoked when the client calls the update method of ReliableLog.

Parameters:

out - the output stream

value - the update object

Throws:

Exception - can raise any exception

readUpdate

public void readUpdate(InputStream in)
                throws Exception

Reads a stably logged update (a serializable object) from a stream. This callback is invoked during recovery, once for every record in the log. After reading the update, this method invokes the applyUpdate (abstract) method in order to execute the update.

Parameters:

in - the input stream

Throws:

Exception - can raise any exception

applyUpdate

public abstract void applyUpdate(Object update)
                          throws Exception

Reads a stably logged update (a serializable object) from a stream. This callback is invoked during recovery, once for every record in the log. After reading the update, this method is invoked in order to execute the update.

Parameters:

update - the update object

Throws:

Exception - can raise any exception