net.java.sip.communicator.impl.fileaccess
Class FailSafeTransactionImpl

java.lang.Object
  net.java.sip.communicator.impl.fileaccess.FailSafeTransactionImpl

All Implemented Interfaces:

FailSafeTransaction

public class FailSafeTransactionImpl
extends Object
implements FailSafeTransaction

A failsafe transaction class. By failsafe we mean here that the file concerned always stays in a coherent state. This class use the transactional model.

Author:

Benoit Pradelle

Constructor Summary

protected

FailSafeTransactionImpl(File file) Creates a new transaction.

Method Summary

void	beginTransaction() Begins a new transaction.
void	commit() Closes the transaction and commit the changes.
void	restoreFile() Ensure that the file accessed is in a coherent state.
void	rollback() Closes the transation and cancel the changes.

Methods inherited from class java.lang.Object

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

Constructor Detail

FailSafeTransactionImpl

protected FailSafeTransactionImpl(File file)
                           throws NullPointerException

Creates a new transaction.

Parameters:

file - The file associated with this transaction

Throws:

NullPointerException - if the file is null

Method Detail

restoreFile

public void restoreFile()
                 throws IllegalStateException,
                        IOException

Ensure that the file accessed is in a coherent state. This function is useful to do a failsafe read without starting a transaction.

Specified by:

restoreFile in interface FailSafeTransaction

Throws:

IllegalStateException - if the file doesn't exists anymore

IOException - if an IOException occurs during the file restoration

beginTransaction

public void beginTransaction()
                      throws IllegalStateException,
                             IOException

Begins a new transaction. If a transaction is already active, commits the changes and begin a new transaction. A transaction can be closed by a commit or rollback operation. When the transaction begins, the file is restored to a coherent state if needed.

Specified by:

beginTransaction in interface FailSafeTransaction

Throws:

IllegalStateException - if the file doesn't exists anymore

IOException - if an IOException occurs during the transaction creation

commit

public void commit()
            throws IllegalStateException,
                   IOException

Closes the transaction and commit the changes. Everything written in the file during the transaction is saved.

Specified by:

commit in interface FailSafeTransaction

Throws:

IllegalStateException - if the file doesn't exists anymore

IOException - if an IOException occurs during the operation

rollback

public void rollback()
              throws IllegalStateException,
                     IOException

Closes the transation and cancel the changes. Everything written in the file during the transaction is NOT saved.

Specified by:

rollback in interface FailSafeTransaction

Throws:

IllegalStateException - if the file doesn't exists anymore

IOException - if an IOException occurs during the operation