org.apache.commons.transaction.file
Class FileSequence

java.lang.Object
  org.apache.commons.transaction.file.FileSequence

public class FileSequence
extends Object

Fail-Safe sequence store implementation using the file system. Works by versioning values of sequences and throwing away all versions, but the current and the previous one.

Field Summary

protected String

storeDir

Constructor Summary

FileSequence(String storeDir)
Creates a new resource manager operation on the specified directories.

Method Summary

boolean	create(String sequenceName, long initialValue) Creates a sequence if it does not already exist.
boolean	delete(String sequenceName) Deletes a sequence if it exists.
boolean	exists(String sequenceName) Checks if the sequence already exists.
protected String	getPathI(String sequenceName)
protected String	getPathII(String sequenceName)
long	nextSequenceValueBottom(String sequenceName, long increment) Gets the next value of the sequence.
protected long	read(String sequenceName)
protected long	readFromPath(String path)
protected void	write(String sequenceName, long value)
protected void	writeToPath(String path, long value)

Methods inherited from class java.lang.Object

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

Field Detail

storeDir

protected final String storeDir

Constructor Detail

FileSequence

public FileSequence(String storeDir)

Creates a new resource manager operation on the specified directories.

Parameters:

storeDir - directory where sequence information is stored

Method Detail

exists

public boolean exists(String sequenceName)

Checks if the sequence already exists.

Parameters:

sequenceName - the name of the sequence you want to check

Returns:

true if the sequence already exists, false otherwise

create

public boolean create(String sequenceName,
                      long initialValue)

Creates a sequence if it does not already exist.

Parameters:

sequenceName - the name of the sequence you want to create

Returns:

true if the sequence has been created, false if it already existed

delete

public boolean delete(String sequenceName)

Deletes a sequence if it exists.

Parameters:

sequenceName - the name of the sequence you want to delete

Returns:

true if the sequence has been deleted, false if not

nextSequenceValueBottom

public long nextSequenceValueBottom(String sequenceName,
                                    long increment)

Gets the next value of the sequence.

Parameters:

sequenceName - the name of the sequence you want the next value for

increment - the increment for the sequence, i.e. how much to add to the sequence with this call

Returns:

the next value of the sequence not yet incremented, i.e. the increment is recorded internally, but not returned with the next call to this method

Throws:

ResourceManagerException - if anything goes wrong while accessing the sequence

read

protected long read(String sequenceName)

write

protected void write(String sequenceName,
                     long value)

getPathI

protected String getPathI(String sequenceName)

getPathII

protected String getPathII(String sequenceName)

readFromPath

protected long readFromPath(String path)
                     throws NumberFormatException,
                            FileNotFoundException,
                            IOException

Throws:

NumberFormatException

FileNotFoundException

IOException

writeToPath

protected void writeToPath(String path,
                           long value)