com.helger.commons.idfactory

Class FileLongIDFactory

java.lang.Object

com.helger.commons.idfactory.AbstractPersistingLongIDFactory

com.helger.commons.idfactory.FileLongIDFactory

All Implemented Interfaces:

IBaseIDFactory, ILongIDFactory

@ThreadSafe
public class FileLongIDFactory
extends AbstractPersistingLongIDFactory

File based persisting ILongIDFactory implementation.

Author:

Philip Helger

Field Summary

Fields

Modifier and Type	Field and Description
static Charset	CHARSET_TO_USE The charset to use for writing the file
static int	DEFAULT_RESERVE_COUNT The default number of values to reserve with a single IO action

Constructor Summary

Constructors

Constructor and Description
FileLongIDFactory(File aFile)
FileLongIDFactory(File aFile, int nReserveCount)

Method Summary

Methods

Modifier and Type	Method and Description
boolean	equals(Object o)
int	hashCode()
protected long	readAndUpdateIDCounter(int nReserveCount) Read the current ID from the device.
String	toString()

Methods inherited from class com.helger.commons.idfactory.AbstractPersistingLongIDFactory

getNewID, getReserveCount

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

CHARSET_TO_USE

@Nonnull
public static final Charset CHARSET_TO_USE

The charset to use for writing the file

DEFAULT_RESERVE_COUNT

@Nonnegative
public static final int DEFAULT_RESERVE_COUNT

The default number of values to reserve with a single IO action

See Also:

Constant Field Values

Constructor Detail

FileLongIDFactory

public FileLongIDFactory(@Nonnull
                 File aFile)

FileLongIDFactory

public FileLongIDFactory(@Nonnull
                 File aFile,
                 @Nonnegative
                 int nReserveCount)

Method Detail

readAndUpdateIDCounter

protected final long readAndUpdateIDCounter(@Nonnegative
                          int nReserveCount)

Description copied from class: AbstractPersistingLongIDFactory

Read the current ID from the device. In case the method is called for a non-initialized device, 0 should be returned.
The update should write the read value plus the passed reserve count back to the device. This method should perform an atomic read and update to avoid that ID can be reused.
Pseudo code:

 protected long readAndUpdateIDCounter (int nReserveCount)
 {
   final long nRead = FileIO.read (file);
   FileIO.write (file, nRead + nReserveCount);
   return nRead;
 }
 

Specified by:

readAndUpdateIDCounter in class AbstractPersistingLongIDFactory

Parameters:

nReserveCount - the number that should be added to the read value. Always > 0.

Returns:

0 if this method is called for a non-initialized device, the value read from the device otherwise or CGlobal.ILLEGAL_ULONG in case of an error.

equals

public boolean equals(Object o)

Overrides:

equals in class AbstractPersistingLongIDFactory

hashCode

public int hashCode()

Overrides:

hashCode in class AbstractPersistingLongIDFactory

toString

public String toString()

Overrides:

toString in class AbstractPersistingLongIDFactory