net.sf.ehcache.store
Class DiskStore

java.lang.Object
  net.sf.ehcache.store.DiskStore

All Implemented Interfaces:

Store

public class DiskStore

extends java.lang.Object

implements Store

A disk cache implementation.

Version:

$Id: DiskStore.java,v 1.25 2004/12/02 07:35:38 gregluck Exp $

Author:

Adam Murdoch, Greg Luck

Field Summary

Fields inherited from interface net.sf.ehcache.store.Store

CACHE_HUB, DISK_CACHE, STATUS_ALIVE, STATUS_DISPOSED, STATUS_ERROR, STATUS_UNINITIALISED

Constructor Summary

DiskStore(Cache cache, java.lang.String diskPath)
Creates a disk store.

Method Summary

float	calculateDataFileSparseness() The design of the layout on the data file means that there will be small gaps created when DiskElements are reused.
void	dispose() Shuts down the disk store in preparation for cache shutdown If a VM crash happens, the shutdown hook will not run.
Element	get(java.io.Serializable key) Gets an Element from the Disk Store.
int	getCacheType() Returns the store type.
java.lang.String	getDataFileName()
java.lang.String	getDataFilePath()
long	getDataFileSize()
java.lang.String	getIndexFileName()
long	getIndexFileSize()
java.lang.Object[]	getKeyArray() Gets an Array of the keys for all elements in the disk store.
java.lang.String	getName() Returns the cache name this disk cache is spooling for
Element	getQuiet(java.io.Serializable key) Gets an Element from the Disk Store, without updating statistics
int	getSize() Returns the current store size.
int	getStatus() Returns the cache status.
long	getTotalFileSize()
long	getUsedDataSize() When elements are deleted, spaces are left in the file.
boolean	isExpiryThreadAlive() The expiry thread is started provided the cache is not eternal If started it will continue to run until the dispose() method is called, at which time it should be interrupted and then die.
boolean	isSpoolEmpty() Whether there are any elements waiting to be spooled to disk.
void	put(Element entry) Puts an item into the cache.
boolean	remove(java.io.Serializable key) Removes an item from the cache.
void	removeAll() Removes all cached items from the cache.
java.lang.String	toString() Returns a String representation of the DiskStore

Methods inherited from class java.lang.Object

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

Constructor Detail

DiskStore

public DiskStore(Cache cache,
                 java.lang.String diskPath)

Creates a disk store.

Parameters:

cache - the Cache that the store is part of

diskPath - the directory in which to create data and index files

Method Detail

getCacheType

public int getCacheType()

Returns the store type.

Specified by:

getCacheType in interface Store

Returns:

The cacheType value

getName

public java.lang.String getName()

Returns the cache name this disk cache is spooling for

Specified by:

getName in interface Store

getStatus

public int getStatus()

Returns the cache status.

Specified by:

getStatus in interface Store

get

public Element get(java.io.Serializable key)
            throws java.io.IOException

Gets an Element from the Disk Store.

Specified by:

get in interface Store

Returns:

The element

Throws:

java.io.IOException

getQuiet

public Element getQuiet(java.io.Serializable key)
                 throws java.io.IOException

Gets an Element from the Disk Store, without updating statistics

Returns:

The element

Throws:

java.io.IOException

getKeyArray

public java.lang.Object[] getKeyArray()

Gets an Array of the keys for all elements in the disk store.

Returns:

An Object[] of Serializable keys

getSize

public int getSize()

Returns the current store size.

Specified by:

getSize in interface Store

put

public void put(Element entry)
         throws java.io.IOException

Puts an item into the cache.

Specified by:

put in interface Store

Throws:

java.io.IOException

remove

public boolean remove(java.io.Serializable key)
               throws java.io.IOException

Removes an item from the cache.

Specified by:

remove in interface Store

Throws:

java.io.IOException

removeAll

public void removeAll()
               throws java.io.IOException

Removes all cached items from the cache.

Specified by:

removeAll in interface Store

Throws:

java.io.IOException

dispose

public void dispose()

Shuts down the disk store in preparation for cache shutdown

If a VM crash happens, the shutdown hook will not run. The data file and the index file will be out of synchronisation. At initialisation we always delete the index file after we have read the elements, so that it has a zero length. On a dirty restart, it still will have and the data file will automatically be deleted, thus preserving safety.

Specified by:

dispose in interface Store

isSpoolEmpty

public boolean isSpoolEmpty()

Whether there are any elements waiting to be spooled to disk.

Returns:

false if there are elements waiting, otherwise true

toString

public java.lang.String toString()

Returns a String representation of the DiskStore

getTotalFileSize

public long getTotalFileSize()

Returns:

the total size of the data file and the index file, in bytes.

getDataFileSize

public long getDataFileSize()

Returns:

the size of the data file in bytes.

calculateDataFileSparseness

public float calculateDataFileSparseness()

The design of the layout on the data file means that there will be small gaps created when DiskElements are reused.

Returns:

the sparseness, measured as the percentage of space in the Data File not used for holding data

getUsedDataSize

public long getUsedDataSize()

When elements are deleted, spaces are left in the file. These spaces are tracked and are reused when new elements need to be written.

This method indicates the actual size used for data, excluding holes. It can be compared with getDataFileSize() as a measure of fragmentation.

getIndexFileSize

public long getIndexFileSize()

Returns:

the size of the index file, in bytes.

getDataFileName

public java.lang.String getDataFileName()

Returns:

the file name of the data file where the disk store stores data, without any path information.

getDataFilePath

public java.lang.String getDataFilePath()

Returns:

the disk path, which will be dependent on the operating system

getIndexFileName

public java.lang.String getIndexFileName()

Returns:

the file name of the index file, which maintains a record of elements and their addresses on the data file, without any path information.

isExpiryThreadAlive

public boolean isExpiryThreadAlive()

The expiry thread is started provided the cache is not eternal

If started it will continue to run until the dispose() method is called, at which time it should be interrupted and then die.

Returns:

true if an expiryThread was created and is still alive.