rabbit.cache
Class NCache<K,V>

java.lang.Object
  rabbit.cache.NCache<K,V>

Type Parameters:

K - the key type of the cache

V - the data resource

All Implemented Interfaces:

java.lang.Runnable, Cache<K,V>

public class NCache<K,V>
extends java.lang.Object
implements Cache<K,V>, java.lang.Runnable

The NCache is like a Map in lookup/insert/delete The NCache is persistent over sessions (saves itself to disk). The NCache is selfcleaning, that is it removes old stuff.

Author:

Robert Olofsson

Constructor Summary

NCache(SProperties props, FileHandler<K> fhk, FileHandler<V> fhv)
Create a cache that uses default values.

Method Summary

void	addEntry(CacheEntry<K,V> ent) Insert a CacheEntry into the cache.
void	clear() Clear the Cache from files.
void	entryChanged(CacheEntry<K,V> ent, K newKey, V newHook) Signal that a cache entry have changed.
void	flush() Make sure that the cache is written to the disk.
java.net.URL	getCacheDir() Get the location where this cache stores its files.
long	getCacheTime() Get the number of miliseconds the cache stores things usually.
int	getCleanLoopTime() Get how long time the cleaner sleeps between cleanups.
long	getCurrentSize() Get the current size of the cache
java.util.Collection<rabbit.cache.NCacheEntry<K,V>>	getEntries() Get the CacheEntries in the cache.
CacheEntry<K,V>	getEntry(K k) Get the CacheEntry assosiated with given object.
java.lang.String	getEntryName(long id, boolean real, java.lang.String extension) Get the file name for a cache entry.
FileHandler<V>	getHookFileHandler() Get the file handler for the values.
FileHandler<K>	getKeyFileHandler() Get the file handler for the keys.
java.util.logging.Logger	getLogger() Get the logger of this cache
long	getMaxSize() Get the maximum size for this cache.
long	getNumberOfEntries() Get the current number of entries in the cache.
CacheEntry<K,V>	newEntry(K k) Reserve space for a CacheEntry with key o.
void	remove(K k) Remove the Entry with key k from the cache.
void	run() Loop in a cleaning loop.
void	setCacheTime(long newCacheTime) Set the standard expiry-time for CacheEntries
void	setCleanLoopTime(int newCleanLoopTime) Set how long time the cleaner sleeps between cleanups.
void	setMaxSize(long newMaxSize) Set the maximum size for this cache.
void	setup(SProperties config) Configure the cache system from the given config.
void	startCleaner() Start the thread that cleans the cache.
void	stop() Stop this cache.

Methods inherited from class java.lang.Object

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

Constructor Detail

NCache

public NCache(SProperties props,
              FileHandler<K> fhk,
              FileHandler<V> fhv)
       throws java.io.IOException

Create a cache that uses default values. Note that you must call startCleaner to have the cache fully up.

Parameters:

props - the configuration of the cache

fhk - the FileHandler for the cache keys

fhv - the FileHandler for the cache values

Throws:

java.io.IOException - if the cache file directory can not be configured

Method Detail

startCleaner

public void startCleaner()

Start the thread that cleans the cache.

getCacheDir

public java.net.URL getCacheDir()

Description copied from interface: Cache

Get the location where this cache stores its files.

Specified by:

getCacheDir in interface Cache<K,V>

Returns:

the location, null if no physical location is used.

getMaxSize

public long getMaxSize()

Get the maximum size for this cache.

Specified by:

getMaxSize in interface Cache<K,V>

Returns:

the maximum size in bytes this cache.

setMaxSize

public void setMaxSize(long newMaxSize)

Set the maximum size for this cache.

Specified by:

setMaxSize in interface Cache<K,V>

Parameters:

newMaxSize - the new maximum size for the cache.

getCacheTime

public long getCacheTime()

Get the number of miliseconds the cache stores things usually. This is the standard expiretime for objects, but you can set it for CacheEntries individially if you want to. NOTE 1: dont trust that an object will be in the cache this long. NOTE 2: dont trust that an object will be removed from the cache when it expires.

Specified by:

getCacheTime in interface Cache<K,V>

Returns:

the number of miliseconds objects are stored normally.

setCacheTime

public void setCacheTime(long newCacheTime)

Set the standard expiry-time for CacheEntries

Specified by:

setCacheTime in interface Cache<K,V>

Parameters:

newCacheTime - the number of miliseconds to keep objects normally.

getCleanLoopTime

public int getCleanLoopTime()

Get how long time the cleaner sleeps between cleanups.

Returns:

the number of millis between cleanups

setCleanLoopTime

public void setCleanLoopTime(int newCleanLoopTime)

Set how long time the cleaner sleeps between cleanups.

Parameters:

newCleanLoopTime - the number of miliseconds to sleep.

getCurrentSize

public long getCurrentSize()

Get the current size of the cache

Specified by:

getCurrentSize in interface Cache<K,V>

Returns:

the current size of the cache in bytes.

getNumberOfEntries

public long getNumberOfEntries()

Get the current number of entries in the cache.

Specified by:

getNumberOfEntries in interface Cache<K,V>

Returns:

the current number of entries in the cache.

getEntry

public CacheEntry<K,V> getEntry(K k)
                         throws CacheException

Get the CacheEntry assosiated with given object.

Specified by:

getEntry in interface Cache<K,V>

Parameters:

k - the key.

Returns:

the CacheEntry or null (if not found).

Throws:

CacheException - upon failure to get the key

getEntryName

public java.lang.String getEntryName(long id,
                                     boolean real,
                                     java.lang.String extension)

Get the file name for a cache entry.

Specified by:

getEntryName in interface Cache<K,V>

Parameters:

id - the id of the cache entry

real - false if this is a temporary cache file, true if it is a realized entry.

extension - the cache entry extension.

Returns:

the file name of the new entry

newEntry

public CacheEntry<K,V> newEntry(K k)

Reserve space for a CacheEntry with key o.

Specified by:

newEntry in interface Cache<K,V>

Parameters:

k - the key for the CacheEntry.

Returns:

a new CacheEntry initialized for the cache.

getKeyFileHandler

public FileHandler<K> getKeyFileHandler()

Description copied from interface: Cache

Get the file handler for the keys.

Specified by:

getKeyFileHandler in interface Cache<K,V>

Returns:

the FileHandler for the key objects

getHookFileHandler

public FileHandler<V> getHookFileHandler()

Description copied from interface: Cache

Get the file handler for the values.

Specified by:

getHookFileHandler in interface Cache<K,V>

Returns:

the FileHandler for the values

addEntry

public void addEntry(CacheEntry<K,V> ent)
              throws CacheException

Insert a CacheEntry into the cache.

Specified by:

addEntry in interface Cache<K,V>

Parameters:

ent - the CacheEntry to store.

Throws:

CacheException - if adding the entry fails

entryChanged

public void entryChanged(CacheEntry<K,V> ent,
                         K newKey,
                         V newHook)
                  throws CacheException

Signal that a cache entry have changed.

Specified by:

entryChanged in interface Cache<K,V>

Parameters:

ent - the CacheEntry that changed

newKey - the new key of the entry

newHook - the new value

Throws:

CacheException - if updating the cache fails

remove

public void remove(K k)
            throws CacheException

Remove the Entry with key k from the cache.

Specified by:

remove in interface Cache<K,V>

Parameters:

k - the key for the CacheEntry.

Throws:

CacheException - if removal fails

clear

public void clear()
           throws CacheException

Clear the Cache from files.

Specified by:

clear in interface Cache<K,V>

Throws:

CacheException - if the clear operation failed

getEntries

public java.util.Collection<rabbit.cache.NCacheEntry<K,V>> getEntries()

Get the CacheEntries in the cache. Note! some entries may be invalid if you have a corruct cache.

Specified by:

getEntries in interface Cache<K,V>

Returns:

a Collection of the CacheEntries.

flush

public void flush()

Make sure that the cache is written to the disk.

Specified by:

flush in interface Cache<K,V>

run

public void run()

Loop in a cleaning loop.

Specified by:

run in interface java.lang.Runnable

stop

public void stop()

Description copied from interface: Cache

Stop this cache. If this cache is using any cleaner threads they have to be stopped when this method is called.

Specified by:

stop in interface Cache<K,V>

setup

public void setup(SProperties config)
           throws java.io.IOException

Configure the cache system from the given config.

Parameters:

config - the properties describing the cache settings.

Throws:

java.io.IOException - if the new cache can not be configured correctly

getLogger

public java.util.logging.Logger getLogger()

Description copied from interface: Cache

Get the logger of this cache

Specified by:

getLogger in interface Cache<K,V>

Returns:

the Logger used by the cache