org.nerd4j.utils.cache

Class AbstractCacheProvider<V>

java.lang.Object

org.nerd4j.utils.cache.AbstractCacheProvider<V>

Type Parameters:

V - type of data in the cache entry.

All Implemented Interfaces:

CacheProvider<V>

Direct Known Subclasses:

EmptyCacheProvider, HeapCacheProvider

public abstract class AbstractCacheProvider<V>
extends Object
implements CacheProvider<V>

Abstract implementation of the CacheProvider interface that implements all the common checks and logic allowing the extending classes to implement only the underlying caching system related logic.

Since:

2.0.0

Author:

Massimo Coluzzi

Field Summary

Fields

Modifier and Type	Field and Description
static Logger	logger Logging system.

Constructor Summary

Constructors

Constructor and Description
AbstractCacheProvider() Default constructor.

Method Summary

Modifier and Type	Method and Description
void	clear() Removes all elements from the cache.
protected abstract void	doClear() Removes all keys and related entries from the cache.
protected abstract CacheEntry<V>	doGet(CacheKey key) Returns the cache entry related to the given key.
protected abstract void	doPut(CacheKey key, CacheEntry<V> entry, long duration) Binds the given entry to the given key and put it into the underlying cache.
protected abstract void	doRemove(CacheKey key) Removes the given key and the related entry from the cache.
protected abstract boolean	doTouch(CacheKey key, long duration) Defers the expiration time of the cache entry related to the given key.
CacheEntry<V>	get(CacheKey key) Returns the cache entry related to the given key.
protected CacheEntry<V>	getEntry(V value, long duration) Returns a new cache entry with the given value that will expire after the given amount of milliseconds
void	put(CacheKey key, V value, long duration) Inserts the given key and the related value into the cache.
void	remove(CacheKey key) Removes the given key from the cache.
boolean	touch(CacheKey key, long duration) Defers the expiration time of the entry related to the given key.

Methods inherited from class java.lang.Object

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

Field Detail

logger

public static final Logger logger

Logging system.

By default the logging level is Level.WARNING and will only log exceptions.

If you want to log any caching operation you need to set the logging level to Level.INFO.

If you want to dig into deeper detail about cache loading and updating operations, including the data that is going to be cached, you need to set the logging level to Level.FINE.

If you trust this class to work properly and you do not want your logs to get dirty you can turn off this log by setting the logging level to Level.OFF.

To change the Logger levels and outputs follow the Java documentation.

Constructor Detail

AbstractCacheProvider

public AbstractCacheProvider()

Default constructor.

Method Detail

get

public CacheEntry<V> get(CacheKey key)

Returns the cache entry related to the given key.

If the given key is never been cached null will be returned, otherwise an object of type CacheEntry will be returned containing the related value and expiration time. The value in the CacheEntry can be null.

Specified by:

get in interface CacheProvider<V>

Parameters:

key - the key to search for.

Returns:

the related entry if present, null otherwise.

put

public void put(CacheKey key,
                V value,
                long duration)

Inserts the given key and the related value into the cache.

If the given key is already present, the related CacheEntry will be replaced.

The duration is expressed in milliseconds. If the duration is 0 or less nothing will be done.

Specified by:

put in interface CacheProvider<V>

Parameters:

key - key to be cached.

value - value to be cached.

duration - the amount of time the value will last in cache.

touch

public boolean touch(CacheKey key,
                     long duration)

Defers the expiration time of the entry related to the given key.

If the key is not present a CacheProviderException will be thrown.

The duration is expressed in milliseconds. If the duration is 0 or less nothing will be done.

Specified by:

touch in interface CacheProvider<V>

Parameters:

key - the key to search for.

duration - number of milliseconds until expiration.

Returns:

true if the operation was successful, @code false} otherwise.

remove

public void remove(CacheKey key)

Removes the given key from the cache.

If the key is not present nothing will be done.

Specified by:

remove in interface CacheProvider<V>

Parameters:

key - the key to be removed.

clear

public void clear()

Removes all elements from the cache.

This method will clear the underlying cache.

Specified by:

clear in interface CacheProvider<V>

getEntry

protected CacheEntry<V> getEntry(V value,
                                 long duration)

Returns a new cache entry with the given value that will expire after the given amount of milliseconds

Parameters:

value - the value to put into the cache entry.

duration - the amount of milliseconds before expiration.

Returns:

the new cache entry

doGet

protected abstract CacheEntry<V> doGet(CacheKey key)
                                throws Exception

Returns the cache entry related to the given key.

If the given key was never being cached null will be returned, otherwise will be returned a CacheEntry containing the cached value and the expiration time.

Parameters:

key - the cache key to search for.

Returns:

the entry related to the given key if any, null otherwise.

Throws:

Exception - if the method execution fails.

doPut

protected abstract void doPut(CacheKey key,
                              CacheEntry<V> entry,
                              long duration)
                       throws Exception

Binds the given entry to the given key and put it into the underlying cache.

If the given key is already present into the cache will be replaced.

Parameters:

key - key to be cached.

entry - entry to be cached.

duration - number of milliseconds until expiration.

Throws:

Exception - if the method execution fails.

doTouch

protected abstract boolean doTouch(CacheKey key,
                                   long duration)
                            throws Exception

Defers the expiration time of the cache entry related to the given key.

If no entry is present for the given key a RequirementFailure should be thrown.

Only the first thread calling this method for the given key should be successful, any other thread should fail. This method returns true if the operation was successful and false otherwise.

Parameters:

key - key to update.

duration - number of milliseconds until expiration.

Returns:

true if the related entry has been updated.

Throws:

Exception - if the method execution fails.

doRemove

protected abstract void doRemove(CacheKey key)
                          throws Exception

Removes the given key and the related entry from the cache.

If the key is not present nothing will be done.

Parameters:

key - key to be removed.

Throws:

Exception - if the method execution fails.

doClear

protected abstract void doClear()
                         throws Exception

Removes all keys and related entries from the cache.

If cache is already empty nothing will be done.

Throws:

Exception - if the method execution fails.