com.jdon.cache
类 UtilCache

java.lang.Object
  com.jdon.cache.UtilCache

public class UtilCache
extends Object

Generalized caching utility. Provides a number of caching features:

• Limited or unlimited element capacity
• If limited, removes elements with the LRU (Least Recently Used) algorithm
• Keeps track of when each element was loaded into the cache
• Using the expireTime can report whether a given element has expired
• Counts misses and hits

字段摘要

Map	cacheLineTable A hashtable containing a CacheLine object with a value and a loadTime for each element. for above jdk1.5
protected long	expireTime Specifies the amount of time since initial loading before an element will be reported as expired.
protected long	hitCount A count of the number of cache hits
ConcurrentLinkedList	keyLRUList A list of the elements order by Least Recent Use
protected long	maxSize The maximum number of elements in the cache.
protected long	missCount A count of the number of cache misses
static String	module
protected boolean	useSoftReference Specifies whether or not to use soft references for this cache, defaults to false

构造方法摘要

UtilCache(int maxSize, long expireTime, boolean useSoftReference)

UtilCache(PropsUtil propsUtil)
Default constructor, all members stay at default values as defined in cache.properties, or the defaults in this file if cache.properties is not found, or there are no 'default' entries in it.

方法摘要

void	clear() Removes all elements from this cache
void	clearAllCaches() Removes all elements from this cache
void	clearCounters() Clears the hit and miss counters
void	clearExpired() Clears all expired cache entries; also clear any cache entries where the SoftReference in the CacheLine object has been cleared by the gc
boolean	containsKey(Object key) Returns a boolean specifying whether or not an element with the specified key is in the cache.
Object	get(Object key) Gets an element from the cache according to the specified key.
long	getExpireTime() return the current expire time for the cache elements
long	getHitCount() Returns the number of successful hits on the cache
long	getMaxSize() Returns the current maximum number of elements in the cache
long	getMissCount() Returns the number of cache misses
boolean	getUseSoftReference() Return whether or not the cache lines should use a soft reference to the data
protected boolean	hasExpired(CacheLine line)
boolean	hasExpired(Object key) Returns a boolean specifying whether or not the element corresponding to the key has expired.
Set	keySet()
void	put(Object key, Object value) Puts or loads the passed element into the cache
void	remove(Object key) Removes an element from the cache according to the specified key
void	setExpireTime(long expireTime) Sets the expire time for the cache elements.
void	setMaxSize(long maxSize) Sets the maximum number of elements in the cache.
protected void	setPropertiesParams(PropsUtil propsUtil, String cacheName)
long	size() Returns the number of elements currently in the cache
void	startMon(long expireTime)
void	stop()
Collection	values()

从类 java.lang.Object 继承的方法

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

字段详细信息

module

public static String module

keyLRUList

public final ConcurrentLinkedList keyLRUList

A list of the elements order by Least Recent Use

cacheLineTable

public final Map cacheLineTable

A hashtable containing a CacheLine object with a value and a loadTime for each element. for above jdk1.5

hitCount

protected volatile long hitCount

A count of the number of cache hits

missCount

protected volatile long missCount

A count of the number of cache misses

maxSize

protected volatile long maxSize

The maximum number of elements in the cache. If set to 0, there will be no limit on the number of elements in the cache.

expireTime

protected volatile long expireTime

Specifies the amount of time since initial loading before an element will be reported as expired. If set to 0, elements will never expire.

useSoftReference

protected volatile boolean useSoftReference

Specifies whether or not to use soft references for this cache, defaults to false

构造方法详细信息

UtilCache

public UtilCache(PropsUtil propsUtil)

Default constructor, all members stay at default values as defined in cache.properties, or the defaults in this file if cache.properties is not found, or there are no 'default' entries in it.

UtilCache

public UtilCache(int maxSize,
                 long expireTime,
                 boolean useSoftReference)

方法详细信息

startMon

public void startMon(long expireTime)

setPropertiesParams

protected void setPropertiesParams(PropsUtil propsUtil,
                                   String cacheName)

put

public void put(Object key,
                Object value)

Puts or loads the passed element into the cache

参数：

key - The key for the element, used to reference it in the hastables and LRU linked list

value - The value of the element

get

public Object get(Object key)

Gets an element from the cache according to the specified key. If the requested element hasExpired, it is removed before it is looked up which causes the function to return null.

参数：

key - The key for the element, used to reference it in the hastables and LRU linked list

返回：

The value of the element specified by the key

remove

public void remove(Object key)

Removes an element from the cache according to the specified key

参数：

key - The key for the element, used to reference it in the hastables and LRU linked list

keySet

public Set keySet()

values

public Collection values()

clear

public void clear()

Removes all elements from this cache

clearAllCaches

public void clearAllCaches()

Removes all elements from this cache

getHitCount

public long getHitCount()

Returns the number of successful hits on the cache

返回：

The number of successful cache hits

getMissCount

public long getMissCount()

Returns the number of cache misses

返回：

The number of cache misses

clearCounters

public void clearCounters()

Clears the hit and miss counters

setMaxSize

public void setMaxSize(long maxSize)

Sets the maximum number of elements in the cache. If 0, there is no maximum.

参数：

maxSize - The maximum number of elements in the cache

getMaxSize

public long getMaxSize()

Returns the current maximum number of elements in the cache

返回：

The maximum number of elements in the cache

setExpireTime

public void setExpireTime(long expireTime)

Sets the expire time for the cache elements. If 0, elements never expire.

参数：

expireTime - The expire time for the cache elements

getExpireTime

public long getExpireTime()

return the current expire time for the cache elements

返回：

The expire time for the cache elements

getUseSoftReference

public boolean getUseSoftReference()

Return whether or not the cache lines should use a soft reference to the data

size

public long size()

Returns the number of elements currently in the cache

返回：

The number of elements currently in the cache

containsKey

public boolean containsKey(Object key)

Returns a boolean specifying whether or not an element with the specified key is in the cache. If the requested element hasExpired, it is removed before it is looked up which causes the function to return false.

参数：

key - The key for the element, used to reference it in the hastables and LRU linked list

返回：

True is the cache contains an element corresponding to the specified key, otherwise false

hasExpired

public boolean hasExpired(Object key)

Returns a boolean specifying whether or not the element corresponding to the key has expired. Only returns true if element is in cache and has expired. Error conditions return false, if no expireTable entry, returns true. Always returns false if expireTime <= 0. Also, if SoftReference in the CacheLine object has been cleared by the gc return true.

参数：

key - The key for the element, used to reference it in the hastables and LRU linked list

返回：

True is the element corresponding to the specified key has expired, otherwise false

hasExpired

protected boolean hasExpired(CacheLine line)

clearExpired

public void clearExpired()

Clears all expired cache entries; also clear any cache entries where the SoftReference in the CacheLine object has been cleared by the gc

stop

public void stop()