Package org.ofbiz.core.util

Class UtilCache<K,V>

java.lang.Object
org.ofbiz.core.util.UtilCache<K,V>
public class UtilCache<K,V> 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
Since:
2.0
Version:
$Revision: 1.1 $
Author:
David E. Jones

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    static class 
    UtilCache.CacheLine<T>
     

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    Map<K,UtilCache.CacheLine<V>>
    cacheLineTable
    A hashtable containing a CacheLine object with a value and a loadTime for each element.
    protected static Map<String,Integer>
    defaultIndices
    An index number appended to utilCacheTable names when there are conflicts.
    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
    LinkedList<K>
    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
    protected String
    name
    The name of the UtilCache instance, is also the key for the instance in utilCacheTable.
    protected boolean
    useSoftReference
    Specifies whether or not to use soft references for this cache, defaults to false
    static Map<String,UtilCache<?,?>>
    utilCacheTable
    A static Map to keep track of all of the UtilCache instances.

  • Constructor Summary

    Constructors
    Constructor
    Description
    UtilCache()
    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(long maxSize, long expireTime)
    Constructor which specifies the maxSize and expireTime.
    UtilCache(String cacheName)
    This constructor takes a name for the cache, puts itself in the utilCacheTable.
    UtilCache(String cacheName, long maxSize, long expireTime)
    Constructor which specifies the cacheName as well as the maxSize and expireTime.
    UtilCache(String cacheName, long maxSize, long expireTime, boolean useSoftReference)
    Constructor which specifies the cacheName as well as the maxSize, expireTime and useSoftReference.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    clear()
    Removes all elements from this cache
    static 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
    static void
    clearExpiredFromAllCaches()
    Clears all expired cache entries from all caches
    boolean
    containsKey(Object key)
    Returns a boolean specifying whether or not an element with the specified key is in the cache.
    V
    get(K 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
    String
    getName()
    Getter for the name of the UtilCache instance.
    protected String
    getNextDefaultIndex(String cacheName)
     
    boolean
    getUseSoftReference()
    Return whether or not the cache lines should use a soft reference to the data
    boolean
    hasExpired(K key)
    Returns a boolean specifying whether or not the element corresponding to the key has expired.
    protected boolean
    hasExpired(UtilCache.CacheLine<V> line)
     
    void
    put(K key, V value)
    Puts or loads the passed element into the cache
    Object
    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(String cacheName)
     
    void
    setUseSoftReference(boolean useSoftReference)
    Set whether or not the cache lines should use a soft reference to the data
    long
    size()
    Returns the number of elements currently in the cache
    static boolean
    validKey(String cacheName, Object key)
    Checks for a non-expired key in a specific cache

    Methods inherited from class java.lang.Object

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

  • Field Details

    • utilCacheTable

      public static Map<String,UtilCache<?,?>> utilCacheTable
      A static Map to keep track of all of the UtilCache instances.

    • defaultIndices

      protected static Map<String,Integer> defaultIndices
      An index number appended to utilCacheTable names when there are conflicts.

    • name

      protected String name
      The name of the UtilCache instance, is also the key for the instance in utilCacheTable.

    • keyLRUList

      public LinkedList<K> keyLRUList
      A list of the elements order by Least Recent Use

    • cacheLineTable

      public Map<K,UtilCache.CacheLine<V>> cacheLineTable
      A hashtable containing a CacheLine object with a value and a loadTime for each element.

    • hitCount

      protected long hitCount
      A count of the number of cache hits

    • missCount

      protected long missCount
      A count of the number of cache misses

    • maxSize

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

  • Constructor Details

    • UtilCache

      public UtilCache(String cacheName, long maxSize, long expireTime, boolean useSoftReference)
      Constructor which specifies the cacheName as well as the maxSize, expireTime and useSoftReference. The passed maxSize, expireTime and useSoftReference will be overridden by values from cache.properties if found.
      Parameters:
      maxSize - The maxSize member is set to this value
      expireTime - The expireTime member is set to this value
      cacheName - The name of the cache.
      useSoftReference - Specifies whether or not to use soft references for this cache.

    • UtilCache

      public UtilCache(String cacheName, long maxSize, long expireTime)
      Constructor which specifies the cacheName as well as the maxSize and expireTime. The passed maxSize and expireTime will be overridden by values from cache.properties if found.
      Parameters:
      maxSize - The maxSize member is set to this value
      expireTime - The expireTime member is set to this value
      cacheName - The name of the cache.

    • UtilCache

      public UtilCache(long maxSize, long expireTime)
      Constructor which specifies the maxSize and expireTime.
      Parameters:
      maxSize - The maxSize member is set to this value
      expireTime - The expireTime member is set to this value

    • UtilCache

      public UtilCache(String cacheName)
      This constructor takes a name for the cache, puts itself in the utilCacheTable. It also uses the cacheName to lookup the initialization parameters from cache.properties.
      Parameters:
      cacheName - The name of the cache.

    • UtilCache

      public UtilCache()
      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.

  • Method Details

    • getNextDefaultIndex

      protected String getNextDefaultIndex(String cacheName)

    • setPropertiesParams

      protected void setPropertiesParams(String cacheName)

    • put

      public void put(K key, V value)
      Puts or loads the passed element into the cache
      Parameters:
      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 V get(K 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.
      Parameters:
      key - The key for the element, used to reference it in the hastables and LRU linked list
      Returns:
      The value of the element specified by the key

    • remove

      public Object remove(Object key)
      Removes an element from the cache according to the specified key
      Parameters:
      key - The key for the element, used to reference it in the hastables and LRU linked list
      Returns:
      The value of the removed element specified by the key

    • clear

      public void clear()
      Removes all elements from this cache

    • clearAllCaches

      public static void clearAllCaches()
      Removes all elements from this cache

    • getName

      public String getName()
      Getter for the name of the UtilCache instance.
      Returns:
      The name of the instance

    • getHitCount

      public long getHitCount()
      Returns the number of successful hits on the cache
      Returns:
      The number of successful cache hits

    • getMissCount

      public long getMissCount()
      Returns the number of cache misses
      Returns:
      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.
      Parameters:
      maxSize - The maximum number of elements in the cache

    • getMaxSize

      public long getMaxSize()
      Returns the current maximum number of elements in the cache
      Returns:
      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.
      Parameters:
      expireTime - The expire time for the cache elements

    • getExpireTime

      public long getExpireTime()
      return the current expire time for the cache elements
      Returns:
      The expire time for the cache elements

    • setUseSoftReference

      public void setUseSoftReference(boolean useSoftReference)
      Set whether or not the cache lines should use a soft reference to the data

    • 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
      Returns:
      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.
      Parameters:
      key - The key for the element, used to reference it in the hastables and LRU linked list
      Returns:
      True is the cache contains an element corresponding to the specified key, otherwise false

    • hasExpired

      public boolean hasExpired(K 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.
      Parameters:
      key - The key for the element, used to reference it in the hastables and LRU linked list
      Returns:
      True is the element corresponding to the specified key has expired, otherwise false

    • hasExpired

      protected boolean hasExpired(UtilCache.CacheLine<V> 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

    • clearExpiredFromAllCaches

      public static void clearExpiredFromAllCaches()
      Clears all expired cache entries from all caches

    • validKey

      public static boolean validKey(String cacheName, Object key)
      Checks for a non-expired key in a specific cache