## com.sun.appserv.util.cache
Class LruCache

    java.lang.Object
      com.sun.appserv.util.cache.BaseCache
          com.sun.appserv.util.cache.LruCache

All Implemented Interfaces:
  Cache

    public class LruCache

extends BaseCache

LRUCache in-memory bounded cache with an LRU list

Nested Class Summary
`protected static class` `LruCache.LruCacheItem` default CacheItem class implementation

Nested classes/interfaces inherited from class com.sun.appserv.util.cache.BaseCache
`BaseCache.CacheItem`

Field Summary
`protected int` `defaultMaxEntries`
`protected LruCache.LruCacheItem` `head`
`protected boolean` `isUnbounded`
`protected int` `listSize`
`static long` `NO_TIMEOUT`
`protected LruCache.LruCacheItem` `tail`
`protected long` `timeout`
`protected int` `trimCount`

Fields inherited from class com.sun.appserv.util.cache.BaseCache
`_rb, bucketLocks, buckets, entryCount, listeners, maxBuckets, refreshFlags, threshold`

Constructor Summary
`LruCache()` default constructor
`LruCache(int defaultMaxEntries)` constructor with specified max entries.

Method Summary
`protected BaseCache.CacheItem` `createItem(int hashCode, Object key, Object value, int size)` create new item
`Object` `getStatByName(String key)` get the desired statistic counter
`Map` `getStats()` get the stats snapshot
`void` `init(int maxEntries, long timeout, float loadFactor, Properties props)` initialize the cache
`protected void` `itemAccessed(BaseCache.CacheItem item)` this item is accessed
`protected BaseCache.CacheItem` `itemAdded(BaseCache.CacheItem item)` /** this item is just added to the cache
`protected void` `itemRefreshed(BaseCache.CacheItem item, int oldSize)` item value has been refreshed
`protected void` `itemRemoved(BaseCache.CacheItem item)` item value has been removed from the cache
`void` `setTimeout(long timeout)` sets the timeout value
`void` `trimExpiredEntries(int maxCount)` trim the expired entries from the cache.
`protected BaseCache.CacheItem` `trimLru(long currentTime)` trim one item from the LRU list

Methods inherited from class com.sun.appserv.util.cache.BaseCache

`_put, _remove, _removeItem, add, add, addCacheListener, clear, clearStats, contains, decrementEntryCount, destroy, elements, eq, get, get, getAll, getEntryCount, getIndex, getIndex, handleOverflow, hash, incrementAddCount, incrementEntryCount, incrementHitCount, incrementMissCount, incrementOverflowCount, incrementRefreshCount, incrementRemovalCount, init, init, isEmpty, isThresholdReached, keys, loadValue, notifyRefresh, put, put, remove, remove, remove, removeAll, trimItem, values, waitRefresh`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### NO_TIMEOUT

    public static final long NO_TIMEOUT

See Also:
  Constant Field Values

### head

    protected LruCache.LruCacheItem head

### tail

    protected LruCache.LruCacheItem tail

### trimCount

    protected int trimCount

### listSize

    protected int listSize

### timeout

    protected long timeout

### defaultMaxEntries

    protected int defaultMaxEntries

### isUnbounded

    protected boolean isUnbounded

Constructor Detail

### LruCache

    public LruCache()

  default constructor

### LruCache

    public LruCache(int defaultMaxEntries)

  constructor with specified max entries.

  Parameters:
    `defaultMaxEntries` - specifies the default max entries to use when the maxEntries is <= 0.

Method Detail

### init

    public void init(int maxEntries,
                     long timeout,
                     float loadFactor,
                     Properties props)

  initialize the cache

  Parameters:
    `maxEntries` - maximum number of entries expected in the cache
    `loadFactor` - the load factor
    `timeout` - to be used to trim the expired entries
    `props` - opaque list of properties for a given cache implementation
  Throws:
    `a` - generic Exception if the initialization failed

### setTimeout

    public void setTimeout(long timeout)

  sets the timeout value

  Parameters:
    `timeout` - to be used to trim the expired entries

### createItem

    protected BaseCache.CacheItem createItem(int hashCode,
                                             Object key,
                                             Object value,
                                             int size)

  create new item

  Overrides:
    `createItem` in class `BaseCache`
  Parameters:
    `hashCode` - for the entry
    `key` - `Object` key
    `value` - `Object` value
    `size` - size in bytes of the item subclasses may override to provide their own CacheItem extensions e.g. one that permits persistence.

### trimLru

    protected BaseCache.CacheItem trimLru(long currentTime)

  trim one item from the LRU list

  Parameters:
    `currentTime` - of this operation
  Returns:
    the item trimmed from cache list synchronization is handled by the caller

### itemAdded

    protected BaseCache.CacheItem itemAdded(BaseCache.CacheItem item)

  /** this item is just added to the cache

  Overrides:
    `itemAdded` in class `BaseCache`
  Parameters:
    `item` - `CacheItem` that was created
  Returns:
    a overflow item; may be null this function checks if adding the new item results in a overflow; if so, it returns the item to be removed. Cache bucket is already synchronized by the caller

### itemAccessed

    protected void itemAccessed(BaseCache.CacheItem item)

  this item is accessed

  Overrides:
    `itemAccessed` in class `BaseCache`
  Parameters:
    `item` - `CacheItem` accessed Cache bucket is already synchronized by the caller

### itemRefreshed

    protected void itemRefreshed(BaseCache.CacheItem item,
                                 int oldSize)

  item value has been refreshed

  Overrides:
    `itemRefreshed` in class `BaseCache`
  Parameters:
    `item` - `CacheItem` that was refreshed
    `oldSize` - size of the previous value that was refreshed Cache bucket is already synchronized by the caller

### itemRemoved

    protected void itemRemoved(BaseCache.CacheItem item)

  item value has been removed from the cache

  Overrides:
    `itemRemoved` in class `BaseCache`
  Parameters:
    `item` - `CacheItem` that was just removed Cache bucket is already synchronized by the caller

### trimExpiredEntries

    public void trimExpiredEntries(int maxCount)

  trim the expired entries from the cache.

  Specified by:
    `trimExpiredEntries` in interface `Cache`
  Overrides:
    `trimExpiredEntries` in class `BaseCache`
  Parameters:
    `maxCount` - maximum number of invalid entries to trim specify Integer.MAX_VALUE to trim all invalid entries This call is to be scheduled by a thread managed by the container. NOTE: this algorithm assumes that all the entries in the cache have identical timeout (otherwise traversing from tail won't be right).

### getStatByName

    public Object getStatByName(String key)

  get the desired statistic counter

  Specified by:
    `getStatByName` in interface `Cache`
  Overrides:
    `getStatByName` in class `BaseCache`
  Parameters:
    `key` - to corresponding stat
  Returns:
    an Object corresponding to the stat See also: Constant.java for the key

### getStats

    public Map getStats()

  Description copied from class: `BaseCache`
  get the stats snapshot

  Specified by:
    `getStats` in interface `Cache`
  Overrides:
    `getStats` in class `BaseCache`
  Returns:
    a Map of stats See also: Constant.java for the keys

Copyright © 2008 Mort Bay Consulting. All Rights Reserved.