Package 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

  • Field Details

    • NO_TIMEOUT

      public static final long NO_TIMEOUT
      See Also:

    • 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 Details

    • 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 Details

    • 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