Package com.tangosol.net.cache

Class SerializationCache

  • All Implemented Interfaces:
    CacheMap, ConfigurableCacheMap, ObservableMap, Map
    public class SerializationCache
extends AbstractSerializationCache
implements CacheMap, ConfigurableCacheMap
    A version of SerializationMap that implements an LRU policy.

    This implementation is partially thread safe. It assumes that multiple threads will not be accessing the same keys at the same time, nor would any other thread be accessing this cache while a clear() operation were going on, for example. In other words, this implementation assumes that access to this cache is either single-threaded or gated through an object like WrapperConcurrentMap.

    The primary reason why SerializationCache is a sub-class of SerializationMap instead of combining their functionality is that SerializationMap represents a passive store, and thus does not implement the ObservableMap interface, while SerializationCache represents an active store, and thus clients of it would have to always handle potential events, even if it were not size-limited.

    Since:
    Coherence 2.2
    Author:
    cp 2003.05.28

    • Field Detail

      • m_cMaxUnits

        protected long m_cMaxUnits
        Maximum number of units to manage in the cache.

      • m_cCurUnits

        protected long m_cCurUnits
        Current number of units to in the cache.

      • m_cPruneUnits

        protected long m_cPruneUnits
        The number of units to prune the cache down to.

      • m_nUnitFactor

        protected int m_nUnitFactor
        The unit factor.

    • Constructor Detail

      • SerializationCache

        public SerializationCache​(BinaryStore store,
                          int cMax)
        Construct a SerializationCache on top of a BinaryStore.
        Parameters:
        store - the BinaryStore to use to write the serialized objects to
        cMax - the maximum number of items to store in the binary store

      • SerializationCache

        public SerializationCache​(BinaryStore store,
                          int cMax,
                          ClassLoader loader)
        Construct a SerializationCache on top of a BinaryStore.
        Parameters:
        store - the BinaryStore to use to write the serialized objects to
        cMax - the maximum number of items to store in the binary store
        loader - the ClassLoader to use for deserialization

      • SerializationCache

        public SerializationCache​(BinaryStore store,
                          int cMax,
                          boolean fBinaryMap)
        Construct a SerializationCache on top of a BinaryStore.
        Parameters:
        store - the BinaryStore to use to write the serialized objects to
        cMax - the maximum number of items to store in the binary store
        fBinaryMap - true indicates that this map will only manage binary keys and values
        Since:
        Coherence 2.4

    • Method Detail

      • containsKey

        public boolean containsKey​(Object oKey)
        Returns true if this map contains a mapping for the specified key.
        Specified by:
        containsKey in interface Map
        Overrides:
        containsKey in class AbstractKeySetBasedMap
        Returns:
        true if this map contains a mapping for the specified key, false otherwise.

      • containsValue

        public boolean containsValue​(Object oValue)
        Returns true if this Map maps one or more keys to the specified value.
        Specified by:
        containsValue in interface Map
        Overrides:
        containsValue in class SerializationMap
        Returns:
        true if this Map maps one or more keys to the specified value, false otherwise

      • get

        public Object get​(Object oKey)
        Returns the value to which this map maps the specified key.
        Specified by:
        get in interface Map
        Overrides:
        get in class SerializationMap
        Parameters:
        oKey - the key object
        Returns:
        the value to which this map maps the specified key, or null if the map contains no mapping for this key

      • isEmpty

        public boolean isEmpty()
        Returns true if this map contains no key-value mappings.
        Specified by:
        isEmpty in interface Map
        Overrides:
        isEmpty in class AbstractKeySetBasedMap
        Returns:
        true if this map contains no key-value mappings

      • put

        public Object put​(Object oKey,
                  Object oValue)
        Associates the specified value with the specified key in this map.
        Specified by:
        put in interface CacheMap
        Specified by:
        put in interface Map
        Overrides:
        put in class AbstractSerializationCache
        Parameters:
        oKey - key with which the specified value is to be associated
        oValue - value to be associated with the specified key
        Returns:
        previous value associated with specified key, or null if there was no mapping for key

      • putAll

        public void putAll​(Map map)
        Copies all of the mappings from the specified map to this map. The effect of this call is equivalent to that of calling AbstractKeyBasedMap.put(K, V) on this map once for each mapping in the passed map. The behavior of this operation is unspecified if the passed map is modified while the operation is in progress.
        Specified by:
        putAll in interface Map
        Overrides:
        putAll in class AbstractSerializationCache
        Parameters:
        map - the Map containing the key/value pairings to put into this Map

      • remove

        public Object remove​(Object oKey)
        Removes the mapping for this key from this map if present. Expensive: updates both the underlying cache and the local cache.
        Specified by:
        remove in interface Map
        Overrides:
        remove in class AbstractSerializationCache
        Parameters:
        oKey - key whose mapping is to be removed from the map
        Returns:
        previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the map previously associated null with the specified key, if the implementation supports null values.

      • size

        public int size()
        Returns the number of key-value mappings in this map.
        Specified by:
        size in interface Map
        Overrides:
        size in class AbstractKeySetBasedMap
        Returns:
        the number of key-value mappings in this map

      • removeBlind

        protected boolean removeBlind​(Object oKey)
        Removes the mapping for this key from this map if present. This method exists to allow sub-classes to optimize remove functionality for situations in which the original value is not required.
        Overrides:
        removeBlind in class AbstractSerializationCache
        Parameters:
        oKey - key whose mapping is to be removed from the map
        Returns:
        true iff the Map changed as the result of this operation

      • put

        public Object put​(Object oKey,
                  Object oValue,
                  long cMillis)
        Associates the specified value with the specified key in this cache. If the cache previously contained a mapping for this key, the old value is replaced. This variation of the CacheMap.put(Object oKey, Object oValue) method allows the caller to specify an expiry (or "time to live") for the cache entry.
        Specified by:
        put in interface CacheMap
        Parameters:
        oKey - key with which the specified value is to be associated
        oValue - value to be associated with the specified key
        cMillis - the number of milliseconds until the cache entry will expire, also referred to as the entry's "time to live"; pass CacheMap.EXPIRY_DEFAULT to use the cache's default time-to-live setting; pass CacheMap.EXPIRY_NEVER to indicate that the cache entry should never expire; this milliseconds value is not a date/time value, such as is returned from System.currentTimeMillis()
        Returns:
        previous value associated with specified key, or null if there was no mapping for key. A null return can also indicate that the map previously associated null with the specified key, if the implementation supports null values

      • getUnits

        public int getUnits()
        Determine the number of units that the cache currently stores.

        Note: It is expected that the return type will be widened to a long in Coherence 4.

        Specified by:
        getUnits in interface ConfigurableCacheMap
        Returns:
        the current size of the cache in units

      • getHighUnits

        public int getHighUnits()
        Determine the limit of the cache size in units. The cache will prune itself automatically once it reaches its maximum unit level. This is often referred to as the "high water mark" of the cache.

        Note: It is expected that the return type will be widened to a long in Coherence 4.

        Specified by:
        getHighUnits in interface ConfigurableCacheMap
        Returns:
        the limit of the cache size in units

      • setHighUnits

        public void setHighUnits​(int cMax)
        Update the maximum size of the cache in units. This is often referred to as the "high water mark" of the cache.

        Note: It is expected that the parameter will be widened to a long in Coherence 4.

        Specified by:
        setHighUnits in interface ConfigurableCacheMap
        Parameters:
        cMax - the new maximum size of the cache, in units

      • getLowUnits

        public int getLowUnits()
        Determine the point to which the cache will shrink when it prunes. This is often referred to as a "low water mark" of the cache. If the cache incrementally prunes, then this setting will have no effect.

        Note: It is expected that the parameter will be widened to a long in Coherence 4.

        Specified by:
        getLowUnits in interface ConfigurableCacheMap
        Returns:
        the number of units that the cache prunes to

      • setLowUnits

        public void setLowUnits​(int cUnits)
        Specify the point to which the cache will shrink when it prunes. This is often referred to as a "low water mark" of the cache.

        Note: It is expected that the parameter will be widened to a long in Coherence 4.

        Specified by:
        setLowUnits in interface ConfigurableCacheMap
        Parameters:
        cUnits - the number of units that the cache prunes to

      • getUnitFactor

        public int getUnitFactor()
        Determine the factor by which the Units, LowUnits and HighUnits properties are adjusted. Using a binary unit calculator, for example, the factor 1048576 could be used to count megabytes instead of bytes.

        Note: This property exists only to avoid changing the type of the units, low units and high units properties from 32-bit values to 64-bit values. It is expected that the parameter will be dropped in Coherence 4.

        Specified by:
        getUnitFactor in interface ConfigurableCacheMap
        Returns:
        the units factor; the default is 1

      • setUnitFactor

        public void setUnitFactor​(int nFactor)
        Determine the factor by which the Units, LowUnits and HighUnits properties are adjusted. Using a binary unit calculator, for example, the factor 1048576 could be used to count megabytes instead of bytes.

        Note: This property exists only to avoid changing the type of the units, low units and high units properties from 32-bit values to 64-bit values. It is expected that the parameter will be dropped in Coherence 4.

        Specified by:
        setUnitFactor in interface ConfigurableCacheMap
        Parameters:
        nFactor - the units factor; the default is 1

      • evict

        public void evict​(Object oKey)
        Evict a specified key from the cache, as if it had expired from the cache. If the key is not in the cache, then the method has no effect.
        Specified by:
        evict in interface ConfigurableCacheMap
        Parameters:
        oKey - the key to evict from the cache

      • evictAll

        public void evictAll​(Collection colKeys)
        Evict the specified keys from the cache, as if they had each expired from the cache.

        The result of this method is defined to be semantically the same as the following implementation: 

        
 for (Iterator iter = colKeys.iterator(); iter.hasNext(); )
     {
     Object oKey = iter.next();
     evict(oKey);
     }

        Specified by:
        evictAll in interface ConfigurableCacheMap
        Parameters:
        colKeys - a collection of keys to evict from the cache

      • getExpiryDelay

        public int getExpiryDelay()
        Determine the default "time to live" for each individual cache entry.
        Specified by:
        getExpiryDelay in interface ConfigurableCacheMap
        Returns:
        the number of milliseconds that a cache entry value will live, or zero if cache entries are never automatically expired

      • setExpiryDelay

        public void setExpiryDelay​(int cMillis)
        Specify the default "time to live" for cache entries. This does not affect the already-scheduled expiry of existing entries.
        Specified by:
        setExpiryDelay in interface ConfigurableCacheMap
        Parameters:
        cMillis - the number of milliseconds that cache entries will live, or zero to disable automatic expiry

      • getNextExpiryTime

        public long getNextExpiryTime()
        Determine the next expiry time for the cache entries. This value is supposed to be used only by the "active" expiry algorithms, so for implementations that choose to return the value of zero the entries will be evicted as with pre-existing "passive" expiry approach.
        Specified by:
        getNextExpiryTime in interface ConfigurableCacheMap
        Returns:
        the earliest time (using the SafeClock) that one or more cache entries will expire or zero if the cache is empty, its entries never expire or the implementation chooses to avoid the pro-active eviction

      • flush

        public void flush()
        Deprecated.
        use evict()
        Flush items that have expired.

      • toString

        public String toString()
        Returns a string representation of this Map. The string representation consists of a list of key-value mappings in the order returned by the Map's entrySet view's iterator, enclosed in braces ("{}"). Adjacent mappings are separated by the characters ", " (comma and space). Each key-value mapping is rendered as the key followed by an equals sign ("=") followed by the associated value. Keys and values are converted to strings as by String.valueOf(Object).
        Overrides:
        toString in class SerializationMap
        Returns:
        a String representation of this Map

      • setBinaryStore

        protected void setBinaryStore​(BinaryStore store)
        Configures the BinaryStore that this map will use for its storage.
        Overrides:
        setBinaryStore in class SerializationMap
        Parameters:
        store - the BinaryStore to use

      • getTouchCounter

        protected long getTouchCounter()
        Determine the next value from the touch counter.
        Returns:
        the next value from the touch counter

      • getLruArray

        protected LongArray getLruArray()
        Get the LRU data structure. The key is a touch count, the value is the Object key for the cache.
        Returns:
        the the LRU data structure

      • getExpiryArray

        protected LongArray getExpiryArray()
        Get the Expiry data structure. The key is a date/time value, the value is a set of Object keys for the cache that expire at that time.
        Returns:
        the the Expiry data structure

      • registerKey

        protected void registerKey​(Object oKey,
                           Binary binKey,
                           Binary binValue)
        Register a new key for the SerializationMap. This method maintains the internal key Set for the SerializationMap.
        Overrides:
        registerKey in class SerializationMap
        Parameters:
        oKey - the key that has been added to the map
        binKey - the binary form of the key
        binValue - the binary form of the value

      • registerKey

        protected void registerKey​(Object oKey,
                           Binary binKey,
                           Binary binValue,
                           int cMillis)
        Register a new key for the SerializationMap. This method maintains the internal key Set for the SerializationMap.
        Parameters:
        oKey - the key that has been added to the map
        binKey - the binary form of the key (null if only TTL change)
        binValue - the binary form of the value (null if only TTL change)
        cMillis - the TTL value (in milliseconds) for the entry

      • touch

        protected void touch​(Object oKey)
        Touch an object to pop it to the top of the LRU
        Parameters:
        oKey - the key of the object to touch

      • unregisterKey

        protected void unregisterKey​(Object oKey)
        Unregister a key from the SerializationMap. This method maintains the internal key Set for the SerializationMap.
        Overrides:
        unregisterKey in class SerializationMap
        Parameters:
        oKey - the key that has been removed from the map

      • checkSize

        protected void checkSize()
        Make sure the size of the cache isn't too big.

      • checkExpiry

        protected void checkExpiry()
        Make sure that the cache does not contain expired items.

      • instantiateEntryAttributes

        public SerializationCache.EntryAttributes instantiateEntryAttributes​(SerializationCache.EntryAttributes attrOrig,
                                                                     long ldtExpires,
                                                                     long nTouch,
                                                                     int cUnits)
        Factory pattern: Construct an attribute holder for an entry.
        Parameters:
        attrOrig - the previous attributes for this entry, if any
        ldtExpires - the date/time at which the entry expires, or zero
        nTouch - the touch counter assigned to the entry
        cUnits - the number of storage units used by the entry
        Returns:
        the instantiated SerializationCache.EntryAttributes

      • instantiateEntrySet

        protected Set instantiateEntrySet()
        Factory pattern: Create a Set that represents the entries in the Map.
        Overrides:
        instantiateEntrySet in class AbstractKeySetBasedMap
        Returns:
        a new instance of Set that represents the entries in the Map