Package com.tangosol.util

Class WrapperConcurrentMap<K,​V>

  • All Implemented Interfaces:
    ConcurrentMap<K,​V>, ObservableMap<K,​V>, Map<K,​V>
    Direct Known Subclasses:
    WrapperNamedCache
    public class WrapperConcurrentMap<K,​V>
extends WrapperObservableMap<K,​V>
implements ConcurrentMap<K,​V>
    A simple implementation of ConcurrentMap interface built as a wrapper around any Map implementation. As a subclass of WrapperObservableMap, it naturally implements the ObservableMap interface and provides an implementation of CacheStatistics interface.
    Author:
    gg 2002.04.02

    • Field Detail

      • m_fEnforceLocking

        protected boolean m_fEnforceLocking
        Flag indicating whether or not the locking is enforced for put, remove and clear operations.

      • m_cWaitMillis

        protected long m_cWaitMillis
        The number of milliseconds to continue trying to obtain a lock in case when the locking is enforced.

      • m_mapLock

        protected final SafeHashMap m_mapLock
        The map containing all the locks.

      • m_gateMap

        protected final Gate m_gateMap
        The ThreadGate object for the entire map.

    • Constructor Detail

      • WrapperConcurrentMap

        public WrapperConcurrentMap​(Map<K,​V> map)
        Construct a ConcurrentMap wrapper based on the specified map with locking enforced for put, remove and clear operations.

        Note: it is assumed that while the WrapperConcurrentMap exists, there is no direct manipulation with the content of the wrapped map.

        Parameters:
        map - the Map that will be wrapped by this WrapperConcurrentMap

      • WrapperConcurrentMap

        public WrapperConcurrentMap​(Map<K,​V> map,
                            boolean fEnforceLocking,
                            long cWaitMillis)
        Construct a ConcurrentMap wrapper based on the specified map.

        Note: it is assumed that while the WrapperConcurrentMap exists, there is no direct manipulation with the content of the wrapped map.

        Parameters:
        map - the Map that will be wrapped by this WrapperConcurrentMap
        fEnforceLocking - if true the locking is enforced for put, remove and clear operations; otherwise a client is responsible for calling lock and unlock explicitly
        cWaitMillis - if locking enforcement is required then this parameter specifies the number of milliseconds to continue trying to obtain a lock; pass -1 to block the calling thread until the lock could be obtained

    • Method Detail

      • lock

        public boolean lock​(Object oKey,
                    long cWait)
        Attempt to lock the specified item within the specified period of time.

        The item doesn't have to exist to be locked. While the item is locked there is known to be a lock holder which has an exclusive right to modify (calling put and remove methods) that item.

        Lock holder is an abstract concept that depends on the ConcurrentMap implementation. For example, holder could be a cluster member or a thread (or both).

        Locking strategy may vary for concrete implementations as well. Lock could have an expiration time (this lock is sometimes called a "lease") or be held indefinitely (until the lock holder terminates).

        Some implementations may allow the entire map to be locked. If the map is locked in such a way, then only a lock holder is allowed to perform any of the "put" or "remove" operations. Pass the special constant ConcurrentMap.LOCK_ALL as the oKey parameter to indicate the map lock.

        Specified by:
        lock in interface ConcurrentMap<K,​V>
        Parameters:
        oKey - key being locked
        cWait - the number of milliseconds to continue trying to obtain a lock; pass zero to return immediately; pass -1 to block the calling thread until the lock could be obtained
        Returns:
        true if the item was successfully locked within the specified time; false otherwise

      • lock

        public boolean lock​(Object oKey)
        Attempt to lock the specified item and return immediately.

        This method behaves exactly as if it simply performs the call lock(oKey, 0).

        Specified by:
        lock in interface ConcurrentMap<K,​V>
        Parameters:
        oKey - key being locked
        Returns:
        true if the item was successfully locked; false otherwise

      • unlock

        public boolean unlock​(Object oKey)
        Unlock the specified item. The item doesn't have to exist to be unlocked. If the item is currently locked, only the holder of the lock could successfully unlock it.
        Specified by:
        unlock in interface ConcurrentMap<K,​V>
        Parameters:
        oKey - key being unlocked
        Returns:
        true if the item was successfully unlocked; false otherwise

      • clear

        public void clear()
        Clear all key/value mappings.

        If lock enforcement is required an attempt will be made to lock the entire map using the ConcurrentMap.LOCK_ALL object.

        Note: if this operation fails due to a ConcurrentModificationException, then any subset of the current mappings could still remain in the map.

        Specified by:
        clear in interface ConcurrentMap<K,​V>
        Specified by:
        clear in interface Map<K,​V>
        Overrides:
        clear in class WrapperObservableMap<K,​V>
        Throws:
        ConcurrentModificationException - if any entry is locked by another thread

      • put

        public V put​(K oKey,
             V oValue)
        Associates the specified value with the specified key in this map.
        Specified by:
        put in interface ConcurrentMap<K,​V>
        Specified by:
        put in interface Map<K,​V>
        Overrides:
        put in class WrapperObservableMap<K,​V>
        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
        Throws:
        ConcurrentModificationException - if the entry is locked by another thread

      • putAll

        public void putAll​(Map<? extends K,​? extends V> 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 ConcurrentMap<K,​V>
        Specified by:
        putAll in interface Map<K,​V>
        Overrides:
        putAll in class WrapperObservableMap<K,​V>
        Parameters:
        map - the Map containing the key/value pairings to put into this Map
        Throws:
        ConcurrentModificationException - if the entry is locked by another thread

      • remove

        public V 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 ConcurrentMap<K,​V>
        Specified by:
        remove in interface Map<K,​V>
        Overrides:
        remove in class WrapperObservableMap<K,​V>
        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.
        Throws:
        ConcurrentModificationException - if the entry is locked by another thread

      • 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 WrapperObservableMap<K,​V>
        Parameters:
        oKey - key whose mapping is to be removed from the map
        Returns:
        true iff the Map changed as the result of this operation
        Throws:
        ConcurrentModificationException - if the entry is locked by another thread

      • 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 WrapperObservableMap<K,​V>
        Returns:
        a String representation of this Map

      • isLockingEnforced

        public boolean isLockingEnforced()
        Obtain the flag indicating whether or not the locking is enforced for put, remove and clear operations.
        Returns:
        true if locking is enforced; false otherwise

      • setLockingEnforced

        public void setLockingEnforced​(boolean fEnforce)
        Set the flag indicating whether or not the locking is enforced for put, remove and clear operations.
        Parameters:
        fEnforce - pass true to enforce locking; false otherwise

      • getWaitMillis

        public long getWaitMillis()
        Return the number of milliseconds to continue trying to obtain a lock in case when the locking is enforced.
        Returns:
        the wait time in milliseconds

      • setWaitMillis

        public void setWaitMillis​(long cWaitMillis)
        Specify the number of milliseconds to continue trying to obtain a lock in case when the locking is enforced.
        Parameters:
        cWaitMillis - the wait time in milliseconds

      • getLockDescription

        public String getLockDescription​(Object oKey)
        Make a human-readable description of the information kept about the passed key.
        Parameters:
        oKey - the key
        Returns:
        the information known about the passed key

      • instantiateLock

        protected WrapperConcurrentMap.Lock instantiateLock​(Object oKey)
        Factory pattern.
        Parameters:
        oKey - the key
        Returns:
        a new instance of the Lock class (or a subclass thereof)