Package org.ehcache

Interface Cache<K,​V>

  • Type Parameters:
    K - the key type for the cache
    V - the value type for the cache
    All Superinterfaces:
    java.lang.Iterable<Cache.Entry<K,​V>>
    All Known Subinterfaces:
    PersistentUserManagedCache<K,​V>, UserManagedCache<K,​V>
    public interface Cache<K,​V>
extends java.lang.Iterable<Cache.Entry<K,​V>>
    Defines all operational methods to create, access, update and delete mappings of key to value.

    In order to function, cache keys must respect the hash code and equals contracts. This contract is what will be used to lookup values based on key.

    A Cache is not a map, mostly because it has the following two concepts linked to mappings:

    • Eviction: A Cache has a capacity constraint and in order to honor it, a Cache can evict (remove) a mapping at any point in time. Note that eviction may occur before maximum capacity is reached.
    • Expiry: Data in a Cache can be configured to expire after some time. There is no way for a Cache user to differentiate from the API between a mapping being absent or expired.

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Interface Description
      static interface  Cache.Entry<K,​V>
      A mapping of key to value held in a Cache.

    • Method Summary

      All Methods Instance Methods Abstract Methods 
      Modifier and Type Method Description
      void clear()
      Removes all mappings currently present in the Cache.
      boolean containsKey​(K key)
      Checks whether a mapping for the given key is present, without retrieving the associated value.
      V get​(K key)
      Retrieves the value currently mapped to the provided key.
      java.util.Map<K,​V> getAll​(java.util.Set<? extends K> keys)
      Retrieves all values associated with the given key set.
      CacheRuntimeConfiguration<K,​V> getRuntimeConfiguration()
      Exposes the CacheRuntimeConfiguration associated with this Cache instance.
      java.util.Iterator<Cache.Entry<K,​V>> iterator()
      Returns an iterator over the cache entries.
      void put​(K key, V value)
      Associates the given value to the given key in this Cache.
      void putAll​(java.util.Map<? extends K,​? extends V> entries)
      Associates all the provided key:value pairs.
      V putIfAbsent​(K key, V value)
      Maps the specified key to the specified value in this cache, unless a non-expired mapping already exists.
      void remove​(K key)
      Removes the value, if any, associated with the provided key.
      boolean remove​(K key, V value)
      Removes the entry for a key only if currently mapped to the given value and the entry is not expired.
      void removeAll​(java.util.Set<? extends K> keys)
      Removes any associated value for the given key set.
      V replace​(K key, V value)
      Replaces the entry for a key only if currently mapped to some value and the entry is not expired.
      boolean replace​(K key, V oldValue, V newValue)
      Replaces the entry for a key only if currently mapped to the given value and the entry is not expired.

      • Methods inherited from interface java.lang.Iterable

        forEach, spliterator

    • Method Detail

      • get

        V get​(K key)
throws CacheLoadingException
        Retrieves the value currently mapped to the provided key.
        Parameters:
        key - the key, may not be null
        Returns:
        the value mapped to the key, null if none
        Throws:
        java.lang.NullPointerException - if the provided key is null
        CacheLoadingException - if the CacheLoaderWriter associated with this cache was invoked and threw an Exception

      • put

        void put​(K key,
         V value)
  throws CacheWritingException
        Associates the given value to the given key in this Cache.
        Parameters:
        key - the key, may not be null
        value - the value, may not be null
        Throws:
        java.lang.NullPointerException - if either key or value is null
        CacheWritingException - if the CacheLoaderWriter associated with this cache threw an Exception while writing the value for the given key to the underlying system of record.

      • containsKey

        boolean containsKey​(K key)
        Checks whether a mapping for the given key is present, without retrieving the associated value.
        Parameters:
        key - the key, may not be null
        Returns:
        true if a mapping is present, false otherwise
        Throws:
        java.lang.NullPointerException - if the provided key is null

      • remove

        void remove​(K key)
     throws CacheWritingException
        Removes the value, if any, associated with the provided key.
        Parameters:
        key - the key to remove the value for, may not be null
        Throws:
        java.lang.NullPointerException - if the provided key is null
        CacheWritingException - if the CacheLoaderWriter associated with this cache threw an Exception while removing the value for the given key from the underlying system of record.

      • getAll

        java.util.Map<K,​V> getAll​(java.util.Set<? extends K> keys)
                         throws BulkCacheLoadingException
        Retrieves all values associated with the given key set.
        Parameters:
        keys - keys to query for, may not contain null
        Returns:
        a map from keys to values or null if the key was not mapped
        Throws:
        java.lang.NullPointerException - if the Set or any of the contained keys are null.
        BulkCacheLoadingException - if loading some or all values failed

      • putAll

        void putAll​(java.util.Map<? extends K,​? extends V> entries)
     throws BulkCacheWritingException
        Associates all the provided key:value pairs.
        Parameters:
        entries - key:value pairs to associate, keys or values may not be null
        Throws:
        java.lang.NullPointerException - if the Map or any of the contained keys or values are null.
        BulkCacheWritingException - if the CacheLoaderWriter associated with this cache threw an Exception while writing given key:value pairs to the underlying system of record.

      • removeAll

        void removeAll​(java.util.Set<? extends K> keys)
        throws BulkCacheWritingException
        Removes any associated value for the given key set.
        Parameters:
        keys - keys to remove values for, may not be null
        Throws:
        java.lang.NullPointerException - if the Set or any of the contained keys are null.
        BulkCacheWritingException - if the CacheLoaderWriter associated with this cache threw an Exception while removing mappings for given keys from the underlying system of record.

      • clear

        void clear()
        Removes all mappings currently present in the Cache.

        It does so without invoking the CacheLoaderWriter or any registered CacheEventListener instances. This is not an atomic operation and can potentially be very expensive.

      • putIfAbsent

        V putIfAbsent​(K key,
              V value)
       throws CacheLoadingException,
              CacheWritingException
        Maps the specified key to the specified value in this cache, unless a non-expired mapping already exists.

        This is equivalent to 

           if (!cache.containsKey(key))
       cache.put(key, value);
       return null;
   else
       return cache.get(key);
        except that the action is performed atomically.

        The value can be retrieved by calling the get method with a key that is equal to the original key.

        Neither the key nor the value can be null.

        Parameters:
        key - key with which the specified value is to be associated
        value - value to be associated with the specified key
        Returns:
        the value to which the specified key was previously mapped, or null if no such mapping existed or the mapping was expired
        Throws:
        java.lang.NullPointerException - if any of the arguments is null
        CacheWritingException - if the CacheLoaderWriter associated with this cache threw an Exception while writing the value for the given key to the underlying system of record.
        CacheLoadingException - if the CacheLoaderWriter associated with this cache was invoked and threw an Exception

      • remove

        boolean remove​(K key,
               V value)
        throws CacheWritingException
        Removes the entry for a key only if currently mapped to the given value and the entry is not expired.

        This is equivalent to 

           if (cache.containsKey(key) && cache.get(key).equals(value)) {
       cache.remove(key);
       return true;
   } else return false;
        except that the action is performed atomically.

        The key cannot be null.

        Parameters:
        key - key with which the specified value is associated
        value - value expected to be removed
        Returns:
        true if the value was successfully removed
        Throws:
        java.lang.NullPointerException - if any of the arguments is null
        CacheWritingException - if the CacheLoaderWriter associated with this cache threw an Exception while removing the value for the given key from the underlying system of record.

      • replace

        V replace​(K key,
          V value)
   throws CacheLoadingException,
          CacheWritingException
        Replaces the entry for a key only if currently mapped to some value and the entry is not expired.

        This is equivalent to 

           V oldValue = cache.get(key);
   if (oldValue != null) {
     cache.put(key, value);
   }
   return oldValue;
        except that the action is performed atomically.

        Neither the key nor the value can be null.

        Parameters:
        key - of the value to be replaced
        value - the new value
        Returns:
        the existing value that was associated with the key, or null if no such mapping existed or the mapping was expired
        Throws:
        java.lang.NullPointerException - if any of the arguments is null
        CacheWritingException - if the CacheLoaderWriter associated with this cache threw an Exception while writing the value for the given key to the underlying system of record.
        CacheLoadingException - if the CacheLoaderWriter associated with this cache was invoked and threw an Exception

      • replace

        boolean replace​(K key,
                V oldValue,
                V newValue)
         throws CacheLoadingException,
                CacheWritingException
        Replaces the entry for a key only if currently mapped to the given value and the entry is not expired.

        This is equivalent to 

           if (cache.containsKey(key) && cache.get(key).equals(oldValue)) {
       cache.put(key, newValue);
       return true;
   } else return false;
        except that the action is performed atomically.

        Neither the key nor the value can be null.

        Parameters:
        key - key with which the specified value is associated
        oldValue - value expected to be associated with the specified key
        newValue - value to be associated with the specified key
        Returns:
        true if the oldValue was successfully replaced by the newValue
        Throws:
        java.lang.NullPointerException - if any of the arguments is null
        CacheWritingException - if the CacheLoaderWriter associated with this cache threw an Exception while writing the value for the given key to the underlying system of record.
        CacheLoadingException - if the CacheLoaderWriter associated with this cache was invoked and threw an Exception

      • iterator

        java.util.Iterator<Cache.Entry<K,​V>> iterator()
        Returns an iterator over the cache entries.

        Due to the interactions of the cache and iterator contracts it is possible for iteration to return expired entries.

        Specified by:
        iterator in interface java.lang.Iterable<K>
        Returns:
        an Iterator over the cache entries.