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:
Iterable<Cache.Entry<K,V>>
All Known Subinterfaces:
PersistentUserManagedCache<K,V>, UserManagedCache<K,V>
public interface Cache<K,V> extends 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

    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.
    Map<K,V>
    getAll(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.
    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(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(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 Details

    • 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:
      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:
      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:
      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:
      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

      Map<K,V> getAll(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:
      NullPointerException - if the Set or any of the contained keys are null.
      BulkCacheLoadingException - if loading some or all values failed

    • putAll

      void putAll(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:
      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(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:
      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:
      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:
      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:
      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:
      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

    • getRuntimeConfiguration

      CacheRuntimeConfiguration<K,V> getRuntimeConfiguration()
      Exposes the CacheRuntimeConfiguration associated with this Cache instance.
      Returns:
      the configuration currently in use

    • iterator

      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 Iterable<K>
      Returns:
      an Iterator over the cache entries.