Cache (Jahia Server Implementation 8.0.0.0 API)

java.lang.Object
- org.jahia.services.cache.Cache<K,V>

All Implemented Interfaces:

CacheStatistics
```
public class Cache<K,V>
extends Object
implements CacheStatistics
```
This is the root class for all the cache in Jahia.

This cache can handle synchronization messages with other Jahia server instances by using JMS messages. This synchronization is automatically initialized and used when the JMS synchronization is activated in the Jahia configuration file.

Each cache must has a distinct name, and the associated description is only for debugging purpose or for monitoring display. Each cache uses a MRU (Most Recent Used) list to determine which elements will be removed from the cache when the cache limit has been reached. In this case, the least used cache entry will be removed.

Each object inserted in the cache will be wrapped into a CacheEntry instance, which contains among other information, the entry's expiration date and last accessed date.

Using the getCacheEntry method will retrieve the cache entry instance and not the object stored into the entry instance. To access the stored object instance, the get method should be used instead or use the getter methods of the CacheEntry class.

Caches can only be retrieved and created through the CacheFactory class, which is responsible for managing all the caches.

Since:

Jahia 4.0

Author:

Fulco Houkes

See Also:

CacheFactory, CacheEntry

Constructor Summary

Constructors
Modifier Constructor and Description

protected Cache(String name, CacheImplementation<K,CacheEntry<V>> cacheImplementation)
Creates a new Cache instance.

Constructors
Modifier	Constructor and Description
`protected`	`Cache(String name, CacheImplementation<K,CacheEntry<V>> cacheImplementation)` Creates a new `Cache` instance.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`boolean`	`containsKey(K entryKey)` Checks if the specified `entryKey` is present in the cache.
`void`	`flush()` Flushs all the cache entries.
`void`	`flush(boolean propagate)` Flushs all the cache entries.
`void`	`flushGroup(String groupName)`
`V`	`get(K entryKey)` Fetchs the cache entry associated to the `entryKey` and returns the object stored in fetched cache entry.
`double`	`getCacheEfficiency()` Retrieves the percentage of cache hit that could successfully be served.
`CacheEntry<V>`	`getCacheEntry(K entryKey)` Retrieve the cache entry associated to the `entryKey` argument or `null` when the requested cache entry is not available, or when the `entryKey` argument is `null`.
`CacheImplementation<K,CacheEntry<V>>`	`getCacheImplementation()`
`long`	`getGroupsKeysTotal()` Get the total number of keys in all the groups of this cache.
`long`	`getGroupsSize()` Get the number of groups for this cache.
`Collection<K>`	`getKeys()` Returns a Collection of all cache keys at the moment (may change in the next moment) Warning, if expiration times were set, they are NOT checked by this method, so make sure you perform a get and check that it is not null when using this method.
`String`	`getName()` Retrieves the cache name.
`long`	`getSuccessHits()` Retrieves the number of cache hits that could successfully be served.
`long`	`getTotalHits()` Retrieves the total number of cache hits.
`boolean`	`isEmpty()` Return true if there are no entries in the cache.
`void`	`put(K entryKey, V entryObj)` Add a new object into the cache.
`void`	`put(K entryKey, V entryObj, boolean propagate)` Add a new object into the cache.
`void`	`putCacheEntry(K entryKey, CacheEntry<V> entry, boolean propagate)` Add a new entry into the cache.
`void`	`remove(K entryKey)` Removes the cache entry associate to the key `entryKey`.
`int`	`size()` Return the current number of entries in the cache.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - Cache
```
protected Cache(String name,
                CacheImplementation<K,CacheEntry<V>> cacheImplementation)
```
    Creates a new Cache instance.
    
    Parameters:
    
    name - the cache name
- Method Detail
  - getCacheEntry
```
public CacheEntry<V> getCacheEntry(K entryKey)
```
    Retrieve the cache entry associated to the entryKey argument or null when the requested cache entry is not available, or when the entryKey argument is null.
    
    The last accessed date of the returned cache entry will be updated to the current date (& time) and it's set as the most recent used entry in the cache's MRU list. Expired cache entries will automatically be removed from the cache and null will be returned as result.
    
    Parameters:
    
    entryKey - the cache entry key. null keys will return null.
    
    Returns:
    
    the reference to the cache entry
  - get
```
public V get(K entryKey)
```
    Fetchs the cache entry associated to the entryKey and returns the object stored in fetched cache entry. null is returned when the entryKey is null, or when no cache entry could be found for the specified entryKey.
    
    Parameters:
    
    entryKey - the key associated to the requested object. A null key will return in a null result.
    
    Returns:
    
    the object associated to the code entryKey cache entry.
  - put
```
public void put(K entryKey,
                V entryObj)
```
    Add a new object into the cache. This method encapsulates automatically the specified entryObj object into a new CacheEntry instance and associated the new cache entry to the entryKey key. If there is already an entry associated with the entryKey key in the cache, that entry will be removed and replaced with the new specified entry.
    
    Parameters:
    
    entryKey - the object's associated key, null is not allowed
    
    entryObj - the reference to the object to be cached.
  - put
```
public void put(K entryKey,
                V entryObj,
                boolean propagate)
```
    Add a new object into the cache. This method encapsulates automatically the specified entryObj object into a new CacheEntry instance and associated the new cache entry to the entryKey key. If there is already an entry associated with the entryKey key in the cache, that entry will be removed and replaced with the new specified entry.
    
    Parameters:
    
    entryKey - the object's associated key, null is not allowed
    
    entryObj - the reference to the object to be cached.
    
    propagate - specifies whether the cache update should be sent across the cluster. If you don't know what this means, set it to true. Set it to false it you want to update the cache ONLY locally, for example when implementing a cache listener method.
  - putCacheEntry
```
public void putCacheEntry(K entryKey,
                          CacheEntry<V> entry,
                          boolean propagate)
```
    Add a new entry into the cache.
    
    The process will be ignored when either entryKey and/or entry is/are null. If there is already an entry associated with the entryKey key in the cache, that entry will be removed and replaced with the new specified entry.
    
    Parameters:
    
    entryKey - the cache entry key, null is not allowed.
    
    entry - the reference to the entry to be cached, null is not allowed.
    
    propagate - specifies whether the cache update should be sent across the cluster. If you don't know what this means, set it to true. Set it to false it you want to update the cache ONLY locally, for example when implementing a cache listener method.
  - remove
```
public void remove(K entryKey)
```
    Removes the cache entry associate to the key entryKey. The removal operation is canceled in case the entryKey is null; does nothing when the entryKey is unknown in the cache.
    
    Parameters:
    
    entryKey - the cache entry key, null is not allowed
  - isEmpty
```
public final boolean isEmpty()
```
    Return true if there are no entries in the cache.
    
    Returns:
    
    true when the cache is empty
  - size
```
public final int size()
```
    Return the current number of entries in the cache.
    
    Returns:
    
    the current cache size
  - getGroupsSize
```
public final long getGroupsSize()
```
    Get the number of groups for this cache. This is an approximate value as it is not synchronized.
    
    Returns:
    
    a long representing the number of elements in the cache groups LRUMap.
  - getGroupsKeysTotal
```
public final long getGroupsKeysTotal()
```
    Get the total number of keys in all the groups of this cache. This is an approximate value as it is not cached.
    
    Returns:
    
    a long representing the number of keys in all the groups.
  - getName
```
public final String getName()
```
    Retrieves the cache name.
    
    Returns:
    
    the cache region name
  - flush
```
public final void flush()
```
    Flushs all the cache entries. By sending the flushing event to all the cache's listeners.
  - flush
```
public void flush(boolean propagate)
```
    Flushs all the cache entries. When sendToListeners is true, the event is send to the cache's listeners.
  - flushGroup
```
public final void flushGroup(String groupName)
```
  - getSuccessHits
```
public final long getSuccessHits()
```
    Description copied from interface: CacheStatistics
    
    Retrieves the number of cache hits that could successfully be served.
    
    Specified by:
    
    getSuccessHits in interface CacheStatistics
    
    Returns:
    
    the number of cache hits that could successfully be served
  - getTotalHits
```
public final long getTotalHits()
```
    Description copied from interface: CacheStatistics
    
    Retrieves the total number of cache hits.
    
    Specified by:
    
    getTotalHits in interface CacheStatistics
    
    Returns:
    
    the number of cache hits
  - getCacheEfficiency
```
public double getCacheEfficiency()
```
    Description copied from interface: CacheStatistics
    
    Retrieves the percentage of cache hit that could successfully be served. This efficiency is useful for tuning the maximum cache size. Cache size should be changed increased for low efficiency percentages.
    
    Specified by:
    
    getCacheEfficiency in interface CacheStatistics
    
    Returns:
    
    the percentage of cache hit that could successfully be served
  - containsKey
```
public final boolean containsKey(K entryKey)
```
    Checks if the specified entryKey is present in the cache.
    
    Parameters:
    
    entryKey - the entry key to be checked.
    
    Returns:
    
    true when the entry key is present in the cache, otherwise return false
  - getKeys
```
public final Collection<K> getKeys()
```
    Returns a Collection of all cache keys at the moment (may change in the next moment) Warning, if expiration times were set, they are NOT checked by this method, so make sure you perform a get and check that it is not null when using this method.
    
    Returns:
    
    Collection of key objects in the cache
  - getCacheImplementation
```
public CacheImplementation<K,CacheEntry<V>> getCacheImplementation()
```

Class Cache<K,V>

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

Cache

Method Detail

getCacheEntry

get

put

put

putCacheEntry

remove

isEmpty

size

getGroupsSize

getGroupsKeysTotal

getName

flush

flush

flushGroup

getSuccessHits

getTotalHits

getCacheEfficiency

containsKey

getKeys

getCacheImplementation