Cache (MMBase2 Utils 2.0.0

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

All Implemented Interfaces:

Map<K,V>, CacheMBean, SizeMeasurable

Direct Known Subclasses:

BlobCache, FactoryCache, ResultCache, TemplateCache
```
public abstract class Cache<K,V>
extends Object
implements SizeMeasurable, Map<K,V>, CacheMBean
```
A base class for all Caches. Extend this class for other caches.

Version:

$Id$

Author:

Michiel Meeuwissen

Nested Class Summary
- Nested classes/interfaces inherited from interface java.util.Map
  Map.Entry<K,V>

Field Summary

Fields
Modifier and Type Field and Description

protected Object lock

protected int maxEntrySize

Fields
Modifier and Type	Field and Description
`protected Object`	`lock`
`protected int`	`maxEntrySize`

Constructor Summary

Constructors
Constructor and Description

Cache(int size)

Constructors
Constructor and Description
`Cache(int size)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`protected boolean`	`checkCachePolicy(Object key)` Checks whether the key object should be cached.
`void`	`clear()`
`void`	`configure(Element cacheElement)`
`boolean`	`contains(Object key)`
`boolean`	`containsKey(Object key)`
`boolean`	`containsValue(Object value)`
`Set<Map.Entry<K,V>>`	`entrySet()`
`boolean`	`equals(Object o)`
`V`	`get(Object key)` Like 'get' of Maps but considers if the cache is active or not, and the cache policy of the key.
`double`	`getAverageValueLength()` Returns the average 'length' of the values in the cache.
`int`	`getByteSize()` Determines the byte-size of this object
`int`	`getByteSize(SizeOf sizeof)` Determines the byte-size of this object using the given SizeOf instance.
`int`	`getCheapByteSize()` Returns the sum of bytesizes of every key and value.
`int`	`getCount(K key)`
`protected int`	`getDefaultMaxEntrySize()` This has to be overridden by Caches which support max entry size.
`String`	`getDescription()` Gives a description for this cache type.
`long`	`getHits()` Returns the number of times an element was succesfully retrieved from the table.
`Class<?>`	`getImplementation()`
`Object`	`getLock()` If you want to structurally modify this cache, synchronize on this object.
`int`	`getMaxEntrySize()` Return the maximum entry size for the cache in bytes.
`int`	`getMaxSize()`
`long`	`getMisses()` Returns the number of times an element cpould not be retrieved from the table.
`String`	`getName()` Returns a name for this cache type.
`long`	`getPuts()` Returns the number of times an element was committed to the table.
`double`	`getRatio()` Returns the ratio of hits and misses.
`int`	`getSize()`
`String`	`getStats()` Returns statistics on this table.
`int`	`hashCode()`
`boolean`	`isActive()` Wether this cache is active or not.
`boolean`	`isEmpty()`
`Set<K>`	`keySet()`
`int`	`maxSize()`
`V`	`put(K key, V value)` Like 'put' of LRUHashtable but considers if the cache is active or not.
`void`	`putAll(Map<? extends K,? extends V> t)`
`Cache<K,V>`	`putCache()` Puts this cache in the caches repository.
`V`	`remove(Object key)`
`void`	`reset()` Reset 'puts', 'misses' and 'puts' to 0.
`void`	`setActive(boolean a)` Sets this cache to active or passive.
`(package private) void`	`setImplementation(String clazz, Map<String,String> configValues)`
`void`	`setMaxEntrySize(int i)`
`void`	`setMaxSize(int size)`
`int`	`size()`
`String`	`toString()`
`Collection<V>`	`values()`

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

Methods inherited from interface java.util.Map
compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, putIfAbsent, remove, replace, replace, replaceAll

- Field Detail
  - maxEntrySize
```
protected int maxEntrySize
```
  - lock
```
protected volatile Object lock
```
- Constructor Detail
  - Cache
```
public Cache(int size)
```
- Method Detail
  - setImplementation
```
void setImplementation(String clazz,
                       Map<String,String> configValues)
```
  - getLock
```
public final Object getLock()
```
    If you want to structurally modify this cache, synchronize on this object.
    
    Since:
    
    MMBase-1.8.6
  - getName
```
public String getName()
```
    Returns a name for this cache type. Default it is the class name, but this normally will be overriden.
    
    Specified by:
    
    getName in interface CacheMBean
  - getDescription
```
public String getDescription()
```
    Gives a description for this cache type. This can be used in cache overviews.
    
    Specified by:
    
    getDescription in interface CacheMBean
  - getMaxEntrySize
```
public int getMaxEntrySize()
```
    Return the maximum entry size for the cache in bytes. If the cache-type supports it (default no), then no values bigger then this will be stored in the cache.
    
    Specified by:
    
    getMaxEntrySize in interface CacheMBean
    
    See Also:
    
    getMaxEntrySize()
  - setMaxEntrySize
```
public void setMaxEntrySize(int i)
```
    Specified by:
    
    setMaxEntrySize in interface CacheMBean
    
    Since:
    
    MMBase-1.9.2
    
    See Also:
    
    setMaxEntrySize(int)
  - getAverageValueLength
```
public double getAverageValueLength()
```
    Returns the average 'length' of the values in the cache. Whatever that may mean. A natural meaning may be the length of the cached lists. May return NaN if unknown or undetermined.
    
    Specified by:
    
    getAverageValueLength in interface CacheMBean
    
    Since:
    
    MMBase-1.9.2
  - getDefaultMaxEntrySize
```
protected int getDefaultMaxEntrySize()
```
    This has to be overridden by Caches which support max entry size.
  - entrySet
```
public Set<Map.Entry<K,V>> entrySet()
```
    Specified by:
    
    entrySet in interface Map<K,V>
  - getImplementation
```
public Class<?> getImplementation()
```
    Since:
    
    MMBase-1.8.6
  - checkCachePolicy
```
protected boolean checkCachePolicy(Object key)
```
    Checks whether the key object should be cached. This method returns false if either the current cache is inactive, or the object to cache has a cache policy associated that prohibits caching of the object.
    
    Parameters:
    
    key - the object to be cached
    
    Returns:
    
    true if the object can be cached
    
    Since:
    
    MMBase-1.8
  - get
```
public V get(Object key)
```
    Like 'get' of Maps but considers if the cache is active or not, and the cache policy of the key.
    
    Specified by:
    
    get in interface Map<K,V>
  - put
```
public V put(K key,
             V value)
```
    Like 'put' of LRUHashtable but considers if the cache is active or not.
    
    Specified by:
    
    put in interface Map<K,V>
  - getHits
```
public long getHits()
```
    Returns the number of times an element was succesfully retrieved from the table.
    
    Specified by:
    
    getHits in interface CacheMBean
    
    See Also:
    
    getHits()
  - getMisses
```
public long getMisses()
```
    Returns the number of times an element cpould not be retrieved from the table.
    
    Specified by:
    
    getMisses in interface CacheMBean
    
    See Also:
    
    getMisses()
  - getPuts
```
public long getPuts()
```
    Returns the number of times an element was committed to the table.
    
    Specified by:
    
    getPuts in interface CacheMBean
    
    See Also:
    
    getPuts()
  - reset
```
public void reset()
```
    Reset 'puts', 'misses' and 'puts' to 0.
    
    Specified by:
    
    reset in interface CacheMBean
    
    Since:
    
    MMBase-1.9.2
    
    See Also:
    
    reset()
  - setMaxSize
```
public void setMaxSize(int size)
```
    Specified by:
    
    setMaxSize in interface CacheMBean
  - maxSize
```
public int maxSize()
```
  - getMaxSize
```
public int getMaxSize()
```
    Specified by:
    
    getMaxSize in interface CacheMBean
    
    See Also:
    
    getMaxSize()
  - size
```
public int size()
```
    Specified by:
    
    size in interface Map<K,V>
    
    See Also:
    
    Map.size()
  - getSize
```
public int getSize()
```
    Specified by:
    
    getSize in interface CacheMBean
    
    See Also:
    
    getSize()
  - contains
```
public boolean contains(Object key)
```
  - getCount
```
public int getCount(K key)
```
  - getRatio
```
public double getRatio()
```
    Returns the ratio of hits and misses. The higher the ratio, the more succesfull the table retrieval is. A value of 1 means every attempt to retrieve data is succesfull, while a value nearing 0 means most times the object requested it is not available. Generally a high ratio means the table can be shrunk, while a low ratio means its size needs to be increased.
    
    Specified by:
    
    getRatio in interface CacheMBean
    
    Returns:
    
    A double between 0 and 1 or NaN.
    
    See Also:
    
    getRatio()
  - getStats
```
public String getStats()
```
    Returns statistics on this table. The information shown includes number of accesses, ratio of misses and hits, current size, and number of puts.
  - setActive
```
public void setActive(boolean a)
```
    Sets this cache to active or passive. TODO: Writing back to caches.xml if necessary (if this call was nog caused by change of caches.xml itself)
    
    Specified by:
    
    setActive in interface CacheMBean
    
    See Also:
    
    isActive()
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object
  - isActive
```
public final boolean isActive()
```
    Wether this cache is active or not.
    
    Specified by:
    
    isActive in interface CacheMBean
  - getByteSize
```
public int getByteSize()
```
    Description copied from interface: SizeMeasurable
    
    Determines the byte-size of this object
    
    Specified by:
    
    getByteSize in interface CacheMBean
    
    Specified by:
    
    getByteSize in interface SizeMeasurable
  - getByteSize
```
public int getByteSize(SizeOf sizeof)
```
    Description copied from interface: SizeMeasurable
    
    Determines the byte-size of this object using the given SizeOf instance. A SizeOf instance stores a Set already counted objects. So this method is typically called by SizeOf itself (recursion).
    
    Specified by:
    
    getByteSize in interface SizeMeasurable
  - getCheapByteSize
```
public int getCheapByteSize()
```
    Returns the sum of bytesizes of every key and value. This may count too much, because objects (like Nodes) may occur in more then one value, but this is considerably cheaper then getByteSize(), which has to keep a Collection of every counted object.
    
    Since:
    
    MMBase-1.8
  - clear
```
public void clear()
```
    Specified by:
    
    clear in interface Map<K,V>
    
    Specified by:
    
    clear in interface CacheMBean
    
    See Also:
    
    Map.clear()
  - containsKey
```
public boolean containsKey(Object key)
```
    Specified by:
    
    containsKey in interface Map<K,V>
    
    See Also:
    
    Map.containsKey(java.lang.Object)
  - containsValue
```
public boolean containsValue(Object value)
```
    Specified by:
    
    containsValue in interface Map<K,V>
    
    See Also:
    
    Map.containsValue(java.lang.Object)
  - equals
```
public boolean equals(Object o)
```
    Specified by:
    
    equals in interface Map<K,V>
    
    Overrides:
    
    equals in class Object
    
    See Also:
    
    Map.equals(java.lang.Object)
  - hashCode
```
public int hashCode()
```
    Specified by:
    
    hashCode in interface Map<K,V>
    
    Overrides:
    
    hashCode in class Object
    
    See Also:
    
    Map.hashCode()
  - isEmpty
```
public boolean isEmpty()
```
    Specified by:
    
    isEmpty in interface Map<K,V>
    
    See Also:
    
    Map.isEmpty()
  - keySet
```
public Set<K> keySet()
```
    Specified by:
    
    keySet in interface Map<K,V>
    
    See Also:
    
    Map.keySet()
  - putAll
```
public void putAll(Map<? extends K,? extends V> t)
```
    Specified by:
    
    putAll in interface Map<K,V>
    
    See Also:
    
    Map.putAll(java.util.Map)
  - remove
```
public V remove(Object key)
```
    Specified by:
    
    remove in interface Map<K,V>
    
    See Also:
    
    Map.remove(java.lang.Object)
  - values
```
public Collection<V> values()
```
    Specified by:
    
    values in interface Map<K,V>
    
    See Also:
    
    Map.values()
  - putCache
```
public Cache<K,V> putCache()
```
    Puts this cache in the caches repository.
    
    See Also:
    
    CacheManager.putCache(Cache)
  - configure
```
public void configure(Element cacheElement)
```
    Since:
    
    MMBase-2.0

Class Cache<K,V>

Nested Class Summary

Nested classes/interfaces inherited from interface java.util.Map

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface java.util.Map

Field Detail

maxEntrySize

lock

Constructor Detail

Cache

Method Detail

setImplementation

getLock

getName

getDescription

getMaxEntrySize

setMaxEntrySize

getAverageValueLength

getDefaultMaxEntrySize

entrySet

getImplementation

checkCachePolicy

get

put

getHits

getMisses

getPuts

reset

setMaxSize

maxSize

getMaxSize

size

getSize

contains

getCount

getRatio

getStats

setActive

toString

isActive

getByteSize

getByteSize

getCheapByteSize

clear

containsKey

containsValue

equals

hashCode

isEmpty

keySet

putAll

remove

values

putCache

configure