Cocoon API: Class MemoryStore

org.apache.cocoon.store
Class MemoryStore

java.lang.Object
  |
  +--org.apache.cocoon.store.MemoryStore

All Implemented Interfaces:

Configurable, java.lang.Runnable, Status, Store

public class MemoryStore

extends java.lang.Object

implements Store, Status, Configurable, java.lang.Runnable

This class implements a memory-managed hashtable wrapper that uses a weighted mix of LRU and LFU to keep track of object importance. NOTE: this class is _HIGHLY_ un-optimized and this class is _CRITICAL_ for a fast performance of the whole system. So, if you find any better way to implement this class (clever data models, smart update algorithms, etc...), please, consider patching this implementation or sending a note about a method to do it.

Version:

$Revision: 1.15 $ $Date: 2001/01/16 22:35:01 $

Author:

Stefano Mazzocchi, Michel Lehon

Constructor Summary

MemoryStore()

Method Summary

boolean	containsKey(java.lang.Object key) Indicates if the given key is associated to a contained object.
void	free() Frees some of the fast memory used by this store.
java.lang.Object	get(java.lang.Object key) Get the object associated to the given unique key.
java.lang.String	getStatus() Returns the signature of this store implementation
long	getTime(java.lang.Object key) Gets the time this object was added.
void	hold(java.lang.Object key, java.lang.Object object) Holds the given object in a volatile state.
void	init(Configurations conf) Initialize the MemoryStore.
java.util.Enumeration	list() Returns the list of used keys.
boolean	memoryLow()
void	remove(java.lang.Object key) Remove the object associated to the given key and returns the object associated to the given key or null if not found.
void	run() Background memory check.
void	store(java.lang.Object key, java.lang.Object value) Store the given object in a persistent state.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

MemoryStore

public MemoryStore()

Method Detail

init

public void init(Configurations conf)
          throws InitializationException

Initialize the MemoryStore. A few options can be used :

• freememory = How much memory to keep free for normal jvm operation. (Default: 1 Mb)
• heapsize = The size of the heap before cleanup starts. (Default: 60 Mb)
• usethread = use a cleanup daemon thread. (Default: true)
• threadpriority = priority to run cleanup thread (1-10). (Default: 10)
• interval = time in seconds to sleep between memory checks (Default: 10 seconds)

Specified by:

init in interface Configurable

run

public void run()

Background memory check. Checks that memory is not running too low in the JVM because of the Store. It will try to keep overall memory usage below the requested levels.

Specified by:

run in interface java.lang.Runnable

memoryLow

public boolean memoryLow()

store

public void store(java.lang.Object key,
                  java.lang.Object value)

Store the given object in a persistent state. It is up to the caller to ensure that the key has a persistent state across different JVM executions.

Specified by:

store in interface Store

hold

public void hold(java.lang.Object key,
                 java.lang.Object object)

Holds the given object in a volatile state. This means the object store will discard held objects if the virtual machine is restarted or some error happens.

Specified by:

hold in interface Store

get

public java.lang.Object get(java.lang.Object key)

Get the object associated to the given unique key.

Specified by:

get in interface Store

getTime

public long getTime(java.lang.Object key)
             throws java.lang.NullPointerException

Gets the time this object was added.

Specified by:

getTime in interface Store

Throws:

java.lang.NullPointerException - if the object is not in the store.

remove

public void remove(java.lang.Object key)

Remove the object associated to the given key and returns the object associated to the given key or null if not found.

Specified by:

remove in interface Store

containsKey

public boolean containsKey(java.lang.Object key)

Indicates if the given key is associated to a contained object.

Specified by:

containsKey in interface Store

list

public java.util.Enumeration list()

Returns the list of used keys.

Specified by:

list in interface Store

free

public void free()

Frees some of the fast memory used by this store.

Specified by:

free in interface Store

getStatus

public java.lang.String getStatus()

Returns the signature of this store implementation

Specified by:

getStatus in interface Status