ojb.broker.cache
Class ObjectCacheDefaultImpl

java.lang.Object
  |
  +--ojb.broker.cache.ObjectCacheDefaultImpl

All Implemented Interfaces:

ObjectCache

public class ObjectCacheDefaultImpl

extends java.lang.Object

implements ObjectCache

The ObjectCache stores all Objects loaded by the PersistenceBroker from a DB. When the PersistenceBroker tries to get an Object by its Primary key values it first lookups the cache if the object has been already loaded and cached. Using an ObjectCache has several advantages: - it increases performance as it reduces DB lookups. - it allows to perform circular lookups (as by crossreferenced objects) that would result in non-terminating loops without such a cache. - it maintains the uniqueness of objects as any Db row will be mapped to exactly one object. The cache uses soft-references which allows objects (softly) referenced by the cache to be reclaimed by the Java Garbage Collector when they are not longer referenced elsewhere.

Author:

Thomas Mahler

Field Summary

protected java.util.Hashtable

objectTable the hashtable holding all cached object

Constructor Summary

ObjectCacheDefaultImpl()
public Default Constructor

Method Summary

void	cache(Identity oid, java.lang.Object obj) makes object persistent to the Objectcache.
void	cache(java.lang.Object obj) Make object obj persistent to Objectcache.
void	clear() clear ObjectCache.
void	finalize()
java.lang.Object	lookup(Identity oid) Lookup object with Identity oid in objectTable.
void	remove(java.lang.Object obj) removes an Object from the cache.

Methods inherited from class java.lang.Object

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

Field Detail

objectTable

protected java.util.Hashtable objectTable

the hashtable holding all cached object

Constructor Detail

ObjectCacheDefaultImpl

public ObjectCacheDefaultImpl()

public Default Constructor

Method Detail

cache

public void cache(java.lang.Object obj)
           throws ClassNotPersistenceCapableException

Make object obj persistent to Objectcache. compute objects identity and use it as key for the hashmap

Specified by:

cache in interface ObjectCache

ClassNotPersistenceCapableException

clear

public void clear()

clear ObjectCache. I.e. remove all entries for classes and objects.

Specified by:

clear in interface ObjectCache

cache

public void cache(Identity oid,
                  java.lang.Object obj)

makes object persistent to the Objectcache. I'm using soft-references to allow gc reclaim unused objects even if they are still cached.

Specified by:

cache in interface ObjectCache

lookup

public java.lang.Object lookup(Identity oid)

Lookup object with Identity oid in objectTable. returns null if no matching id is found

Specified by:

lookup in interface ObjectCache

remove

public void remove(java.lang.Object obj)

removes an Object from the cache.

Specified by:

remove in interface ObjectCache

Parameters:

obj - the Object (or the Identity of the object) to be removed.

finalize

public void finalize()

Overrides:

finalize in class java.lang.Object