oracle.jbo.pool
Class ResourceInfo

java.lang.Object
  oracle.jbo.pool.RecentlyUsedLinkedListElement
      oracle.jbo.pool.ResourceInfo

public class ResourceInfo
extends RecentlyUsedLinkedListElement

This class tracks the objects being pooled with a reference counting mechanism. This is a general description of the states followed by their expected transitions.

Base states:

• STATE_NEW -- The resource has just been created. A resource is only in this state until the first state transition occurs.
• STATE_AVAILABLE -- The resource may be selected by useResource. The resource may also be selected for garbage collection by the pool.
• STATE_DESTROYED -- The resource has been destroyed by the pool. There may be a lag here between pool destruction and JVM finalization if the resource was referenced at the time that it is destroyed.
• STATE_INVALID -- Not used.

Extended states:

• STATE_RELEASED -- The resource is not "used". A resource is only used if a thread has invoked useResource and has not yet invoked a matching releaseResource. For useexclusive mode the ApplicationPool should not transition a resource to released state until the last referencing thread has released that resource.
• STATE_REFERENCED -- The resource is not referenced. The resource has a positive ref count. This state actually tracks with RELEASED (a released resource is always unreferenced and a referenced resource is always not released) but the state is used by a different subsystem (useexclusive). I think we could polish this by combining the two. The historical reason for the two is simply that the two states evolved from different implementations -- REFERENCED has always been a ResourcePool state while RELEASED was only promoted to a ResourcePool state recently.

After checkout the following states are expected:

1. useexclusive=true. STATE_REFERENCED
2. useexclusive=false. STATE_REFERENCED | STATE_AVAILABLE.
After checkin the following states are expected:
1. Reserved checkin (useexclusive=false). STATE_RELEASED
2. Shared checkin (useexclusive=true). STATE_AVAILABLE | STATE_RELEASED
1. useexclusive=true. n-1st referencing thread release - STATE_AVAILABLE | STATE_REFERENCED
2. useexclusive=true. nth referencing thread release - STATE_AVAILABLE | STATE_RELEASED

Field Summary

static byte	STATE_AVAILABLE
static byte	STATE_BASE_FILTER
static byte	STATE_DESTROYED
static byte	STATE_INVALID
static byte	STATE_NEW
static byte	STATE_REFERENCED
static byte	STATE_RELEASED

Constructor Summary

ResourceInfo(java.lang.Object resource)


Method Summary

Methods inherited from class oracle.jbo.pool.RecentlyUsedLinkedListElement

getLastUpdate, getLessRecentlyUsedElement, getMoreRecentlyUsedElement, getRefObject, isInList

Methods inherited from class java.lang.Object

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

Field Detail

STATE_NEW

public static final byte STATE_NEW

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Constant Field Values

STATE_AVAILABLE

public static final byte STATE_AVAILABLE

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Constant Field Values

STATE_DESTROYED

public static final byte STATE_DESTROYED

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Constant Field Values

STATE_INVALID

public static final byte STATE_INVALID

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Constant Field Values

STATE_RELEASED

public static final byte STATE_RELEASED

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Constant Field Values

STATE_REFERENCED

public static final byte STATE_REFERENCED

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Constant Field Values

STATE_BASE_FILTER

public static final byte STATE_BASE_FILTER

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Constant Field Values

Constructor Detail

ResourceInfo

public ResourceInfo(java.lang.Object resource)