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.<p/> 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_UNAVAILABLE -- The resource may not be select by useResource. The resource may also not be accessed 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.
• n.b. Not sure why both AVAILABLE and UNAVAILABLE states are being carried. <p/> 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.
  <p/> After checkout the following states are expected:
  1. useexclusive=true. STATE_REFERENCED | STATE_UNAVAILABLE.
  2. useexclusive=false. STATE_REFERENCED | STATE_AVAILABLE.
  After checkin the following states are expected:
  1. Reserved checkin (useexclusive=false). STATE_UNAVAILABLE | STATE_RELEASED
  2. Shared checkin (useexclusive=true). STATE_AVAILABLE | STATE_RELEASED
  3. 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
  static byte	STATE_UNAVAILABLE

  Constructor Summary

  ResourceInfo(java.lang.Object resource)
  

  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_UNAVAILABLE

  public static final byte STATE_UNAVAILABLE
  

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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)