Name: rmT116609 Date: 01/08/2002
DESCRIPTION OF THE PROBLEM :
Object pooling is a technique to improve performance by reusing objects rather than creating new ones. To pool
objects, it is necessary to determine when there are no remaining references to the object, then place this object
on a queue. There is currently no support in the JVM or Java APIs for detecting when an object has no remaining
references. While Object.finalize() is eventually called when the object has no references and can be used to
resurrect the object, but this technique will only work once because finalized() is guaranteed to only be called only
once. The subclasses of java.lang.ref.Reference are likewise no help because by the time a reference is enqueued, its
referant no longer available for resurrection.
Thus, it falls to the developer to determine when an object is poolable. Effectively, the developer becomes responsible
for memory management, with all the dangers that entails (and that Java generally avoids with automatic garbage collection).
Create two new types of java.lang.Reference that can be used to notify the developer when an object is poolable:
java.lang.ref.FinalReference would be enqueued when there are no other strong references to the referant. However,
unlike all other subclasses of java.lang.ref.Reference, the object would still be available for resurrection using
Reference.get() when the reference is enqueued.
java.lang.ref.SoftFinalReference would behave like FinalReference except that refereants will not be enqueued
if there is a low memory condition (following the same algorithm as java.lang.ref.SoftReference). This would enable
One additionial advantage of FinalReference is that it would enable examination of an object (e.g. for logging
purposes) before that object is garbage collected.
STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Try to do pooling manually with a complex project.
2. Get memory management problems :-)
CUSTOMER WORKAROUND :
Perform pooling manually and use sophisticated tools and lots of time to track down errors.
(Review ID: 138035)