Re: [POOL] Pool listeners

[David Graham]

I would make PoolListener more closely match the Java listener style.  That 
is:
1. PoolListener extends java.util.EventListener

2. The methods accept an event object that extends java.util.EventObject
(maybe call it PoolEvent).
3. The methods shouldn't throw Exception.  They should throw specific 
exception types or non at all.

I like the concept.

David




From: "Quinton McCombs" <[EMAIL PROTECTED]>
Reply-To: "Jakarta Commons Developers List" 
<[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Subject: [POOL] Pool listeners
Date: Fri, 28 Feb 2003 13:19:48 -0600

I am working on a patch to allow listeners to be added to pools that
will receive notifications on various events.  Does anyone object to
having this functionality included?
Here is the design -

I was thinking about adding support for a PoolListener interface for the
pool component.  Object which implement this interface could be added to
any ObjectPool or KeyedObjectPool.  The listener would be notified on
the following events:
- An object is borrowed from the pool
- An object is returned to the pool
- An new object is created and added to the pool
- An object is removed from the pool
addListener(PoolListener) would be defined in ObjectPool and
KeyedObjectPool.  It would be implemented in BaseObjectPool and
BaseKeyedObjectPool.  Also in the previous two Base* classes, protected
methods would be added to handle sending out the notifications to the
list of listeners.
public interface PoolListener
{
    /**
     * Executed immediatedly before an object is returned from the pool.
     *
     * @param obj The object being returned
     * @throws Exception generic exception
     */
    void onBorrow(Object obj) throws Exception;
    /**
     * Executed immediately after an object is returned to the pool.
     *
     * @param obj the object being returned
     * @throws Exception generic exception
     */
    void onReturn(Object obj) throws Exception;
    /**
     * Executed immediately after a new object is created but before it
     * is added to the pool.
     *
     * @param obj  the newly created object
     * @throws Exception generic exception
     */
    void onCreate(Object obj) throws Exception;
    /**
     * Executed when an object is removed from the pool.
     *
     * @param obj The object being removed.
     * @throws Exception generic exception
     */
    void onDestroy(Object obj) throws Exception;
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