[hibernate-dev] SessionEventsListener feature (HHH-8654)

[Gunnar Morling]

Yes, at least that seems to be the more common convention. I could find way
more classes named *EventListener than *EventsListener in my IDE and on
Google, and there are also examples of *EventListener types handling
several event types, e.g. javax.sql.ConnectionEventListener.

--Gunnar



2013/11/15 Steve Ebersole <steven.ebersole at gmail.com>

> Even though you have multiple event*s* being handled?
>
>
> On Thu 14 Nov 2013 06:20:09 AM CST, Sanne Grinovero wrote:
>
>> On 14 November 2013 11:36, Gunnar Morling <gunnar at hibernate.org> wrote:
>>
>>> Hi,
>>>
>>> This sounds very promising.
>>>
>>> Regarding the suggested type names, I'd personally prefer
>>> SessionEventListener
>>> (without the plural "s") and something like BaseSessionEventListener
>>> instead of EmptySessionEventsListener, as "empty" implies a specific
>>> behavior which a sub-class would not satisfy when overriding methods.
>>>
>>
>> +1
>> +1
>>
>> Sanne
>>
>>
>>> --Gunnar
>>>
>>>
>>>
>>>
>>> 2013/11/13 Steve Ebersole <steve at hibernate.org>
>>>
>>>  I wanted to highlight a new feature in 4.3 as it came about from
>>>> performance testing efforts.  Its a way to hopefully help track down
>>>> potential performance problems in applications that use Hibernate. In
>>>> this way it is similar to statistics, but it operates per-Session
>>>> (though certainly custom impls could role the metrics up to a SF level).
>>>>
>>>> It revolves around the SessionEventsListener[1] interface which
>>>> essentially defines a number of start/end pairs for the interesting
>>>> events (for example starting to prepare a JDBC statement and ending that
>>>> preparation).
>>>>
>>>> Multiple SessionEventsListener instances can be associated with the
>>>> Session simultaneously.  You can add them programatically to a Session
>>>> using Session#addEventsListeners(SessionEventsListener...) method.
>>>>  They
>>>> can also be added to the Session up-front via the
>>>> SessionFactory#withOptions API for building Sessions.
>>>>
>>>> Additionally there are 2 settings that allow SessionEventsListener impls
>>>> to be applied to all Sessions created:
>>>>
>>>> * 'hibernate.session.events.auto' allows you to name any arbitrary
>>>> SessionEventsListener class to apply to all Sessions.
>>>> * 'hibernate.session.events.log' refers to a particular built-in
>>>> implementation of SessionEventsListener that applies some timings across
>>>> the start/end pairs
>>>> (org.hibernate.engine.internal.LoggingSessionEventsListener).  In fact
>>>> this listener is added by default if (a) stats are enabled and (b) the
>>>> log level (currently INFO) of LoggingSessionEventsListener is enabled.
>>>> Below[2] is some sample output of LoggingSessionEventsListener.
>>>>
>>>> There is also a org.hibernate.EmptySessionEventsListener (no-op) class
>>>> to help develop custom ones.
>>>>
>>>> Anyway, as much as anything I wanted to point it out so people can try
>>>> it out and to get feedback.  I think the API covers most of the
>>>> interesting events.  If you feel there are any missing, lets discuss
>>>> here or on a Jira issue.
>>>>
>>>>
>>>> [1] https://gist.github.com/sebersole/7438250
>>>>
>>>> [2]
>>>> 14:40:20,017  INFO LoggingSessionEventsListener:275 - Session Metrics {
>>>>       9762 nanoseconds spent acquiring 1 JDBC connections;
>>>>       0 nanoseconds spent releasing 0 JDBC connections;
>>>>       1020726 nanoseconds spent preparing 4 JDBC statements;
>>>>       1442351 nanoseconds spent executing 4 JDBC statements;
>>>>       0 nanoseconds spent executing 0 JDBC batches;
>>>>       0 nanoseconds spent executing 0 L2C puts;
>>>>       0 nanoseconds spent executing 0 L2C hits;
>>>>       0 nanoseconds spent executing 0 L2C misses;
>>>>       2766689 nanoseconds spent executing 1 flushes (flushing a total of
>>>> 3 entities and 1 collections);
>>>>       1096552384585007 nanoseconds spent executing 2 partial-flushes
>>>> (flushing a total of 3 entities and 3 collections)
>>>> }
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