[jbosscache-dev] Let's make 3.0 backwards compatible

[Jason T. Greene]

Manik Surtani wrote:
> 
> On 19 Aug 2008, at 06:53, Bela Ban wrote:
> 
>> First of all: I don't think there's a need to make 1.x compatible with 
>> 2.x and/or 3.x. The need is there to make 2.x compatible with 3.x.
> 
> I don't know about that.  There are still a lot of people who are on AS 
> 4.x and who won't switch to AS 5.0 for a while to come.  Which means 
> they will be stuck on 1.x APIs.  See the forum link that sparked off 
> this thread

Thinking about the 4.x problem, API BC is just part of the problem. 
Behavioral differences in use by the AS clustering code and hibernate 
(i.e. AS4 clustering was not written for 3.x), as well as dependency 
differences (1.4.x uses a different jgroups).

The root of the problem here is that the AS is exposing it's internally 
used APIs, and thereby forcing them on users. If this was not the case 
(as it is on other container environments), then users could happily 
deploy JBC 3 on AS4.2, and still use EJB/HTTP clustering

The SPI that Brian is planning helps, but it requires that the user 
change the AS clustering implementation, just to change the version of 
JBC he/she is using. This could impact other components that share deps 
(JBoss Messaging).

The easiest way to fix this problem, which is done by everyone else, is 
to put all of the classes used by AS internally under a new namespace 
(package). It could also be done via a special classloader design, 
although that would be a massive change, since everyone uses the context 
loader for everything.

We just might not have a simple solution to deploying on 4.2, besides 
ripping out the clustering modules.

> We could but that would mean some sort of package renaming or class 
> renaming (e.g., o.j.c.Cache -> o.j.c.Cache3 or o.j.c.3.Cache) and 
> o.j.c.Cache remains 2.x compatible.  Either way, very ugly for anyone 
> who wants to use 3.x APIs directly.
> 
> Specifically, interfaces that have changed include:
> 
> - Cache
> - Fqn
> - EvictionConfig
> - Region/RegionManager
> - EvictionAlgorithm
> 

IMO, we can just make this stuff BC for the 3.x release.

-- 
Jason T. Greene
JBoss, a division of Red Hat