[xwiki-devs] VelocityFactory API change (was Re: xwiki-velocity refactoring)

Sergiu Dumitriu sergiu at xwiki.com
Thu Mar 3 00:51:26 UTC 2011

On 03/02/2011 06:44 PM, Vincent Massol wrote:
> I forgot to menton the alternative which is to create a WebAppVelocityFactory component impl (hint = "webapp"), in the same manner that I have already created WebAppVelocityConfiguration and WebAppVelocityEngine.
> I think my preference foes to the API modification now.

I don't like either one.

Adding the hint parameter to the API is nice if there ever will be a 
need to have different types of engines at runtime. Do we have this need 
at the moment? I don't think so, so IMO it's better to keep the API as 
simple as possible while still serving our needs.

Implementing WebAppVelocityFactory somehow beats the definition of a 
factory, at least in my view. A factory usually is a single class that 
knows how to create objects of different types. Normally the preferred 
approach is indeed to add a "hint" parameter, but as I said we don't 
really need it at the moment.

What if we just change the implementation of the factory so that the 
default hint is taken from a configuration? What we'll need to do is to 
provide a different configuration for use inside XWiki.

> Thanks
> -Vincent
> On Mar 2, 2011, at 4:49 PM, Vincent Massol wrote:
>> ok I have no added the following 2 new component impls:
>> * WebAppVelocityConfiguration
>> * WebAppVelocityEngine
>> However it's not enough since DefaultVelocityEngine.createVelocityEngine() does a component lookup on VelocityEngine and we need a way for it to look up with a passed hint.
>> I'm proposing to modify the current VelocityFactory API from:
>>     VelocityEngine createVelocityEngine(String key, Properties properties) throws XWikiVelocityException;
>> to:
>>     VelocityEngine createVelocityEngine(String key, Properties properties, String engineType) throws XWikiVelocityException;
>> where engineType is the hint corresponding to the engine to look up.
>> Then DefaultVelocityManager can call VelocityFactory, passing the "webapp" hint to createVelocityEngine.
>> WDYT?
>> Thanks
>> -Vincent
>> On Mar 2, 2011, at 1:56 PM, Vincent Massol wrote:
>>> Just a heads up of what I'm working on right now: cleaning up xwiki-velocity dependencies.
>>> I'm going to split it into several submodules:
>>> * xwiki-velocity-management (or xwiki-velocity-jmx)
>>> * xwiki-velocity-default
>>> * xwiki-velocity-webapp (implementation of VelocityEngine and VelocityConfiguration with hint = "webapp",  this is to use use velocity with the WebappResourceLoader loading templates from the webapp's root dir)
>>> -Vincent
Sergiu Dumitriu

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