Re: [xwiki-devs] [Proposal] Define XClass property types using components

On Mon, Oct 22, 2012 at 1:13 PM, Thomas Mortagne &lt;thomas.mortagne(a)xwiki.com&gt; wrote: > > On Mon, Oct 22, 2012 at 11:33 AM, Marius Dumitru Florea > &lt;mariusdumitru.florea(a)xwiki.com&gt; wrote: >> >> On Mon, Oct 22, 2012 at 12:15 PM, Thomas Mortagne >> &lt;thomas.mortagne(a)xwiki.com&gt; wrote: >>> >>> On Mon, Oct 22, 2012 at 10:36 AM, Marius Dumitru Florea >>> &lt;mariusdumitru.florea(a)xwiki.com&gt; wrote: >>>> >>>> Hi devs, >>>> >>>> Currently, the available XClass property types are hard-coded in >>>> MetaClass [1]. So in order to add a new property type you need to >>>> recompile the XWiki old core. I'd like to be able to create new >>>> property types using components so I created this branch [2] that >>>> includes the following important changes: >>>> >>>> (A) Use the value of the "classType" XML element from the XAR as a >>>> property type hint >>>> >>>> If you look at the XML export of an XClass you'll see that each >>>> property has a "classType" element whose content is the full name of >>>> the Java class used to implement that property type: >>>> >>>> <classType>com.xpn.xwiki.objects.classes.DBTreeListClass</classType> >>>> >>>> I think this is bad because: >>>> * it exposes an implementation detail >>>> * you cannot change the property type implementation without >>>> breaking >>>> backwards compatibility >>>> >>>> So I'm proposing to use the "classType" as a hint for the property >>>> type. Well, technically it will be a hint, but semantically it will >>>> specify the data type of the property value (e.g. String, Date, >>>> Number). For backwards compatibility, the existing property types >>>> will >>>> have hints that can be extracted from the value of the 'classType' >>>> (i.e. the full Java class name): >>>> >>>> String hint = >>>> StringUtils.removeEnd(StringUtils.substringAfterLast(classType, >>>> "."), "Class"); >>>> >>>> So both: >>>> >>>> <classType>com.xpn.xwiki.objects.classes.DBTreeListClass</classType> >>>> <classType>DBTreeList</classType> >>>> >>>> will point to the property type with hint "DBTreeList". Of course, >>>> when exporting an XClass with the new version of the core you'll >>>> only >>>> see the property type hint. >>>> >>>> The only issue with this approach is that XClasses exported with the >>>> new version will not work on an older version but this is acceptable >>>> IMO. >>> >>> I don't like breaking stuff too much especially when it's far from >> >> To be clear. This is not backwards compatibility. Are you sure that a >> XAR from 4.2 can be imported in XWiki 1.0 for instance? In other >> words, whenever we extended the XAR/XML format did we take care to >> keep the new XARs working on older versions of XWiki? If the answer is >> yes then I agree with your suggestions below. But for me it's enough >> to ensure that older XARs work with newer versions of XWiki, not the >> other way around. > > I don't have any breaking change in mind except that obviously a 2.0 > document is not going to be parsed properly with XWiki version that > only knows 1.0. > > Anyway the point is not if it's going to fully work with XWiki 1.0. > I don't see any reason to break anything here and it's not even like > either of my suggestions was introducing any important complexity in > your proposal. Sure. That's what I did initially. My latest code is a bit more complex exactly because I didn't wanted to use the full Java class name as hint. So it's a choice between: 'don't break anything' and 'hide technical details from the XML'. I'm more for the second option but let's see what others think.

Thanks, Marius >> Thanks, >> Marius >> >>> mandatory technically. We could either: >>> * keep theses old classType and have cleaner ones for new types. It's >>> not a big deal IMO, we are talking about oldcore API here and we will >>> have to introduce a new component API for this anyway with the new >>> model. >>> * or simply introduce a new field in the class which would fallback >>> on >>> String hint = >>> StringUtils.removeEnd(StringUtils.substringAfterLast(classType, >>> "."), "Class"); when it's not defined >>> >>>> (B) Add a PropertyClassProvider [3] role to retrieve an instance of >>>> a >>>> property class and to access its meta class >>>> >>>> Currently, in order to define a new property type you need to create >>>> two Java classes: >>>> * one extending PropertyMetaClass, to define the list of meta >>>> properties of the new property type (e.g. displayType, dateFormat, >>>> multiSelect, etc.) >>>> * one extending ProperyClass, to define setters and getters for the >>>> meta properties and maybe some custom display. This is the property >>>> type itself. >>>> >>>> So I added a PropertyClassProvider role that has two methods: one to >>>> get the meta class and one to get a new instance of the property >>>> type >>>> (e.g. when adding a property to an XClass). As a quick >>>> implementation >>>> I transformed all meta classes into implementations of this role. >>>> Finally, I modified MetaClass to lookup property class providers >>>> instead of hard-coding the property types. >>>> >>>> WDYT? >>>> >>>> Note that I've not added any CLIRR excludes and I tested my changes >>>> with the default, unchanged, class editor and it works fine. >>>> >>>> Thanks, >>>> Marius >>>> >>>> [1] >>>> >>>> https://github.com/xwiki/xwiki-platform/blob/xwiki-platform-4.2/xwiki-platf… >>>> [2] >>>> >>>> https://github.com/xwiki/xwiki-platform/compare/feature-xclass-property-com… >>>> [3] >>>> >>>> https://github.com/xwiki/xwiki-platform/commit/fb9fcc7313ccb16f38c2d17dd7ed… >>>> _______________________________________________ >>>> devs mailing list >>>> devs(a)xwiki.org >>>> http://lists.xwiki.org/mailman/listinfo/devs >>> >>> >>> >>> -- >>> Thomas Mortagne >>> _______________________________________________ >>> devs mailing list >>> devs(a)xwiki.org >>> http://lists.xwiki.org/mailman/listinfo/devs >> >> _______________________________________________ >> devs mailing list >> devs(a)xwiki.org >> http://lists.xwiki.org/mailman/listinfo/devs > > > > -- > Thomas Mortagne > _______________________________________________ > devs mailing list > devs(a)xwiki.org > http://lists.xwiki.org/mailman/listinfo/devs _______________________________________________ devs mailing list devs(a)xwiki.org http://lists.xwiki.org/mailman/listinfo/devs