Re: [xwiki-devs] [Proposal] How to bridge the gap between Java APIs and Velocity code

Hi, In the new component-based architecture we are creating lots of specific apis that we need to make available to velocity. For example the rendering module should make available it's XDO object so that users can access any part of a document. However there are some impedance mismatch. For example in XDOM the method to find all blocks of a given type today is: XDOM.getChildrenByType(SectionBlock.class). This cannot be called from velocity since SectionBlock.class will not work. There are lots of other similar examples. One solution would be to modify the API to be for example: XDOM.getChildrenByType(String blockName) but this is ugly and type-unsafe. So I was thinking about a different approach. What about intercepting method calls in our velocity module and instead of calling the method right away have some transformation to it. The idea would be for modules to register method handlers to our velocity runtime so that it can do the conversion. For example when you'd call $xdom.getChildrenByType("section") it would call the XDOMVelocityMethodHandler.convert(...) method and transform "section" into SectionBlock.class and call the API method. Thus the idea would be that modules that want to make their APIs more velocity friendly would just create components implementing some VelocityMethodHandler interface and automatically these would be used by our velocity runtime. The only downside I can think of is javadoc or rather how users will know the method signature to use from velocity but I think we can find solutions for this. One solution for example is to use annotations on methods that need to have a velocity method hander. We'll need that anyway I think. Something like: @velocityMethodHandler("rendering"') XDOM.getChildrenByType(...) (where "rendering" is the component role-hint) WDYT?

Sergiu, since you're the one to have manipulated this part of Velocity, is this possible? (I think it is using uberspectors). Thanks -Vincent PS: Since we don't want to make our code special for Velocity we should check how we would do it for other templating engine like FreeMarker for example. _______________________________________________ devs mailing list devs(a)xwiki.org http://lists.xwiki.org/mailman/listinfo/devs