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.
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