[opencms-dev] how to creat a custom collector

[MickyW]

hi,
I'd like to create a new ressource collector but I can't find any
information on how to do this.
To be more specific, I need to know :
- which class to subclass (or an example of collector class so I could just
study existing code)
- how to make my collector available in OpenCms like the other ones (through
the property.collector of a resource)
- if it is possible to put such a class in a module and to make it available
y just installing the module (without further file config)
- where to modify the format of the param of the collector: current format
is  "[filename]|[resource type]|[count]"as I would like to add collector
specific optionnal param(or perhaps I can do this without modifying OpenCms
code ?)

what I want to do is something similar to sql queries : i want X first
essources from folder A whose property P contains a certain tag T where X,
P, T would be custom optional parameters.Would take a few seconds with a
database query and seems to be a pretty asic need for a CMS
but I don't see any other way to do this with OpenCms. Perhaps am I missing
something?
thanks in advance

mickael