A generator with sitemap parameter in C3

Question 1:
Can we have some example of this one ?

<map:generate type="some-custom">
   <map:parameter name="a" value="1"/>
   <map:parameter name="b" value="2"/>
</map:generate>

I mean, how to get sitemap parameter value from Java Generator code ?
btw. Request Parameters are obtained by the use of HttpContextHelper, is
this correct ?

Question 2:
What is the best (optimal) way to include XML content generated from
servlet/controller?

<x:include .... src="servlet:/..."/>

If the servlet is calling a REST controller there are 2 invocations
involved (one to gather data, the other one (with e.g. string-template) to
actually serialize the data). Is there any way that REST controller could
serialize the data itself ? without invoking another servlet/Page ?

Question 3:
If the generator is included in some transformer phase (via x:include)
does it still have access to original Request Parameters when invoked with:

<x:include ... src="servlet:/generate?par1=a&par2=b/>

or they are lost (original request params) and substituted by new ones
(par1, par2 from the line above) ?


Greetings,
-Greg