Re: Next Layer for web apps on top of CPPSERV

[Boris Itkis <boris_itkis@yahoo.com>]

Speaking of a template engine, links bellow represent
tree basic approaches we are to chose from, each has
its own straights and weaknesses:

http://teng.sourceforge.net/  -- byte-code based
template engine;
http://codesynthesis.com/projects/xsd/ -- XML Scheme
to C++ classes, a lot of deps;
http://tazthecat.net/~isaac/libtpt/ -- self-contained
template language.

IMHO, the third approach suites our purposes the best.

To be continue...

--Boris


--- "Ilya A. Volynets-Evenbakh"
<ilya@total-knowledge.com> wrote:

> To summarize our recent discussion about web
> framework and also mix in
> some of my thoughts that came after.
> 
> What we'd like to be able to do is ability to make
> calls along the lines of
> 
>
http://myserver/MyApp/Object.function?arg1=xx&arg2=yy
> 
> (alternatively arguments could be passed as POST
> data).
> 
> This framework will also need to support
> serialization (for persistent
> storage in database, and perhaps for argument
> passing.
> 
> It will also need to be able to validate parameters
> to function calls
> at least minimally both at compile time and at run
> time.
> 
> Another part will be template language that can be
> integrated with
> CPPSERV. It will be compiled language - most likely
> translating
> to C++ first. Ability to bind functions and forms in
> template
> in such a way that will allow compile-time
> verification of correlation
> between templates, generated HTML, and function
> parameters
> would be nice to have.
> 
> Whole application would therefore contain following
> parts:
> 
> 1. The servlet (most likely just a class derived
> from
>     framework base servlet, and setting up few
> properties
>     like app name)
> 2. Description of exported classes / methods / their
> parameters
> 3. Description of mappings between serializable
> objects
>     and storage structure elements.
> 4. Set of templates for UI.
> 
> Export description can be used to generate wrapper
> classes
> that will be used to marshal/demarshal data and
> provide
> verification function.
> 
> Now, templates are somewhat more complex issue.
> Main question is how to exchange data between
> template
> and calling code.
> One option is something like Velocity engine -
> templates
> caller explicitly binds all variables.
> Another idea is that each template ends up being a
> function
> and all external variables end up being function
> parameters.
> This gives us compile-time validation of coherency
> between
> data template expects and data template user
> supplies.
> 
> Another important feature of template processor
> would be
> verifying that forms in template provide all
> elements needed
> by functions being called.
> 
> I think I'll end here for now.
> 
> 
> Ilya A. Volynets-Evenbakh wrote:
> 
> >So, here is the idea for next layer to build on top
> of CPPSERV.
> >
> >What I want to have, is an application framework,
> which allows me to
> >write my objects whith their functions and _not_ to
> worry about deciding
> >which function to call wen.
> >
> >Let's take a standard example: on-line retail
> store.
> >I could define following classes: Catalogue,
> Category, Item, Order,
> >OrderItem, etc.
> >They would all have their respecitve member
> functions to do whatever
> >modifications
> >to object state they need.
> >
> >Now, as it is, I would probably write one or
> perhaps few servlets, that
> >would take
> >some sort of "action" parameter, as well as other
> data, and based on
> >that decide
> >which function to invoke for given request. I would
> need to organise and
> >track precisely
> >which objects call which functions, how they
> interact, etc.
> >
> >i.e. Catalogue object could generate calls to
> Category and Item objects,
> >along the lines of:
> >
> ><A
>
HREF="StoreServlet?oid=xzzy11102&action=display>Fruits</A>
> ><A
>
HREF="StoreServlet?oid=xzzy11103&action=display>Vegetables</A>
> >
> ><A
>
HREF="StoreServlet?oid=foo1231&action=addToOrder>Apple</A>
> >
> >Now, if I ever change data that some function
> needs, i'll need to go through
> >all code, and make sure references to that function
> have all nessesary data.
> >Of course, the only way to find out if something is
> missing is through
> >exhaustive
> >testing. This is only one of maintainance problems
> - I think we could
> >easily come
> >up with many other scenarios.
> >
> >The framework I have in mind should take care of
> this at compile-time.
> >i.e. it should allow to generate calls to other
> objects and do parameter
> >checking,
> >either through macros, or, better through class
> templates. It should
> >also take
> >care of dispatching calls, and basic verification
> of argument validity
> >at run-time.
> >
> >Another aspect of any large web application is
> object persistance and object
> >caching. I am not sure at this point if these
> functions should be part
> >of same
> >framework, or should be separated, and be used in
> conjunction with each
> >other.
> >
> >  
> >
> 
> -- 
> Ilya A. Volynets-Evenbakh
> Total Knowledge. CTO
> http://www.total-knowledge.com
> 
>