[Lazarus] New application type: HTTP standalone server

[michael.vancanneyt at wisa.be]

On Fri, 3 Jun 2011, ABorka wrote:

>>>>>>> On 6/2/2011 10:46, Leonardo M. Ramé wrote:
>>>>>>> >>>>>>> Michael, I added a webmodule to testhttp and got two problems.
>>>>>>> >>>>>>>
>>>>>>> >>>>>>> 1 - Could not determine HTTP module for request "". Even if I
>>>>>>> >>>>>>> call it
>>>>>>> >>>>>>> the same way as I use with fpCGI and fpEmbWeb.
>>>>>>> >>>>>>
>>>>>>> >>>>>> This error usually happens when the project main program does 
>>>>>>> not
>>>>>>> >>>>>> have
>>>>>>> >>>>>> the webmodule unit in it's uses statement.
>>>>>>> >>>>>
>>>>>>> >>>>> I managed to reproduce the error; The error is only apparent if 
>>>>>>> there
>>>>>>> >>>>> are
>>>>>>> >>>>> multiple modules registered. I committed a fix in 17647.
>>>>>>> >>>>>
>>>>>>> >>>>> This raises the question again of the FPWeb behaviour for
>>>>>>> >>>>>
>>>>>>> >>>>> http://somehost/path
>>>>>>> >>>>>
>>>>>>> >>>>> Now, 'Path' is interpreted as the name of the action for the 
>>>>>>> default
>>>>>>> >>>>> module.
>>>>>>> >>>>>
>>>>>>> >>>>> For an embedded server, this is not logical. This should be the 
>>>>>>> module
>>>>>>> >>>>> name, not the action name.
>>>>>>> >>>>>
>>>>>>> >>>>> Michael.
>>>>>>> >>>>
>>>>>>> >>>> I disagree. The vast majority of web applications do not need 
>>>>>>> multiple
>>>>>>> >>>> web
>>>>>>> >>>> modules (usually the default module is used), but they use 
>>>>>>> multiple
>>>>>>> >>>> actions.
>>>>>>> >>>> Therefore, action names should have priority over module names if 
>>>>>>> only
>>>>>>> >>>> one of
>>>>>>> >>>> them is passed.
>>>>>>> >>>
>>>>>>> >>> Hm. My experience is very different:
>>>>>>> >>> I didn't make a web application yet that had a single module.
>>>>>>> >>> All had at least 3 or 4... And they're all in production.
>>>>>>> >>>
>>>>>>> >>> Except some demo applications for FPC, they usually have 1 :-)
>>>>>>> >>>
>>>>>>> >>> Maybe we should introduce 'TWebHandler.PreferModuleName : 
>>>>>>> Boolean',
>>>>>>> >>> which
>>>>>>> >>> is
>>>>>>> >>> False by default.
>>>>>>> >>
>>>>>>> >> And you do not specify the actions in the URLs when multiple web 
>>>>>>> modules
>>>>>>> >> are in your application? I think actions are always specified when 
>>>>>>> web
>>>>>>> >> modules are in the calling URL. But it is not true the other way 
>>>>>>> around.
>>>>>>> >
>>>>>>> > Well, I never use actions. I always use the OnRequest handler of the 
>>>>>>> module
>>>>>>> > itself.
>>>>>>> >
>>>>>>> > Michael.
>>>>>>> 
>>>>>>> Heh, then we use fpweb differently (as I am sure other people prefer 
>>>>>>> doing it in many additional ways).  :)
>>>>>>> I use one single web module with dozens of actions compared to 
>>>>>>> multiple 
>>>>>>> web modules with a single request handler that sorts out things. Much 
>>>>>>> simpler and shorter calling URLs needed this way (an important thing 
>>>>>>> when encrypting the action name and request Query parameters), and for 
>>>>>>> me this way gives a nice organized source code in the web module, as 
>>>>>>> all 
>>>>>>> functions are nicely separated into action event handlers.
>>>>>>> I am sure there are many perfectly good ways - other that the two of 
>>>>>>> us 
>>>>>>> are using - to use fpweb.
>>>>>>> 
>>>>>>> In my humble opinion, if someone uses Web Actions (and they are there 
>>>>>>> and highly visible in the object inspector - not like web modules -, 
>>>>>>> as 
>>>>>>> well as Delphi-converts most probably know about them already) then 
>>>>>>> Actions have higher priority than web modules in the calling URLs. 
>>>>>>> Logically, - as a design paradigm - a web application has more actions 
>>>>>>> than web modules (not that I can really put a definition on why and 
>>>>>>> when 
>>>>>>> multiple web modules would be needed...).
>>>>>>> However, if someone is not using Web Actions at all, then this is not 
>>>>>>> true in the case they use multiple web modules.
>>>>>>> 
>>>>>>> But, since your suggestion to add a TWebHandler.PreferModuleName 
>>>>>>> (Default is False) - or similar - would not break any current 
>>>>>>> projects, 
>>>>>>> it would be an easy addition for the above cases.
>>>>>>> 
>>>>>>> I also have a question: Could you please list the function of the 
>>>>>>> multiple web modules in your web applications? I never really saw a 
>>>>>>> good 
>>>>>>> use for multiple web modules, but they were implemented more than 10 
>>>>>>> years ago in Delphi already too, so there must be a reason for that.

I separate the different functionalities in web modules. 
Look at the fpwebdata and jsonrpc parts in fcl-web.

I have one module, responsible for handling all data requests.
Another module which handles RPC requests.
A third which takes care of server management routines and producing
HTML/images.
A fourth that handles uploads/downloads of files.
etc.

Modules are rarely very long (a couple of thousand lines at most).

Usually, complete modules can be re-used in another application.
This is harder to do if you are using actions.

Also, since there are several members in a team, each person usually works on 
different modules. This keeps the chances of conflicts in SVN minimal.

Michael.