[Qgis-developer] QGIS Server Python Plugins API

[G. Allegri]

Hi Alessandro,
the concept is clear but I probably I was reading the worng repo:
serverplugins-iface, which is the latest you authored.
In this repo it seems that, in case a SERVICE different from the standards
ones is called, an exception is raised [1], while in serverplugins repo the
workflow is quite different, because the switch looks for plugin available
to process the request.

However, what you're saying is that a plugin can completely change the
incoming request and the outgoin request (I understand the middleware
concept very well being a Django dev) and so:

 - have the opportunity to server a non-standard service
 - have the opportunity to do not let the request reach the QGIS Servers'
request handlers.

I will have a look to the filter examples later.
Thanks for this work Alessandro ;)
giovanni

[1]
https://github.com/elpaso/QGIS/blob/serverplugins-iface/src/mapserver/qgis_map_serv.cpp#L423

2014-10-24 8:31 GMT+02:00 Alessandro Pasotti <apasotti at gmail.com>:

> 2014-10-23 20:20 GMT+02:00 G. Allegri <giohappy at gmail.com>:
> > Hi Alessandro,
> > I've read the latest version of the QEP and had a look to your repo.
> > If I'm not wrong the current implementation doesn't provide custom
> services
> > as in the initial proof of concept, but gives the opportunity to define
> > "middlewares" before and after the requests have been processed by the
> > standard OGC servces offered by QGIS Server. Is it right?
> >
> > giovanni
> >
>
> Hi Giovanni,
>
> Thank you for your interest in my work!
>
> You are partially right: the new implementation we agreed upon in
> Hessen is loosely based on the Django concept of middlewares, with the
> addition of the possibility to add new hooks (callbacks) in the
> future.
>
> This implementation also allows for an easy implementation of custom
> services though.
>
> In fact, this concept proved to be extremely flexible and unobtrusive
> at the same time: a plugin can define one or more "filters" [1] with
> an optional priority, the filters have access to server interface [2]
> that in turn can manipulate the request handler [3].
> By manipulating the requet handler, a plugin can intercept and alter
> the input (typically the query string) **before** entering the main
> C++ switch for core services and/or can intercept and alter the output
> **after** the main C++ switch. The output typically is one of: none
> (in case the service did not match), an exception, an image or a
> XML/HTML document.
>
> I have developed a test plugin [4] which implements the following filters:
>
> * an HTML remote python console, also implements HTTP BASIC
> Authentication to give an example of HTTP header manipulation
> * do nothing but logging the result of QUERY STRING manipulation
> tests</li>\n"
> * say HelloServer! and write some lines in the logs
> * WaterMarkFilter: adds a watermark image on top of all WMS GetImage
> requests
> * raise and exception, catched in main loop
>
> Have a look to the filters for the implementation details.
>
> For anyone interested in testing, the implementation is in my
> "serverpython" branch:
>
> https://github.com/elpaso/QGIS/tree/serverpython
>
> PLEASE NOTE THAT in a previous email I gave the address of a wrong
> branch, that one above is the right one.:
>
> [1] http://www.itopen.it/qgis/serverplugins/api/classQgsServerFilter.html
> [2]
> http://www.itopen.it/qgis/serverplugins/api/classQgsServerInterface.html
> [3]
> http://www.itopen.it/qgis/serverplugins/api/classQgsRequestHandler.html
> [4] https://github.com/elpaso/qgis-helloserver/tree/master/filters
>
> --
> Alessandro Pasotti
> w3:   www.itopen.it
>



-- 
Giovanni Allegri
http://about.me/giovanniallegri
Twitter: https://twitter.com/_giohappy_
blog: http://blog.spaziogis.it
GEO+ geomatica in Italia http://bit.ly/GEOplus
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