On Aug 26, 2010, at 5:06 PM, Justin Deoliveira wrote:
Hi all,
I wanted to bring a topic up for some discussion. Currently i am working on the monitoring community module that uses a top level servlet filter to control the monitoring process. Historically servlet filters have only been made active by modifying web.xml of the geoserver instance being deployed. Unfortunately in this case that does not really work since the monitoring module is an unstable community module. And even when it becomes an extension making the user manually edit the web.xml to enable it does not seem very nice.
So to remedy this I came up with servlet filter implementation that looks up other servlet filters in a spring context and delegates to them accordingly. With this it is possible to plug in servlet filters via the spring context. For those interested I have attached the class to this jira:
http://jira.codehaus.org/browse/GEOS-4114
So the question is a) is this a good idea?
yes 
and b) if so should this be constrained to trunk only?
don't see why.
One (minor) consideration would be that we might better define a separate interface from javax.servlet.Filter.
I like the class attached to the issue and agree these spring managed filters don't need the init(ServletContext) method to be called. Being spring beans all the context they might possibly need is the app context and there's a spring way of getting at it, so no need for init(ApplicationContext) neither. A cheaper alternative would be the extension point be an abstract class instead that extends Filter and has it's init(FilterContext) final (though that reminds me of xml's extension by restriction 
)
Another difference with normal servlet filters is that there's no way to declare chain order, so we need to make really explicit that filters implemented this way shall only be used when execution order doesn't matter, and that they'll be applied after all the ones declared in web.xml?
2c.-
Gabriel
Any feedback appreciated. Thanks.
-Justin
--
Justin Deoliveira
OpenGeo - http://opengeo.org
Enterprise support for open source geospatial.
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Gabriel Roldan
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