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From pkriens <Peter.Kri...@aQute.biz>
Subject Re: Osgifing Tomcat
Date Mon, 28 Apr 2008 10:52:09 GMT

> To me, a webapp adds "entries" (aka Servlet) to menus (aka url patterns) 
> from a static file inside the war (web.xml). If it was not possible in 4 
> years to solve this problem in Eclipse, how will it be possible for
> Tomcat?
More and more code is supporting the dynamic life cycle model because it is 
not that hard and the Eclipse people like it. However, you should realize
that 
there is a very diverse community out there. Only recently is OSGi on their 
radar.

Providing a mechanism to get servlets registered from the web.xml are
available.
The OPS 4J guys are providing tools and bundles:
http://wiki.ops4j.org/confluence/display/ops4j/Pax+Web+Extender. It is
actually not
that hard. However, if a web app creates resources, it also needs cleanup.
Much of the
cleanup can be done on the server side because you can get an event when a
bundle stops. 
I.e. in the OSGi Http Service, it is required to automatically unregister a
servlet when a 
bundle is stopped. In some cases, the cleanup must be performed by the web
app itself. 
In those case, the web app must implement some code that is called when the
bundle
is stopped.

This may all sound scary and complex, but it is surprisingly simple when you
try it 
out because it feels very natural in an OSGi environment. Programming models
like Spring DM, iPOJO, DS, etc. can further help to support this model while
not showing up in any Java code.

Kind regards,

   Peter Kriens
 



Damien Bonvillain wrote:
> 
> pkriens wrote:
>>> Just my 2c: Eclipse, OSGified since 3.2, still doesn't fully support 
>>> updates without a JVM restart; and they have full control about the 
>>> whole aspects.
>> Unfortunately there are tens of thousands of plugin writers out there
>> that
>> are not aware of the dynamics. Eclipse migrated to OSGi 4 years ago and
>> did
>> some incredible open heart surgery on their runtime engine to support
>> OSGi.
>> It was quite impressive how they replace their engine with an OSGi based
>> version while existing plugins kept working. However, none of the
>> existing
>> code was ready for the consequences of dynamics. Plugins could add
>> entries
>> to menu's but this information came from a static file in the plugin, so
>> there was no facility to remove this information. 
> 
> To me, a webapp adds "entries" (aka Servlet) to menus (aka url patterns) 
> from a static file inside the war (web.xml). If it was not possible in 4 
> years to solve this problem in Eclipse, how will it be possible for
> Tomcat?
> 
> Damien
> 
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> 

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