Hi, As described in the JAX-RS Whiteboard spec <https://osgi.org/specification/osgi.cmpn/7.0.0/service.jaxrs.html#d0e133685> JAX-RS extension instances are required to be singletons (I’m talking about the objects, not the services) by the JAX-RS specification itself. Therefore within an application you will only ever see one instance of a whiteboard extension service.
The reason that you should make extension services prototype is therefore not related to per-request handling, but instead because of what happens when the same extension service is applied to *multiple applications*. In this scenario you will have multiple applications with different configuration and different context objects. If your extension service is injected with these objects by the JAX-RS runtime (for example being injected with the Application using @Context) then which application is that for? In the general case you have no idea whether the context object you have been injected with relates to the current request or not. If your extension service is singleton or bundle scoped then the JAX-RS whiteboard can only get one instance. It therefore has to use this same instance for all of the whiteboard applications and you run into the potential “multiple injections” trap. This is obviously fine if you don’t have any injection sites, or if all your injection sites are method parameters, but it is a risky thing to do as someone may add an injection site later without realising that they’ve broken things. This will probably also make it through testing as you’ll typically only have one application at a time when testing! If your extension service is prototype scope then the JAX-RS Whiteboard is able to get a different instance to use in each whiteboard application. At this point you no longer need to worry about multiple injections because the injections happen on different instances. I hope this answers your question, and helps to further explain why prototype scope is a good thing for filters! Best Regards, Tim > On 29 Jan 2019, at 15:18, Raymond Auge via osgi-dev <osgi-dev@mail.osgi.org> > wrote: > > I'm going to assume you are talking about: > > HttpService[1] or Http Whiteboard[2] w.r.t. the reference to Servlet > AND > JAX-RS Whiteboard[3] w.r.t. the reference to ContainerRequestFilter > > These 2(3) features are separate concerns and the ContainerRequestFilter of > the JAX-RS whiteboard spec doesn't apply to the Servlets of the Http > Whiteboard. You probably just want a regular old servlet Filter[4] > > Now it's possible that you are talking about some other runtime that packs > all these things together. If so, you probably want to ask the implementors > about this. > > Hope that helps clear things up, > - Ray > > [1] https://osgi.org/specification/osgi.cmpn/7.0.0/service.http.html > <https://osgi.org/specification/osgi.cmpn/7.0.0/service.http.html> > [2] > https://osgi.org/specification/osgi.cmpn/7.0.0/service.http.whiteboard.html > <https://osgi.org/specification/osgi.cmpn/7.0.0/service.http.whiteboard.html> > [3] https://osgi.org/specification/osgi.cmpn/7.0.0/service.jaxrs.html > <https://osgi.org/specification/osgi.cmpn/7.0.0/service.jaxrs.html> > [4] > https://osgi.org/specification/osgi.cmpn/7.0.0/service.http.whiteboard.html#d0e121055 > > <https://osgi.org/specification/osgi.cmpn/7.0.0/service.http.whiteboard.html#d0e121055> > > On Tue, Jan 29, 2019 at 9:59 AM Nhut Thai Le via osgi-dev > <osgi-dev@mail.osgi.org <mailto:osgi-dev@mail.osgi.org>> wrote: > Hello, > > I have a component implementing ContainerRequestFilter to intercept REST > calls and another component implements servlet.Filter. Both have PROTOTYPE > scope, my understanding is that these filter are instantiated and activated > for each web request but yesterday when i put some breakpoints in the > @activate method, i did not see them get called when a web request arrives. > Did I miss something? If they are not init/activate per request why are they > recomeded to be prototype? > > Thai Le > _______________________________________________ > OSGi Developer Mail List > osgi-dev@mail.osgi.org <mailto:osgi-dev@mail.osgi.org> > https://mail.osgi.org/mailman/listinfo/osgi-dev > <https://mail.osgi.org/mailman/listinfo/osgi-dev> > > -- > Raymond Augé <http://www.liferay.com/web/raymond.auge/profile> (@rotty3000) > Senior Software Architect Liferay, Inc. <http://www.liferay.com/> (@Liferay) > Board Member & EEG Co-Chair, OSGi Alliance <http://osgi.org/> (@OSGiAlliance) > _______________________________________________ > OSGi Developer Mail List > osgi-dev@mail.osgi.org > https://mail.osgi.org/mailman/listinfo/osgi-dev
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