The initial issue that kicked off this thread was that, a pure JAXRS WABs fail to bootstrap karaf, where as they work as documented when deployed into the OSGi side of Glassfish.
Glassfish may be a JakartaEE platform, but essentiality it is an OSGI framework running on Felix. Therefore, felix should also support the concept of dropping annotated applications into the framework that will be picked up and initialised by the relevant extender. This process is complicated by the fact that JAXRS services are web applications that are bootstrapped by a method described in the Servlet 3 specification. This is achieved by the appropriate technology (i.e. CXF or Jersey) providing a ServletContainerInitializer that allows the service to examine application and decided if further action is required. As discussed previously the ServletContainerInitializer's are discovered through the use of the Java Util ServiceLoader service. This means that the META-INF/services file needs to be visible and creatable by the application's class loader. Or via some other means, e.g. servlet, jsp and jsf implementations are supported by the pax-web-extender specifically wiring in the appropriate class loaders during the web context initialisation process. As such I've been trying to understand how Glassfish achieved something similar in a felix container, without the need for the application to specify either the Jersey implementation or the auxiliary library that contained the SCI. It turns out that GF is using a couple of tricks to construct a common classloader at runtime which contains dependencies on all bundles that offer services through the ServiceLoader framework. This is then used as the parent classloader when bootstrapping web and other types of services, thus decoupling the web framework implementation from the applications that use it. Personally I like this approach as it allows our framework engineer to maintain the platforms separately from application developers who only need be concerned with the business logic. Thus if we want to upgrade or change the implementation of a particular technology (e.g. JAXRS, Spring, JPA, XML/JSON Binding, etc…) then we can without the need to rebuild all of the applications that use it. As a demo I have extended the ServletContainerInitializerScanner in the pax-web-api to track bundles that provide the SCI via the service loader file. These are then returned to the JettyServerWrapper when it is creating the HttpServiceContext. The result is that JAXRS, WebSocket and Spring MVC applications are all correctly initialised without the need to hard code a specific implementation into the business logic bundles. I realise that bootstrapping services like this does not conform to the class loading concepts of the OSGI specification, however it does make Karaf more flexible when used as a service platform. As such, I believe that we should consider adding the option of a SCI Bundle Extender to the pax web offering. Any thoughts on such a solution? Regards Paul Get TypeApp for Android On 6 Nov 2020, 13:48, at 13:48, Grzegorz Grzybek <[email protected]> wrote: >Hello! > >pt., 6 lis 2020 o 14:44 'paul stanley' via OPS4J ><[email protected]> >napisał(a): > >> Thanks Grzegorz, >> >> I'll have a more detailed look at this when I get back next week. >> > >Sure! Looking forward to your findings ;) > >regards >Grzegorz Grzybek > > >> >> Regards >> Paul >> On 2 Nov 2020, at 06:22, Grzegorz Grzybek <[email protected]> >wrote: >>> >>> Hello >>> >>> niedz., 1 lis 2020 o 18:56 'paul stanley' via OPS4J < >>> [email protected]> napisał(a): >>> >>>> Hi Grzegorz, >>>> >>>> Sorry about the delay in getting back to you. >>>> >>>> I realise your concerns about sci's from different webapps >interfering >>>> with each other. However the SCI mechanism appears to be the way >that the >>>> other web technologies, such as JAXRS and SpringMVC have a chance >to detect >>>> and influence the creation of the servlet. >>>> >>> >>> JaxRS and SpringMVC were designed to work in JavaEE runtime (or just >flat >>> classpath for non servlet applications) which has well defined >hierarchical >>> ClassLoader model, so scanning for SCIs is easy - just start with >current >>> ClassLoader (assigned to the WAR for example) and walk through >parents. >>> >>> OSGi has also (very) well defined ClassLoader model - but it's not >>> hierarchical, it's _network_ bidirectional graph of ClassLoaders... >>> >>> >>>> >>>> Given that ServiceLoader architecture is being used, is it >unreasonable >>>> that all possible instances for the SCI get asked to look at the >bundle and >>>> initialize the context is appropriate? >>>> >>> >>> Hmm, I'm not sure I understand... SCI in onStartup() gets an >instance of >>> ServletContext and array of classes - it should not be bundle >aware... >>> >>> >>>> >>>> If not, then we need another way to extend the WebExtender with >other >>>> web frameworks, allowing them to get involved with servlet >creation. Which >>>> does not include altering the webapp in some OSGI specific way. >>>> >>> >>> I'm not sure we can extend the WebExtender (quite low level >framework) >>> with some web framework (SpringMVC, JaxRS, Wicket, Tapestry, name it >- all >>> more high level).... >>> >>> But fear not - the best way to detect proper SCIs (IMO) is simply to >use >>> WAB archives, so all jars from Bundle-ClassPath manifest header >(which by >>> default means all jars from /WEB-INF/lib of the bundle) are scanned >for >>> SCIs and web-fragment.xmls. >>> >>> regards >>> Grzegorz Grzybek >>> >>> >>>> >>>> Cheers >>>> Paul >>>> On 30 Oct 2020, at 08:46, Grzegorz Grzybek < [email protected]> >>>> wrote: >>>>> >>>>> Hello >>>>> >>>>> czw., 29 paź 2020 o 19:50 Matt Pavlovich < [email protected]> >napisał(a): >>>>> >>>>>> Paul-- >>>>>> >>>>>> You might checkout a BundleTracker. A BundleTracker is ensured >to get >>>>>> a callback for every bundle, regardless as to when your bundle >started. >>>>>> With a BundleListener, there is a race condition that you may not >be >>>>>> activated before some bundles that you care about. >>>>>> >>>>> >>>>> It's not about bundle tracker or listener. Whiteboard >implementation >>>>> uses such tracker to ensure that when a bundle is gone, all >associated >>>>> contexts and web elements should be deregistered. >>>>> It's more about which bundles should be scanned for >>>>> ServletContainerInitializers. imagine you install two "sets" of >bundles >>>>> (e.g., Karaf features) - you don't want SCIs from one feature (web >>>>> application) to be used in another feature/web application... >>>>> >>>>> regards >>>>> Grzegorz Grzybek >>>>> >>>>> >>>>>> >>>>>> ref: >>>>>> >https://docs.osgi.org/specification/osgi.core/7.0.0/util.tracker.html#d0e52020 >>>>>> >>>>>> -Matt >>>>>> >>>>>> On Thursday, October 29, 2020 at 1:17:19 PM UTC-5 >>>>>> [email protected] wrote: >>>>>> >>>>>>> >>>>>>> Thanks Grzegorz. I know what you mean about doing my "normal >job", I >>>>>>> also have be careful as to what can be shared to the community. >>>>>>> >>>>>>> I realise that the ServiceLoader is a bit of a problem and I've >>>>>>> already had to alter other standard services to be bundle-aware. > Which is >>>>>>> why I think implementing a Bundle Listener could be a better >approach for >>>>>>> the SCI's. >>>>>>> >>>>>>> I'm out of the office for a couple of weeks so I'm going to look >>>>>>> prototyping a solution when I get back. >>>>>>> >>>>>>> Cheers >>>>>>> Paul >>>>>>> On 29 Oct 2020, at 13:28, Grzegorz Grzybek < [email protected]> >>>>>>> wrote: >>>>>>> >>>>>>>> Hello >>>>>>>> >>>>>>>> You're generally right. I'm working on Pax Web 8 improvements >>>>>>>> (actual, full implementation of OSGi CMPN R6+ Whiteboard >specification + >>>>>>>> HttpService specification + Web Applications Specification) and >I tackled >>>>>>>> the problem of ServletContainerInitializers. >>>>>>>> >>>>>>>> The problem is that OSGi CMPN spec doesn't mention SCIs at all, >only >>>>>>>> Web Applications Specification generally assumes that "web >bundle" should >>>>>>>> be processed ("extended") by the implementation which involves >web.xml >>>>>>>> parsing + fragments parsing + (possibly) "classpath scanning". >See for >>>>>>>> example: >>>>>>>> >>>>>>>> A WAB can optionally contain a web.xml resource to specify >>>>>>>>> additional configuration. This web.xml must be found with the >Bundle >>>>>>>>> *findEntries* method at the path WEB-INF/web.xml. The >findEntries >>>>>>>>> method includes fragments, allowing the web.xml to be provided >by a >>>>>>>>> fragment. >>>>>>>>> >>>>>>>> >>>>>>>> So here there's nothing about "scanning other bundles" not >referred >>>>>>>> through "fragment" relationship. >>>>>>>> >>>>>>>> Also: >>>>>>>> >>>>>>>> Unlike a WAR, a WAB is not constrained to package classes and >code >>>>>>>>> resources in the WEB-INF/classes directory or dependent JARs >in >>>>>>>>> WEB-INF/lib/ only. These entries can be packaged in any way >that's valid >>>>>>>>> for an OSGi bundle as long as such directories and JARs are >part of bundle >>>>>>>>> class path as set with the Bundle-ClassPath header and any >attached >>>>>>>>> fragments. JARs that are specified in the Bundle-ClassPath >header are >>>>>>>>> treated like JARs in the WEB-INF/lib/ directory of the Servlet >>>>>>>>> specification. Similarly, any directory that is part of the >>>>>>>>> Bundle-ClassPath header is treated like WEB-INF/classes >directory of the >>>>>>>>> Servlet specification. >>>>>>>>> >>>>>>>> >>>>>>>> So again - you can "bring" additional libraries to your "bundle >>>>>>>> classpath" by referring them in "Bundle-ClassPath" header. No >scanning of >>>>>>>> everything (that's for example tracked by BundleListener). >>>>>>>> >>>>>>>> And about java.util.ServiceLoader (which should in theory be a >>>>>>>> suggestion to how ServletContainerInitializer "services" are >found), >>>>>>>> "java.util.ServiceLoader#load(java.lang.Class<S>, >java.lang.ClassLoader)" >>>>>>>> method simply uses the passed classLoader and the other >"load()" version >>>>>>>> uses TCCL. Neither of these methods scan ALL classloaders (all >bundles in >>>>>>>> OSGi). >>>>>>>> >>>>>>>> In Pax Web 8 I'm definitely going to solve this problem - for >now, a >>>>>>>> bundle that registered "a context" >>>>>>>> (org.osgi.service.http.context.ServletContextHelper) is an >"entry point" to >>>>>>>> classLoader "mesh" where all are checked for SCIs. >>>>>>>> >>>>>>>> My Pax Web 8 refactoring is taking its shape at >>>>>>>> >https://github.com/ops4j/org.ops4j.pax.web/tree/master-improvements >>>>>>>> branch, but I have to do my normal job a bit ;) So please be >patient. >>>>>>>> >>>>>>>> regards >>>>>>>> Grzegorz Grzybek >>>>>>>> >>>>>>>> >>>>>>>> czw., 29 paź 2020 o 14:13 'paul stanley' via OPS4J < >>>>>>>> [email protected]> napisał(a): >>>>>>>> >>>>>>>>> Hello. >>>>>>>>> >>>>>>>>> I'm tracing this through to try and understand why Jersey >Servlet >>>>>>>>> Initializer is not invoked for a pure Jaxrs applications >running in Karaf >>>>>>>>> 4.3.0. >>>>>>>>> >>>>>>>>> It appears the way that the ServletContainerInitializerScanner >in >>>>>>>>> the pax-web-api has a fundamental design flaw when it >searches bundles for >>>>>>>>> instances of the /META-INF/services/ >ServletContainerInitializerScanner >>>>>>>>> file. Namely that it only searches dependent bundles of the >one that is >>>>>>>>> being initialised. As the implementation of any service is >meant to be >>>>>>>>> hidden by the API, it means that you will never be able to >initialise any >>>>>>>>> web servlet. As such the pax-jetty-web adds the bodge of >wiring-in itself >>>>>>>>> to all web-context so its contextInitializer code can be >discovered, but no >>>>>>>>> other implementations. >>>>>>>>> >>>>>>>>> Rather than performing a bundle scan each time, surely jetty >should >>>>>>>>> be implementing the bundle listener pattern and have the set >of servlet >>>>>>>>> initializers that are available in the platform? Or am I >missing something? >>>>>>>>> >>>>>>>>> Cheers, >>>>>>>>> >>>>>>>>> Paul >>>>>>>>> >>>>>>>>> -- >>>>>>>>> -- >>>>>>>>> ------------------ >>>>>>>>> OPS4J - http://www.ops4j.org - [email protected] >>>>>>>>> >>>>>>>>> --- >>>>>>>>> You received this message because you are subscribed to the >Google >>>>>>>>> Groups "OPS4J" group. >>>>>>>>> To unsubscribe from this group and stop receiving emails from >it, >>>>>>>>> send an email to [email protected]. >>>>>>>>> To view this discussion on the web visit >>>>>>>>> >https://groups.google.com/d/msgid/ops4j/e9d0b4ab-33d7-4895-8a0f-e6d55e3e3b43n%40googlegroups.com >>>>>>>>> ><https://groups.google.com/d/msgid/ops4j/e9d0b4ab-33d7-4895-8a0f-e6d55e3e3b43n%40googlegroups.com?utm_medium=email&utm_source=footer>. >>>>>>>>> >>>>>>>>> >>>>>>>> -- >>>>>>>> -- >>>>>>>> ------------------ >>>>>>>> OPS4J - http://www.ops4j.org - [email protected] >>>>>>>> >>>>>>>> --- >>>>>>>> You received this message because you are subscribed to the >Google >>>>>>>> Groups "OPS4J" group. >>>>>>>> To unsubscribe from this group and stop receiving emails from >it, >>>>>>>> send an email to [email protected]. >>>>>>>> >>>>>>> To view this discussion on the web visit >>>>>>>> >https://groups.google.com/d/msgid/ops4j/CAAdXmhqcqH3h1bhJhYLb1%2B08u3dcSzFE%2BEYpe%2B62O7CbmMZHGQ%40mail.gmail.com >>>>>>>> ><https://groups.google.com/d/msgid/ops4j/CAAdXmhqcqH3h1bhJhYLb1%2B08u3dcSzFE%2BEYpe%2B62O7CbmMZHGQ%40mail.gmail.com?utm_medium=email&utm_source=footer>. >>>>>>>> >>>>>>>> >>>>>>> -- >>>>>> -- >>>>>> ------------------ >>>>>> OPS4J - 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