Hi all,
I've been looking for info on this topic with no avail.
I'm currently using PAX-Web (Pax Web - WAR Extender) to run a number of
servlets in a WAB. I'm working on Equinox. Legacy code used programmatic
service lookup to access other OSGi services (Service Tracker) but I've
refactored most of the code base to use Declarative Services instead. (that
solved several start-up order issues in the process)
My issue is that Declarative Services dependency injection is not working
with PAX-Web loaded servlets. If I include a OSGI-INF/service.xml file
declaring the servlet dependencies, the class is loaded twice: Once by DS
and once by PAX-WEB. Logically, only the class loaded by DS is injected
with any dependencies declared.
DS:
at org.eclipse.equinox.internal.ds.model.ServiceComponent.*createInstance*
(ServiceComponent.java:480)
at
org.eclipse.equinox.internal.ds.model.ServiceComponentProp.createInstance(ServiceComponentProp.java:271)
at
org.eclipse.equinox.internal.ds.model.ServiceComponentProp.build(ServiceComponentProp.java:332)
at
org.eclipse.equinox.internal.ds.InstanceProcess.buildComponent(InstanceProcess.java:588)
at
org.eclipse.equinox.internal.ds.InstanceProcess.buildComponents(InstanceProcess.java:196)
at org.eclipse.equinox.internal.ds.Resolver.getEligible(Resolver.java:328)
at
org.eclipse.equinox.internal.ds.SCRManager.serviceChanged(SCRManager.java:221
PAX-WEB:
at org.ops4j.pax.web.extender.war.internal.RegisterWebAppVisitorHS.*
newInstance*(RegisterWebAppVisitorHS.java:225)
at
org.ops4j.pax.web.extender.war.internal.RegisterWebAppVisitorWC.visit(RegisterWebAppVisitorWC.java:202)
at
org.ops4j.pax.web.extender.war.internal.model.WebApp.accept(WebApp.java:583)
at
org.ops4j.pax.web.extender.war.internal.WebAppPublisher$HttpServiceListener.register(WebAppPublisher.java:170)
at
org.ops4j.pax.web.extender.war.internal.WebAppPublisher$HttpServiceListener.serviceChanged(WebAppPublisher.java:155)
at
org.ops4j.pax.web.extender.war.internal.WebAppPublisher$HttpServiceListener.serviceChanged(WebAppPublisher.java:119)
at
org.ops4j.pax.swissbox.tracker.ReplaceableService.setService(ReplaceableService.java:114)
at
org.ops4j.pax.swissbox.tracker.ReplaceableService.access$100(ReplaceableService.java:28)
at
org.ops4j.pax.swissbox.tracker.ReplaceableService$CollectionListener.serviceAdded(ReplaceableService.java:183)
at
org.ops4j.pax.swissbox.tracker.ServiceCollection$Tracker.addingService(ServiceCollection.java:181)
I worked around this situation by declaring the references to the services
static and synchronizing the access (not very nice. Might impact
performance),
eg.
public synchronized void onServiceUp(FooService svc) {
ClassImpl.fooService = svc;
}
but I've a situation now where I do need an instance of a service injected
for each servlet instance created, so the synchronized hack approach won't
work.
I also tried to declare the servlet and its dependecies using the OSGi way,
by declaring this servlet to offer a javax.servlet.Servlet service:
[ <property name="alias" type="String" value="/main/fooservice"/>
<property name="servlet-name" type="String" value="FooServlet"/ -->
<service>
<provide interface="javax.servlet.Servlet"/>
</service>]
But given that the servlet is also in the WAR, PAX-Web finds it and tries
to register it, resulting in a 'WAR: Http context already used' like
described here:
http://www.mail-archive.com/general@lists.ops4j.org/msg11221.html
So, to summarize my question: Is there a correct/recommended way to use
Declarative Services (DS) with Pax Web- War extender and if so, what are
the best practices?
Many thanks,
Gerard.
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