I usually do it like this:
1) make Activator extend the DependencyActivatorBase (from the Dependency
manager (from apache felix))
you'll be required to implement (a.o.) an init() method; The following would be
a good start:
public void init(BundleContext context, DependencyManager manager)
throws Exception {
Service svc = createService()
.setImplementation(MainServlet.class)
.add(createServiceDependency()
.setService(HttpService.class)
.setRequired(true))
.add(createServiceDependency()
.setService(EventAdmin.class)
.setRequired(true));
svc.start();
}
the code above sets in motion quite a lot:
* The dependency manager takes care of automatic instantiation of the
"MainServlet".
This is only done when both the HttpService and (e.g.) the EventAdmin
service can be obtained from the OSGi framework.
* It then tries to invoke init() on the MainServlet instance (if available)
* It then injects the above mentioned OSGi services into the corresponding
fields.
e.g:
public class MainServlet extends HttpServlet {
//dependency managed
private HttpService m_server;
//dependency managed
private EventAdmin m_admin;
//dependency managed
private BundleContext m_context;
}
would suffice.
* It then tries to invoke start() on the MainServlet instance (if available)
Notice that both m_server and m_admin are now available to the
MainsServlet code !
Since this is an excellent moment to register the servlet, I propose to do that
here:
private void start() throws ServletException, NamespaceException {
m_server.registerServlet("/main", this, null, null);
}
* At any time in the future, a required dependency might disappear from the
framework. Then this servlet
is obviously (your decision) not able to perform its functionality anymore.
It then needs to be unregistered.
The dependency manager can again do that for you: just before the service it
depends on is deregistered
we get 'notified': the dep.man will try to invoke: stop()
e.g.
private void stop() {
m_server.unregister("/main");
}
would do the trick for you.
As soon as the services this servlet depends on have all reappeared, the dep.
man. will again call "start()"
so the servlet gets registered again.
2) well, there's no "2" ;-) your doGet() method can now make use of the
injected OSGi services without any checks.
Does the above provide you with a pattern you feel comfortable with ?
Cheers, Dennis
On 08-01-09 22:10, "BJ Hargrave" <hargr...@us.ibm.com> wrote:
Well you have to construct your Servlet objects to register them with the
HttpService. Why not pass the BundleContext to the Servlet object during
construction or shortly thereafter but before you register the Servlet object.
--
No trees were killed in the sending of this message. However, a large number of
electrons were terribly disturbed!
-------------------------------------------------
Dennis Geurts
software development luminis
K.v.k Centraal Gelderland: 09 16 28 87
-------------------------------------------------
+31 6 12078236
dennis.geu...@luminis.nl
www.luminis.nl
-------------------------------------------------
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