[weld-dev] @Resource annotation handling by Weld vs Servlet container
Jan Bartel
janb at intalio.com
Mon Apr 13 18:41:50 EDT 2015
Jozef,
>> Looking at the WeldServletLifecyle class on line 124, it will always
>> provide an implementation of the ResourceInjectionServices (an
>> instance of ServletResourceInjectionServices). If we were to provide
>> our own implementation of ResourceInjectionServices, how would we
>> override that one? Is there a way to get a hold of the Deployment and
>> thus the BeanDeploymentArchives so we could set our own implementation
>> up? Ideally we'd like a pure CDI api way of interacting with weld, but
>> maybe that's not possible in this case?
>
> You need to interact with Weld APIs to do this. A service can be overridden
> using ServiceLoader mechanism. See
> http://docs.jboss.org/weld/reference/2.2.10.Final/en-US/html/ri-spi.html#_registering_services
> for details.
Ok, great, I'll give this a go and report back.
>> Alternatively, instead of Weld
>>>
>>> hooking into lifecycle of Jetty-managed components, Jetty could use CDI
>>> APIs
>>> to perform CDI injection on instances it manages.
>>>
>> Yes, potentially we could do that, although we'd probably need your
>> guidance on the best way to do that. Can @Resource be used by pojo
>> beans or only by servlet artifacts (servlet/filter/listeners)? If the
>> latter, then I'm fine for Jetty to do all the handling of @Resource.
>> If not, then it probably makes sense for weld to handle it, and we'd
>> need a way to disable Jetty's implementation if weld is present in a
>> webapp ...
>
> I think the best approach would be to modify the integrating decorator to
> only provide CDI injection to Jetty-managed instances. I have implemented it
> here:
> https://github.com/weld/core/commit/f7420e34355c5c82ef516713c65fc6cd750fb651
So if jetty is handling @Resource (handling making the jndi entries
and injecting the fields/methods) for servlets/filters/listeners, what
will happen if someone declares this in eg a servlet:
public class MyServlet extends HttpServlet
{
@Producer @Resource (name="foo")
@MyDb
private DataSource db;
}
Will weld still inspect this class and find the producer and make it
available for injection in other code?
cheers
Jan
>
>>
>> cheers
>> Jan
>>
>>> Additional comments inline:
>>>
>>>
>>> On 04/10/2015 02:00 AM, Jan Bartel wrote:
>>>>
>>>> Hi Weld developers,
>>>>
>>>> The Jetty project is looking at how we can do a tighter integration
>>>> with Weld, also with a view to discussions in the Servlet Spec 4
>>>> committee to alleviate the necessity for CDI implementations to
>>>> maintain jetty-specific initialisation code.
>>>>
>>>> During investigations, I noticed that we seem to have a conflict in
>>>> the handling of a few annotations for classes that are managed by the
>>>> servlet container (ie servlets, filters, listeners etc):
>>>>
>>>> @Resource
>>>> @PostConstruct
>>>> @PreDestroy
>>>>
>>>> As Jetty puts a servlet/filter/listener into service, we introspect
>>>> the class and find the above annotations and process them. It seems
>>>> that Weld does too, as I see the following failure for this code
>>>> snippet:
>>>>
>>>> public class TestListener implements ServletContextListener
>>>> {
>>>> @Resource(mappedName="maxAmount")
>>>> private Double maxAmount;
>>>> }
>>>>
>>>>
>>>> javax.naming.NameNotFoundException; remaining name 'maxAmount'
>>>> at
>>>>
>>>> org.eclipse.jetty.jndi.local.localContextRoot.lookup(localContextRoot.java:429)
>>>> at
>>>>
>>>> org.eclipse.jetty.jndi.local.localContextRoot.lookup(localContextRoot.java:533)
>>>> at javax.naming.InitialContext.lookup(InitialContext.java:411)
>>>> at
>>>>
>>>> org.jboss.weld.injection.spi.helpers.AbstractResourceServices.resolveResource(AbstractResourceServices.java:48)
>>>> at
>>>>
>>>> org.jboss.weld.injection.spi.helpers.AbstractResourceServices$1.createResource(AbstractResourceServices.java:121)
>>>> at
>>>>
>>>> org.jboss.weld.injection.AbstractResourceInjection.getResourceReference(AbstractResourceInjection.java:44)
>>>> at
>>>>
>>>> org.jboss.weld.injection.AbstractResourceInjection.injectResourceReference(AbstractResourceInjection.java:53)
>>>> at org.jboss.weld.util.Beans.injectEEFields(Beans.java:344)
>>>> at
>>>>
>>>> org.jboss.weld.injection.producer.ResourceInjector$1.proceed(ResourceInjector.java:69)
>>>> at
>>>>
>>>> org.jboss.weld.injection.InjectionContextImpl.run(InjectionContextImpl.java:48)
>>>> at
>>>>
>>>> org.jboss.weld.injection.producer.ResourceInjector.inject(ResourceInjector.java:72)
>>>> at
>>>>
>>>> org.jboss.weld.injection.producer.BasicInjectionTarget.inject(BasicInjectionTarget.java:121)
>>>> at
>>>>
>>>> org.jboss.weld.environment.servlet.inject.AbstractInjector.inject(AbstractInjector.java:55)
>>>> at
>>>>
>>>> org.jboss.weld.environment.jetty.JettyWeldInjector.inject(JettyWeldInjector.java:15)
>>>> at
>>>>
>>>> org.jboss.weld.environment.jetty.WeldDecorator.decorate(WeldDecorator.java:105)
>>>> at
>>>>
>>>> org.eclipse.jetty.util.DecoratedObjectFactory.decorate(DecoratedObjectFactory.java:77)
>>>> at
>>>>
>>>> org.eclipse.jetty.servlet.ServletContextHandler.startContext(ServletContextHandler.java:335)
>>>> at
>>>>
>>>> org.eclipse.jetty.webapp.WebAppContext.startWebapp(WebAppContext.java:1349)
>>>> at
>>>>
>>>> org.eclipse.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1342)
>>>> at
>>>>
>>>> org.eclipse.jetty.server.handler.ContextHandler.doStart(ContextHandler.java:743)
>>>> at
>>>>
>>>> org.eclipse.jetty.servlet.ServletContextHandler.doStart(ServletContextHandler.java:257)
>>>> at
>>>> org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:505)
>>>>
>>>>
>>>> Googling around, it is not clear to me exactly which of the Common
>>>> Annotations (JSR250) that Weld supports and I'd appreciate some input
>>>> from the Weld devs in order for Jetty to work out how best to move
>>>> forward with Weld integration.
>>>>
>>>> In particular, I'd appreciate some clear feedback on which of the
>>>> following @Resource annotation usages will be handled by Weld:
>>>>
>>>> @Resource on a class
>>>> @Resource on a field
>>>> @Resource on a method
>>>> @Resource annotations without an accompanying @Producer annotation
>>>
>>> @Resource on a field (with or without @Producer), @Resource on a method,
>>> @PostConstruct and @PreDestroy are handled by Weld on a managed instance
>>> (generally).
>>>>
>>>>
>>>> Secondly, as can be seen from the stacktrace above, Weld is failing to
>>>> find the matching JNDI entry for an @Resource annotation. This is
>>>> because Weld appears not to be looking in "java:comp/env" namespace,
>>>> although IIRC that is mandated by the JavaEE spec for EE managed
>>>> classes (servlets/filters/listeners etc). So if Jetty delegates
>>>> handling of some/all processing of @Resource, how do we ensure that
>>>> Weld will be able to find the right JNDI entry?
>>>
>>> This might be a bug in weld-servlet's ResourceInjectionServices
>>> implementation. Can you file an issue at
>>> https://issues.jboss.org/browse/WELD ?
>>>
>>>> thanks for your time,
>>>> Jan
>>>
>>>
>>
>>
>
--
Jan Bartel <janb at intalio.com>
www.webtide.com
'Expert Jetty/CometD developer,production,operations advice'
More information about the weld-dev
mailing list