Cannot access a EJB 3.0 bean from a servlet

[Prasad Kashyap <go...@gmail.com>]

The easiest way to reference a 3.0 EJB is by dependency injection
(@EJB). But we don't have annotations working in servlets yet. So if
we go back to doing the traditional way of a lookup, we would have to
declare a <ejb-ref> in the web.xml

Even if the annotations are processed, they write an <ejb-ref> element
in the web.xml.

However for a 3.0 EJB, the interface elements like <home>, <local> etc
are not applicable inside a <ejb-ref>. So they are (should be)
omitted. Here is the schema:
http://java.sun.com/xml/ns/javaee/javaee_5.xsd

But our deployer has a hard requirement on those interfaces. It fails
to deploy the module.
Here is the stack trace excerpt: http://rifers.org/paste/show/3344

Here is the jira for this problem:
http://issues.apache.org/jira/browse/GERONIMO-2778

Cheers
Prasad

Re: Cannot access a EJB 3.0 bean from a servlet

[David Blevins <da...@visi.com>]

Alright, so I figured out how to fix the naming code so that it will  
work for business interfaces as well as references from servlets to  
ejb for business interfaces.  Dain is hacking it in now.

On Jan 23, 2007, at 11:49 AM, Prasad Kashyap wrote:

> The easiest way to reference a 3.0 EJB is by dependency injection
> (@EJB). But we don't have annotations working in servlets yet. So if
> we go back to doing the traditional way of a lookup, we would have to
> declare a <ejb-ref> in the web.xml
>
> Even if the annotations are processed, they write an <ejb-ref> element
> in the web.xml.
>
> However for a 3.0 EJB, the interface elements like <home>, <local> etc
> are not applicable inside a <ejb-ref>. So they are (should be)
> omitted. Here is the schema:
> http://java.sun.com/xml/ns/javaee/javaee_5.xsd

This isn't exactly right.  Those elements are still very applicable.   
For a proper ejb-ref to an EJB 3.0 bean (i.e. a business interface)  
it *must* have the <remote> or <local> and must *not* have the <home>  
or <local-home>.

These can only be omitted in the case of dependency injection where  
the code using the @EJB to generate a metadata-complete ejb-ref  
should *always* fill in the <remote> element of the <ejb-ref>  
element.  If the user does not specify the 'beanInterface' attribute  
of the @EJB annotation, then the code building the reference must use  
the class type of the field or method as the value of '<remote>'.

There is an edge case where you truly do not know if the @EJB is  
pointing to a local object or a remote object and therefore don't  
know whether to build a ejb-ref or an ejb-local-ref.  For OpenEJB we  
build an ejb-ref and flag it as being "ambiguous", then in the jndi  
building code we try to resolve it against the full list of available  
ejbs.  We'll have to figure out some way to communicate this edge  
case to the ejb naming builder so we can deal with it.

> But our deployer has a hard requirement on those interfaces. It fails
> to deploy the module.
> Here is the stack trace excerpt: http://rifers.org/paste/show/3344

Dain should have this code fixed up soon.  It'll work as long as the  
code building the ejb-ref for the servlet follows the rules I state  
above.

> Here is the jira for this problem:
> http://issues.apache.org/jira/browse/GERONIMO-2778

Thanks.  I'm going to change the description of that jira issue to  
reflect that <local> or <remote> *should* be filled in before the ejb  
naming builder is invoked.  I don't know where that code is, perhaps  
Tim knows.

-David