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From "Arshad Mahmood" <arsh...@compuvision.co.uk>
Subject Re: JNDI with a custom factory not working
Date Thu, 13 Jun 2002 17:11:38 GMT

----- Original Message -----
From: "Remy Maucherat" <remm@apache.org>
To: "Tomcat Developers List" <tomcat-dev@jakarta.apache.org>
Sent: Thursday, June 13, 2002 5:33 PM
Subject: Re: JNDI with a custom factory not working


> Arshad Mahmood wrote:
> > ----- Original Message -----
> > From: "Ian Darwin" <ian@darwinsys.com>
> > To: "Tomcat Developers List" <tomcat-dev@jakarta.apache.org>; "Arshad
> > Mahmood" <arshadm@compuvision.co.uk>
> > Sent: Thursday, June 13, 2002 1:48 AM
> > Subject: Re: JNDI with a custom factory not working
> >
> >
> >
> >>On June 12, 2002 07:45 am, Arshad Mahmood wrote:
> >>
> >>>I am having a problem trying to use a custom factory with JNDI. I get
an
> >>>exception froom org.apache.naming.factory.ResourceFactory. I have added
> >>>debug and it appears that my "factory" parameter is not being picked up
> >>>from the server.xml.
> >>>
> >>>Can somebody familiar with the naming code point me to the classes I
> >>
> > need
> >
> >>>to look at to trace this problem. Alternatively, if somebody can
confirm
> >>>that the JNDI-Howto example for a custom beanFactory works correctly in
> >>
> > 4.1
> >
> >>>(I have tried it and it doesn't) then I will look at my configuration
> >>>again.
> >>
> >>Doesn't work for me either. Inserting a listBindings() call for
> >
> > java:comp/env/bean
> >
> >>reveals nothing bound there.
> >
> >
> > I have traced the problem a little further and I think I know what the
> > problem is but I haven't got a clue how to fix it.
> >
> > Basically, it appears that a different NamingContext is created per
> > thread/class loader. Let's assume that you have a tomcat instance called
> > "Standalone", a virtual host "localhost" and a context "myapp".
> >
> > If you define any JNDI resources in the server.xml, then they appear to
be
> > put into a naming context call "//Standalone/myapp". Your resource
> > definitions in the web.xml go into the "//Standalone/localhost/myapp"
> > context.
> >
> > If you attempt to read the resources from your servlet then the
> > "//Standalone/localhost/myapp" context is used, this is ok for jdbc, etc
> > because the factory is hardwired into the naming code. But if you have
> > defined a custom factory then no definition exists in this context for
that
> > (because it's been put into the "//Standalone/myapp" context). I believe
> > this also goes for any parameters that you have defined.
> >
> > The fix would appear to be for Tomcat to put the resources under the
virtual
> > in the first place for those defined in the server.xml. There is still
an
> > issue though for the "global resources" as I am not sure you can link to
> > them because they are under a different naming context.
> >
> > This is an initial investigation so my analysis may be FLAWED.
> >
> > Remy, does this explanation of how the naming contexts are defined/used
make
> > sense ?
>
> I'm not sure I understand very well, so I'll assume it's a problem with
> the links.
>
> The global resources defined in server.xml are not accessible by default
> in the web applications (because you may want to restrict some to
> specific webapps, etc). So you have to link them using a ResourceLink
> element. You can also define the resource links in the default context
> so that all your contexts in your host or engine will have the link,
> instead of having to define it in each one.
> The admin webapp will have full support for this shortly (I reckon that
> configuring this is *hard* at the moment).
>
> Remy

Remy,

Thanks for you response. I didn't make myself very clear, I'll try again.

The Problem
=========

In the server.xml have defined a global resourcce under the name
"rohas/filecache".
The resource params defines a "factory" along with other attributes.
In my context I have defined a "ResourceLink" that maps to the
global name (I have given them both the same name, I assume that
doesn't make a difference).

In the web.xml for my application I have defined a "resource-ref" that
points to this resource.

When I try and access the resource via an InitialContext in the "init"
function of my servlet,
I get a NamingException from
org.apache.naming.factory.ResourceFactory.getObjectInstance.

To look into the problem I put some debug into the
"org.apache.naming.NamingContext" class in the
lookup method.

I noticed that when this class was called a few times, the "name" member
varied between "//Standalone/myapp" amd
"//Standalone/localhost/myapp", etc.

I was a bit surprised because I thought when I asked "java:comp/env" I would
always get the same "NamingContext" and
not different ones.

I then traced the code through
"org.apache.naming.java.javaURLContextFactory", which in turn uses
"org.apache.naming.SelectorContext".

The SelectorConext class uses "getBoundContext" to retrieve the appropriate
NamingContext to which it delegated
the lookup/bind/unbind, etc.

The getBoundContext then uses ContextBindings.getContext to get the context
(if doesn't exist then it creates a new one).
*** IMPORTANT *** The member variable initialContext is overriden inside the
"if" of this function (is this intentional).

ContextBindings appears to return a NamingContext based on the class loader
currenty in used. Hence the multiple contexts and why the name I am looking
for doesn't appear in the context which I am using for lookup.

Regards,
Arshad



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