Re: [jetty-users] Bad __context set in WebAppContext.start sequence with

[Henning Blohm <henning.blohm@xxxxxxxxxx>]

Great!

Thanks,
Henning

On 09/19/2012 11:32 PM, Jan Bartel wrote:

Hi Henning,

That looks like a genuine bug to me!

I opened https://bugs.eclipse.org/bugs/show_bug.cgi?id=389956

I'll take a look at this today.

Jan

On 19 September 2012 00:21, Henning Blohm <henning.blohm@xxxxxxxxxx> wrote:

We are embedding Jetty and today we noticed the following not quite trivial
bug in Jetty's start handling for Web apps.

This bug was observed on Jetty 8.1.4 and as far as I can tell the relevant
code has not changed since then. It happens when you start a WebAppContext
from within a running Web app, i.e. while processing a request. In our
scenario, a Web app may be started on-demand and the trigger to do so may
occur while in a Web app.

I checked with Jetty 6.1.22 (old integration) and it works ok there - I did
not debug it all the way through to see why it works there and not in 8.1.4.

Here is what happens:

When calling WebAppContext.start() you end up in WebAppContext.doStart()
which has this control flow:

preConfigure();
super.doStart();
postConfigure();

In preConfigure, eventually EnvConfiguration.preConfigure(<context>) is
called and that is setting up the JNDI ENC.

And here is where ContextFactory comes into the game:

When looking for the class loader to identify a "java:comp" ENC from,
ContextFactory.getObjectInstance first consults
ContextHandler.getCurrentContext(). Only if that returns null, the current
thread's context class loader is considered.

However, the switch of Jetty Contexts in ContextHandler is done in
ContextHandler.doStart(), i.e. only after the call to preConfigure() in
WebAppContext.doStart().

Now, if you are not in a Web App and you want to start a WebAppContext and
the current thread's context classloader is set, then
ContextHandler.getCurrentContext()==null and you get an ENC for the new Web
App as expected.

But if you are currently processing a Web app request, then
ContextHandler.doScope will have set that Web app's context and
ContextHandler.getCurrentContext()!=null and ContextFactory will try to
create an ENC for a loader that already has one and you get:

Caused by: javax.naming.NamingException: This context is immutable;
remaining name 'env'
   at
org.eclipse.jetty.jndi.NamingContext.createSubcontext(NamingContext.java:302)
   at
org.eclipse.jetty.jndi.NamingContext.createSubcontext(NamingContext.java:383)
   at
org.eclipse.jetty.plus.webapp.EnvConfiguration.createEnvContext(EnvConfiguration.java:253)
   at
org.eclipse.jetty.plus.webapp.EnvConfiguration.preConfigure(EnvConfiguration.java:67)
   at
org.eclipse.jetty.webapp.WebAppContext.preConfigure(WebAppContext.java:430)
   at org.eclipse.jetty.webapp.WebAppContext.doStart(WebAppContext.java:466)
   at
org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)

Please let me know, if there is some way of getting around this. Hope there
was sufficient details and sorry for the complex case.

Thanks,
  Henning
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