Re: [jetty-users] bootstrapping jetty-plus from eclipse equinox: classl

[Hugues Malphettes <hmalphettes@xxxxxxxxxxx>]

Hi Jan,
thanks for pointing me to the new packaging.

I have updated the sample project to use jetty-7.0.0.RC5 and identified one trivial bug (bug #289285).

The goal of this experiment is to bootstrap the entire jetty distribution directly from osgi.
This includes starting jetty using the usual xml configuration files.
I am hoping that this will provide a smooth migration to OSGi for traditional j2ee-webapps: they can execute their webapps without any change at all. The configuration of jetty remains also identical.
This also takes full advantage of eclipse-PDE; web-applications are entirely self-contained inside an OSGI-bundle that is developed in the PDE: compile and debug without involving an external build script, a deployment tool and a remote debugger.

Most of the other cases where jetty is embedded in OSGi do not have the issue identified here for these reasons:
- they implement the HttpService of OSGi where they don't use jetty-plus at all: for example equinox's HttpService.
- they place jetty's bundles inside the root-classloader: for example nuxeo.
- they have re-packaged jetty's bundles themselves to make sure that all bundles are able to locate classes directly from each other. For example using Eclipse-BuddyPolicy and similar techniques.

So here is what happen: once all the jetty libraries are loaded by equinox jetty is started like this:
            _server = new Server();
            XmlConfiguration config = new XmlConfiguration(new FileInputStream(
                    System.getProperty("jetty.home") + "/etc/jetty.xml")) {
                
            };
            config.configure(_server);
            _server.start();

This fails because org.eclipse.jetty.util's classloader is not able to load classes inside the org.eclipse.jetty.server bundle:
java.lang.ClassNotFoundException: org.eclipse.jetty.server.Server
    at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
    at org.eclipse.core.runtime.internal.adaptor.ContextFinder.loadClass(ContextFinder.java:129)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
    at org.eclipse.jetty.util.Loader.loadClass(Loader.java:90)
    at org.eclipse.jetty.xml.XmlConfiguration.nodeClass(XmlConfiguration.java:224)
    at org.eclipse.jetty.xml.XmlConfiguration.configure(XmlConfiguration.java:187)
    at org.intalio.osgi.jetty.server.JettyBootstrapActivator.start(JettyBootstrapActivator.java:70)
    at org.eclipse.osgi.framework.internal.core.BundleContextImpl$1.run(BundleContextImpl.java:782)

org.eclipse.jetty.server depends on org.eclipse.jetty.util but not the other way round;
org.eclipse.jetty.util is in charge of loading org.eclipse.jetty.server.Server but does not import the relevant package and neither does it depend on the bundle. 

The workaround I was suggesting was to add headers to the manifest so that the class-resolution happens anyways.
However it is not great. Maybe some extra options to be able to pass the classloader to use to XmlConfiguration ?

My apologies for the long email,
Cheers,
Hugues
PS I placed some screenshots of the PDE setup: http://github.com/hmalphettes/osgi-webapp-simple/tree/cfe791f2b395930c0de95248b69f3f1bff4aab4c/setup-screenshots

On Sat, Sep 12, 2009 at 9:41 AM, Hugues Malphettes <hmalphettes@xxxxxxxxxxx> wrote:

Thanks Jan, I am following your advice and will keep you updated.
Hugues

On Fri, Sep 11, 2009 at 8:12 PM, Jan Bartel <janb@xxxxxxxxxxx> wrote:
> Hugues,
>
> Will take a look at the demo project to see the issue (thanks
> for providing that, makes things much easier).
>
> Meanwhile, from the org.mortbay.* packaging, I guess you're using jetty-6.
>  I recommend that you target the jetty-7 releases from eclipse (which are
> under the org.eclipse package) as jetty-7 has
> been refactored to be (even more) componentized.
> Jetty has been used successfully in osgi containers, so I'll be
> interested to see why your use case has a problem. Our goal is to
> make jetty as osgi-friendly as possible, so we're interested in
> feedback to help improve it.
>
> thanks
> Jan
>
>
>
> Hugues Malphettes wrote:
>>
>> Hi there,
>>
>> I am having difficulties using org.mortbay.jetty,
>> org.mortbay.jetty.util, org.mortbay.jetty.plus and org.mortbay.naming
>> together in an osgi container.
>> the issue is that when I start the jetty server and configure it with
>> jetty.xml and jetty-plus.xml from the osgi container, equinox fails.
>>
>> The classloader of the org.mortbay.jetty.server bundle is not able to
>> locate the jetty-plus classes:
>> when jetty tries to load
>>  <Item>org.mortbay.jetty.plus.webapp.EnvConfiguration</Item>
>>  <Item>org.mortbay.jetty.plus.webapp.Configuration</Item>
>> it fails.
>>
>> The best workaround I am using consists of modifying the manifests of
>> org.mortbay.jetty.server, org.mortbay.jetty.plus and
>> org.mortbay.naming to resolve this.
>> I added to org.mortbay.jetty.server:
>>     Eclipse-BuddyPolicy: registered
>> And to the manifests of org.mortbay.jetty.plus and org.mortbay.naming:
>>     Eclipse-RegisterBuddy: org.mortbay.jetty.server
>>
>> We could also consider making org.mortbay.jetty.server,
>> org.mortbay.jetty.plus and org.mortbay.naming fragments that target
>> org.mortbay.jetty.server. A bit more osgi compliant. But not many osgi
>> container support fragments yet.
>>
>> Here is a small project to reproduce the issue:
>> http://github.com/hmalphettes/osgi-webapp-simple/tree/master (licensed
>> under the EPL)
>> The first bundle bootstraps jetty.
>> The second one is a bundle that contains a web-application.
>> It works fine because it depends only on jetty, not jetty-plus.
>> Adding jetty-plus's bundle and using jetty-plus in the config will
>> reproduce the issue described above.
>>
>> Let me know if I am missing something or if there is a different way
>> to install jetty' plus bundles in an osgi container.
>>
>> Cheers,
>> Hugues
>> _______________________________________________
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>> jetty-users@xxxxxxxxxxx
>> https://dev.eclipse.org/mailman/listinfo/jetty-users
>
> --
> Jan Bartel, Webtide LLC | janb@xxxxxxxxxxx | http://www.webtide.com
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