A few things.
You seem to be grasping at straws in your code.
First, you'll need a proper set of WebAppContext configurations (declared all of them, in the correct order)
context.setConfigurations(new Configuration[]
{
new AnnotationConfiguration(),
new WebInfConfiguration(),
new WebXmlConfiguration(),
new MetaInfConfiguration(),
new FragmentConfiguration(),
new EnvConfiguration(),
new PlusConfiguration(),
new JettyWebXmlConfiguration()
});
Next, you'll require jetty-annotations.jar (and transitive dependencies) in your environment too.
After that, you'll need to make sure that the following are in your WEB-INF/lib directories
The spring jar(s) that contains the classes:
Make sure these are only in your webapp's WEB-INF/lib directory.
Then, all of your classes that implement WebApplicationInitializer should be in WEB-INF/classes/ or WEB-INF/lib/
That should be it.
What happens is Jetty scans all of your container jars, then WEB-INF/lib jars, then WEB-INF/classes files.
In the process, it sees that WEB-INF/lib/spring-something.jar has a resource called META-INF/services/javax.servlet.ServletContainerInitializer
Jetty will see the @HandlesType(WebApplicationInitializer.class) on that ServletContainerInitializer and call the standard
At this point, Jetty is out of the equation and Spring is doing the rest of the initialization for itself.
Good luck