I'm working on externalizing the class loader construction to the new deployer layer, but there are assumptions being made regarding URLClassLoaders. For example, in org.apache.jasper.compiler.JspRuntimeContext:

15:14:45,816 INFO [TomcatDeployment] deploy, ctxPath=/invoker, vfsUrl=http-invoker.sar/invoker.war
15:14:47,655 ERROR [[/invoker]] StandardWrapper.Throwable
java.lang.ClassCastException: org.jboss.classloader.spi.base.BaseClassLoader
 at org.apache.jasper.compiler.JspRuntimeContext.<init>(JspRuntimeContext.java:113)
 at org.apache.jasper.servlet.JspServlet.init(JspServlet.java:101)
 at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1048)
 at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:950)
 at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContext.java:4072)
 at org.apache.catalina.core.StandardContext.start(StandardContext.java:4377)
 at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:791)
 at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:771)
 at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:525)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:585)
 at org.apache.tomcat.util.modeler.BaseModelMBean.invoke(BaseModelMBean.java:297)
 at org.jboss.mx.server.RawDynamicInvoker.invoke(RawDynamicInvoker.java:164)
 at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:668) at org.apache.catalina.core.StandardContext.init(StandardContext.java:5357)
 at org.jboss.web.tomcat.service.deployers.TomcatDeployment.performDeployInternal(TomcatDeployment.java:350)

code:

 public JspRuntimeContext(ServletContext context, Options options) {

 this.context = context;
 this.options = options;

 // Get the parent class loader
 parentClassLoader =
 (URLClassLoader) Thread.currentThread().getContextClassLoader();
 if (parentClassLoader == null) {
 parentClassLoader =
 (URLClassLoader)this.getClass().getClassLoader();
 }

This is only used for the compile classpath. I thought this was only used for the legacy javac style compiler, not the jdt memory based compiler. If that is the case this behavior needs to be suppressed when the jdt compiler is being used.