This happens if the EAR has a persistence.xml file in it's META-INF directory.
ERROR OpenEJB.startup - OpenEJB has encountered a fatal error and cannot be started: Assembler failed to build the container system. org.apache.openejb.OpenEJBException: java.lang.ClassCastException: java.net.URL cannot be cast to java.util.List: java.net.URL cannot be cast to java.util.List at org.apache.openejb.assembler.classic.Assembler.build(Assembler.java:478) at org.apache.openejb.OpenEJB$Instance.<init>(OpenEJB.java:150) at org.apache.openejb.OpenEJB.init(OpenEJB.java:298) at org.apache.tomee.catalina.TomcatLoader.initialize(TomcatLoader.java:259) at org.apache.tomee.catalina.ServerListener.lifecycleEvent(ServerListener.java:159) at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117) at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90) at org.apache.catalina.util.LifecycleBase.setStateInternal(LifecycleBase.java:402) at org.apache.catalina.util.LifecycleBase.init(LifecycleBase.java:110) at org.apache.catalina.startup.Catalina.load(Catalina.java:576) at org.apache.catalina.startup.Catalina.load(Catalina.java:599) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:497) at org.apache.catalina.startup.Bootstrap.load(Bootstrap.java:310) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:484) Caused by: java.lang.ClassCastException: java.net.URL cannot be cast to java.util.List at org.apache.openejb.config.DeploymentLoader.addWebModule(DeploymentLoader.java:830) at org.apache.openejb.config.DeploymentLoader.addWebModule(DeploymentLoader.java:819) at org.apache.openejb.config.DeploymentLoader.createAppModule(DeploymentLoader.java:629) at org.apache.openejb.config.DeploymentLoader.load(DeploymentLoader.java:164) at org.apache.openejb.config.ConfigurationFactory.configureApplication(ConfigurationFactory.java:822) at org.apache.openejb.config.ConfigurationFactory.getOpenEjbConfiguration(ConfigurationFactory.java:525) at org.apache.openejb.config.ConfigurationFactory.getOpenEjbConfiguration(ConfigurationFactory.java:606) at org.apache.openejb.assembler.classic.Assembler.getOpenEjbConfiguration(Assembler.java:485) at org.apache.openejb.assembler.classic.Assembler.build(Assembler.java:464) ... 16 common frames omitted
