HTTP Status 500 - 
type Exception report

message 

description The server encountered an internal error () that prevented it from fulfilling this request.

exception 

javax.servlet.ServletException: Unable to retrieve EntityManagerFactory for unitName mbcolfromdbPU
	javax.faces.webapp.FacesServlet.service(FacesServlet.java:256)
	com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:73)
	com.sun.enterprise.web.VirtualServerPipeline.invoke(VirtualServerPipeline.java:120)
	org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:231)
	com.sun.enterprise.web.connector.grizzly.ProcessorTask.invokeAdapter(ProcessorTask.java:667)
	com.sun.enterprise.web.connector.grizzly.ProcessorTask.processNonBlocked(ProcessorTask.java:574)
	com.sun.enterprise.web.connector.grizzly.ProcessorTask.process(ProcessorTask.java:844)
	com.sun.enterprise.web.connector.grizzly.ReadTask.executeProcessorTask(ReadTask.java:287)
	com.sun.enterprise.web.connector.grizzly.ReadTask.doTask(ReadTask.java:212)
	com.sun.enterprise.web.connector.grizzly.TaskBase.run(TaskBase.java:252)
	com.sun.enterprise.web.connector.grizzly.WorkerThread.run(WorkerThread.java:75)


root cause 

java.lang.IllegalStateException: Unable to retrieve EntityManagerFactory for unitName mbcolfromdbPU
	com.sun.enterprise.util.EntityManagerFactoryWrapper.getDelegate(EntityManagerFactoryWrapper.java:159)
	com.sun.enterprise.util.EntityManagerFactoryWrapper.createEntityManager(EntityManagerFactoryWrapper.java:181)
	aaa.bbb.EntableController.getEntityManager(EntableController.java:42)
	aaa.bbb.EntableController.getItemCount(EntableController.java:175)
	aaa.bbb.EntableController.getLastItem(EntableController.java:185)
	sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	java.lang.reflect.Method.invoke(Method.java:585)
	javax.el.BeanELResolver.getValue(BeanELResolver.java:273)
	javax.el.CompositeELResolver.getValue(CompositeELResolver.java:143)
	com.sun.faces.el.FacesCompositeELResolver.getValue(FacesCompositeELResolver.java:58)
	com.sun.el.parser.AstValue.getValue(AstValue.java:117)
	com.sun.el.parser.AstDeferredExpression.getValue(AstDeferredExpression.java:46)
	com.sun.el.parser.AstCompositeExpression.getValue(AstCompositeExpression.java:51)
	com.sun.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:192)
	javax.faces.component.UIOutput.getValue(UIOutput.java:176)
	com.sun.faces.renderkit.html_basic.HtmlBasicInputRenderer.getValue(HtmlBasicInputRenderer.java:100)
	com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.getCurrentValue(HtmlBasicRenderer.java:282)
	com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeEnd(HtmlBasicRenderer.java:208)
	javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:847)
	javax.faces.component.UIComponent.encodeAll(UIComponent.java:893)
	javax.faces.render.Renderer.encodeChildren(Renderer.java:137)
	javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:827)
	javax.faces.component.UIComponent.encodeAll(UIComponent.java:883)
	javax.faces.component.UIComponent.encodeAll(UIComponent.java:889)
	com.sun.faces.application.ViewHandlerImpl.doRenderView(ViewHandlerImpl.java:258)
	com.sun.faces.application.ViewHandlerImpl.renderView(ViewHandlerImpl.java:176)
	com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:108)
	com.sun.faces.lifecycle.LifecycleImpl.phase(LifecycleImpl.java:266)
	com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:159)
	javax.faces.webapp.FacesServlet.service(FacesServlet.java:245)
	com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:73)
	com.sun.enterprise.web.VirtualServerPipeline.invoke(VirtualServerPipeline.java:120)
	org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:231)
	com.sun.enterprise.web.connector.grizzly.ProcessorTask.invokeAdapter(ProcessorTask.java:667)
	com.sun.enterprise.web.connector.grizzly.ProcessorTask.processNonBlocked(ProcessorTask.java:574)
	com.sun.enterprise.web.connector.grizzly.ProcessorTask.process(ProcessorTask.java:844)
	com.sun.enterprise.web.connector.grizzly.ReadTask.executeProcessorTask(ReadTask.java:287)
	com.sun.enterprise.web.connector.grizzly.ReadTask.doTask(ReadTask.java:212)
	com.sun.enterprise.web.connector.grizzly.TaskBase.run(TaskBase.java:252)
	com.sun.enterprise.web.connector.grizzly.WorkerThread.run(WorkerThread.java:75)