AnnotationConfiguration ac = new AnnotationConfiguration();
        try {
            File plugin = new File(Executions.getCurrent().getDesktop().getWebApp().getRealPath(Executions.getCurrent().toAbsoluteURI("/plugins/CountriesPlugin.jar", false)).toString());

            ClassLoader cl = URLClassLoader.newInstance(
                    new URL[] { new URL("jar:file://" + plugin.getAbsolutePath() + "!/") },
                    getClass().getClassLoader()
                    );

            Class<?> c = Class.forName("com.exponentum.exponentummis.plugins.CountriesPlugin.entities.Country", true, cl);
            ac.addAnnotatedClass(c);
            ac.buildMappings();
            ac.configure();
            ac.buildSessionFactory();
        } catch (Exception e) {
            e.printStackTrace();
        }

org.hibernate.MappingException: entity class not found: com.exponentum.exponentummis.plugins.CountriesPlugin.entities.Country
        at org.hibernate.mapping.PersistentClass.getMappedClass(PersistentClass.java:99)
        at org.hibernate.tuple.PropertyFactory.getGetter(PropertyFactory.java:168)
        at org.hibernate.tuple.PropertyFactory.buildIdentifierProperty(PropertyFactory.java:44)
        at org.hibernate.tuple.entity.EntityMetamodel.<init>(EntityMetamodel.java:123)
        at org.hibernate.persister.entity.AbstractEntityPersister.<init>(AbstractEntityPersister.java:434)
        at org.hibernate.persister.entity.SingleTableEntityPersister.<init>(SingleTableEntityPersister.java:109)
        at org.hibernate.persister.PersisterFactory.createClassPersister(PersisterFactory.java:55)
        at org.hibernate.impl.SessionFactoryImpl.<init>(SessionFactoryImpl.java:226)
        at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1294)
        at org.hibernate.cfg.AnnotationConfiguration.buildSessionFactory(AnnotationConfiguration.java:859)
        at com.exponentum.exponentummis.core.controller.MainController.loadPlugins(MainController.java:60)
        at com.exponentum.exponentummis.core.controller.MainController.onCreate(MainController.java:43)
        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:597)
        at org.zkoss.zk.ui.impl.EventProcessor.process0(EventProcessor.java:218)
        at org.zkoss.zk.ui.impl.EventProcessor.process(EventProcessor.java:140)
        at org.zkoss.zk.ui.impl.UiEngineImpl.processEvent(UiEngineImpl.java:1482)
        at org.zkoss.zk.ui.impl.UiEngineImpl.process(UiEngineImpl.java:1266)
        at org.zkoss.zk.ui.impl.UiEngineImpl.execNewPage0(UiEngineImpl.java:422)
        at org.zkoss.zk.ui.impl.UiEngineImpl.execNewPage(UiEngineImpl.java:291)
        at org.zkoss.zk.ui.http.DHtmlLayoutServlet.process(DHtmlLayoutServlet.java:238)
        at org.zkoss.zk.ui.http.DHtmlLayoutServlet.doGet(DHtmlLayoutServlet.java:159)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852)
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
        at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
        at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.ClassNotFoundException: com.exponentum.exponentummis.plugins.CountriesPlugin.entities.Country
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1484)
        at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1329)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:169)
        at org.hibernate.util.ReflectHelper.classForName(ReflectHelper.java:100)
        at org.hibernate.mapping.PersistentClass.getMappedClass(PersistentClass.java:96)
        ... 37 more