[ovirt-devel] How To Auto Set oVirt RESTApi Session？

Dear Sir： I am a new one in studing ovirt engine.Now,I have a Servlet in org.ovirt.engine.ui.frontend.server.gwt package. I want to call *Frontend.getInstance().getLoginHandler().**onLoginSuccess(userName, password, domain)* to set session for restapi in this servlet. But when I visit this servlet,it occur to show me an error which just like "*JBWEB000071: root cause java.lang.ClassNotFoundException: org.ovirt.engine.ui.uicompat.IFrontendActionAsyncCallback from [Module "deployment.engine.ear.webadmin.war:main" from Service Module Loader]*". I found that this error is occured by calling* Frontend.getInstance()*. Can you tell me how to resolve this problem or a new way to set and resume restapi session in a servlet package of org.ovirt.engine.ui.front.server.gwt like the RestApiSessionManager in org.ovirt.engine.ui.webadmin.plugin.restapi package? thanks! Best Regards!