After following the steps in http://www.ovirt.org/Building_oVirt_engine, I met some problems in deploying it.
Here's  the status while I visit http://localhost:8700/webadmin/webadmin/WebAdmin.html

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: Servlet execution threw an exception
	org.ovirt.engine.ui.frontend.server.gwt.GwtCachingFilter.doFilter(GwtCachingFilter.java:132)

root cause 

java.lang.NoClassDefFoundError: Could not initialize class org.ovirt.engine.ui.frontend.server.gwt.plugin.PluginDataManager$Holder
	org.ovirt.engine.ui.frontend.server.gwt.plugin.PluginDataManager.getInstance(PluginDataManager.java:74)
	org.ovirt.engine.ui.frontend.server.gwt.WebAdminHostPageServlet.getPluginData(WebAdminHostPageServlet.java:85)
	org.ovirt.engine.ui.frontend.server.gwt.WebAdminHostPageServlet.doGet(WebAdminHostPageServlet.java:53)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:734)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:847)
	org.ovirt.engine.ui.frontend.server.gwt.GwtCachingFilter.doFilter(GwtCachingFilter.java:132)

note The full stack trace of the root cause is available in the JBoss Web/7.0.13.Final logs.

JBoss Web/7.0.13.Final



What does it mean? And What should I do next?
Thanks!!