刚开始学习JSF，碰到这么一个问题，求救大神！！！

java.lang.NullPointerException
?? ?at javax.faces.webapp.UIComponentClassicTagBase.setJspId(UIComponentClassicTagBase.java:1856)
?? ?at org.apache.jsp.index_jsp._jspx_meth_f_005fview_005f0(index_jsp.java:144)
?? ?at org.apache.jsp.index_jsp._jspService(index_jsp.java:116)
?? ?at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
?? ?at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
?? ?at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
?? ?at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:403)
?? ?at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:347)
?? ?at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
?? ?at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
?? ?at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
?? ?at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
?? ?at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
?? ?at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
?? ?at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:221)
?? ?at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:107)
?? ?at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
?? ?at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155)
?? ?at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:76)
?? ?at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:934)
?? ?at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:90)
?? ?at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:515)
?? ?at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1012)
?? ?at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:642)
?? ?at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:282)
?? ?at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2461)
?? ?at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2450)
?? ?at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
?? ?at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
?? ?at java.lang.Thread.run(Thread.java:744)

?