JSF新手请教分页问题，先谢过各位了^_^

Question

下面是JBoss报的错
16:34:05,450 INFO  [STDOUT] 16:34:05,450 ERROR [CommandLinkRenderer] component scroll_1first must be enclosed inside a form 
16:34:05,450 INFO  [STDOUT] 16:34:05,450 ERROR [[jsp]] Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
        at com.sun.faces.renderkit.html_basic.CommandLinkRenderer.getHiddenFieldName(CommandLinkRenderer.java:136)
        at com.sun.faces.renderkit.html_basic.CommandLinkRenderer.encodeEnd(CommandLinkRenderer.java:320)
        at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:712)
        at org.apache.myfaces.custom.datascroller.HtmlDataScrollerRenderer.renderFacet(HtmlDataScrollerRenderer.java:294)
        at org.apache.myfaces.custom.datascroller.HtmlDataScrollerRenderer.renderScroller(HtmlDataScrollerRenderer.java:236)
        at org.apache.myfaces.custom.datascroller.HtmlDataScrollerRenderer.encodeEnd(HtmlDataScrollerRenderer.java:207)
        at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:712)
        at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:443)
        at com.sun.faces.renderkit.html_basic.GridRenderer.encodeChildren(GridRenderer.java:233)
        at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:693)
        at javax.faces.webapp.UIComponentTag.encodeChildren(UIComponentTag.java:600)
        at javax.faces.webapp.UIComponentTag.doEndTag(UIComponentTag.java:537)
        at com.sun.faces.taglib.html_basic.PanelGridTag.doEndTag(PanelGridTag.java:460)
        at org.apache.jsp.studentmanage.userlist_jsp._jspx_meth_h_panelGrid_0(userlist_jsp.java:599)
        at org.apache.jsp.studentmanage.userlist_jsp._jspx_meth_f_view_0(userlist_jsp.java:169)
        at org.apache.jsp.studentmanage.userlist_jsp._jspService(userlist_jsp.java:127)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:334)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
        at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:672)
        at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:463)
        at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:398)
        at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:301)
        at com.sun.faces.context.ExternalContextImpl.dispatch(ExternalContextImpl.java:322)
        at com.sun.faces.application.ViewHandlerImpl.renderView(ViewHandlerImpl.java:147)
        at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:87)
        at com.sun.faces.lifecycle.LifecycleImpl.phase(LifecycleImpl.java:200)
        at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:117)
        at javax.faces.webapp.FacesServlet.service(FacesServlet.java:198)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
        at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
        at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:175)
        at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:74)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
        at org.jboss.web.tomcat.tc5.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:156)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
        at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664)
        at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
        at org.apache.tomcat.util.net.MasterSlaveWorkerThread.run(MasterSlaveWorkerThread.java:112)
        at java.lang.Thread.run(Thread.java:595)

Answer 1

16:34:05,450 INFO  [STDOUT] 16:34:05,450 ERROR [[Faces Servlet]] Servlet.service() for servlet Faces Servlet threw exception
java.lang.NullPointerException
        at com.sun.faces.renderkit.html_basic.CommandLinkRenderer.getHiddenFieldName(CommandLinkRenderer.java:136)
        at com.sun.faces.renderkit.html_basic.CommandLinkRenderer.encodeEnd(CommandLinkRenderer.java:320)
        at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:712)
        at org.apache.myfaces.custom.datascroller.HtmlDataScrollerRenderer.renderFacet(HtmlDataScrollerRenderer.java:294)
        at org.apache.myfaces.custom.datascroller.HtmlDataScrollerRenderer.renderScroller(HtmlDataScrollerRenderer.java:236)
        at org.apache.myfaces.custom.datascroller.HtmlDataScrollerRenderer.encodeEnd(HtmlDataScrollerRenderer.java:207)
        at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:712)
        at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:443)
        at com.sun.faces.renderkit.html_basic.GridRenderer.encodeChildren(GridRenderer.java:233)
        at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:693)
        at javax.faces.webapp.UIComponentTag.encodeChildren(UIComponentTag.java:600)
        at javax.faces.webapp.UIComponentTag.doEndTag(UIComponentTag.java:537)
        at com.sun.faces.taglib.html_basic.PanelGridTag.doEndTag(PanelGridTag.java:460)
        at org.apache.jsp.studentmanage.userlist_jsp._jspx_meth_h_panelGrid_0(userlist_jsp.java:599)
        at org.apache.jsp.studentmanage.userlist_jsp._jspx_meth_f_view_0(userlist_jsp.java:169)
        at org.apache.jsp.studentmanage.userlist_jsp._jspService(userlist_jsp.java:127)
        at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
        at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:334)
        at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:314)
        at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:264)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
        at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:672)
        at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:463)
        at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:398)
        at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:301)
        at com.sun.faces.context.ExternalContextImpl.dispatch(ExternalContextImpl.java:322)
        at com.sun.faces.application.ViewHandlerImpl.renderView(ViewHandlerImpl.java:147)
        at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:87)
        at com.sun.faces.lifecycle.LifecycleImpl.phase(LifecycleImpl.java:200)
        at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:117)
        at javax.faces.webapp.FacesServlet.service(FacesServlet.java:198)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
        at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
        at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:175)
        at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:74)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
        at org.jboss.web.tomcat.tc5.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:156)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:869)
        at org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:664)
        at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
        at org.apache.tomcat.util.net.MasterSlaveWorkerThread.run(MasterSlaveWorkerThread.java:112)
        at java.lang.Thread.run(Thread.java:595)

Answer 2

dataScroller的scroll_1是什么，那里有个空指针(NullPointerException)错