After letting RHQ rest for a while, the session expires, and when AJAX components send requests, NPE occurs. Generally, this scenario is not well handled. This is one of it's symptoms. 2011-03-15 17:47:23,058 ERROR [org.rhq.enterprise.gui.common.error.GenericErrorUIBean] Error processing user request java.lang.NullPointerException at java.lang.String.compareTo(String.java:1167) at java.lang.String.compareTo(String.java:92) at java.util.Arrays.mergeSort(Arrays.java:1144) at java.util.Arrays.sort(Arrays.java:1079) at com.sun.faces.renderkit.RenderKitUtils.renderPassThruAttributesOptimized(RenderKitUtils.java:529) at com.sun.faces.renderkit.RenderKitUtils.renderPassThruAttributes(RenderKitUtils.java:365) at com.sun.faces.renderkit.html_basic.TextRenderer.getEndTextToRender(TextRenderer.java:145) at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeEnd(HtmlBasicRenderer.java:160) at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:861) at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:244) at com.sun.faces.renderkit.html_basic.GroupRenderer.encodeChildren(GroupRenderer.java:106) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:277) at org.ajax4jsf.renderkit.RendererBase.renderChildren(RendererBase.java:258) at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:279) at org.richfaces.renderkit.AbstractRowsRenderer.encodeCellChildren(AbstractRowsRenderer.java:288) at org.richfaces.renderkit.html.ColgroupRenderer.encodeChildren(ColgroupRenderer.java:98) at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:837) at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:277) at org.richfaces.renderkit.AbstractRowsRenderer.encodeCellChildren(AbstractRowsRenderer.java:288) at org.richfaces.renderkit.AbstractRowsRenderer.encodeTableHeaderFacet(AbstractRowsRenderer.java:312) at org.richfaces.renderkit.AbstractTableRenderer.encodeFooter(AbstractTableRenderer.java:335) at org.richfaces.renderkit.AbstractTableRenderer.encodeTableStructure(AbstractTableRenderer.java:160) at org.richfaces.renderkit.html.DataTableRenderer.doEncodeBegin(DataTableRenderer.java:140) at org.richfaces.renderkit.html.DataTableRenderer.doEncodeBegin(DataTableRenderer.java:128) at org.ajax4jsf.renderkit.RendererBase.encodeBegin(RendererBase.java:100) at javax.faces.component.UIComponentBase.encodeBegin(UIComponentBase.java:813) at javax.faces.component.UIData.encodeBegin(UIData.java:983) at org.ajax4jsf.component.UIDataAdaptorBase.encodeBegin(UIDataAdaptorBase.java:1225) at org.ajax4jsf.renderkit.RendererBase.renderChild(RendererBase.java:275) at org.ajax4jsf.renderkit.AjaxChildrenRenderer.encodeAjaxComponent(AjaxChildrenRenderer.java:166) at org.ajax4jsf.renderkit.AjaxChildrenRenderer.encodeAjaxChildren(AjaxChildrenRenderer.java:83) at org.ajax4jsf.renderkit.AjaxChildrenRenderer.encodeAjaxComponent(AjaxChildrenRenderer.java:157) at org.ajax4jsf.renderkit.AjaxChildrenRenderer.encodeAjaxChildren(AjaxChildrenRenderer.java:83) at org.ajax4jsf.renderkit.AjaxChildrenRenderer.encodeAjaxComponent(AjaxChildrenRenderer.java:157) at org.ajax4jsf.renderkit.AjaxChildrenRenderer.encodeAjaxChildren(AjaxChildrenRenderer.java:83) at org.ajax4jsf.renderkit.AjaxChildrenRenderer.encodeAjaxComponent(AjaxChildrenRenderer.java:157) at org.ajax4jsf.renderkit.AjaxChildrenRenderer.encodeAjaxChildren(AjaxChildrenRenderer.java:83) at org.ajax4jsf.renderkit.AjaxChildrenRenderer.encodeAjaxComponent(AjaxChildrenRenderer.java:157) at org.ajax4jsf.renderkit.AjaxContainerRenderer.encodeAjax(AjaxContainerRenderer.java:124) at org.ajax4jsf.component.AjaxViewRoot.encodeAjax(AjaxViewRoot.java:685) at org.ajax4jsf.component.AjaxViewRoot.encodeChildren(AjaxViewRoot.java:556) at javax.faces.component.UIComponent.encodeAll(UIComponent.java:930) at com.sun.facelets.FaceletViewHandler.renderView(FaceletViewHandler.java:592) at org.rhq.enterprise.gui.common.framework.FaceletRedirectionViewHandler.renderView(FaceletRedirectionViewHandler.java:64) at org.ajax4jsf.application.ViewHandlerWrapper.renderView(ViewHandlerWrapper.java:100) at org.ajax4jsf.application.AjaxViewHandler.renderView(AjaxViewHandler.java:176) at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:110) at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:100) at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139) at javax.faces.webapp.FacesServlet.service(FacesServlet.java:266) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:530) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.rhq.enterprise.gui.legacy.WebUserTrackingFilter.doFilter(WebUserTrackingFilter.java:50) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.rhq.enterprise.gui.legacy.AuthenticationFilter.doFilter(AuthenticationFilter.java:129) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.rhq.enterprise.gui.common.upload.MultipartFilter.doFilter(MultipartFilter.java:63) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:83) at org.jboss.seam.web.IdentityFilter.doFilter(IdentityFilter.java:40) at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69) at org.jboss.seam.web.MultipartFilter.doFilter(MultipartFilter.java:90) at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69) at org.jboss.seam.web.ExceptionFilter.doFilter(ExceptionFilter.java:64) at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69) at org.jboss.seam.web.RedirectFilter.doFilter(RedirectFilter.java:45) at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69) at org.ajax4jsf.webapp.BaseXMLFilter.doXmlFilter(BaseXMLFilter.java:206) at org.ajax4jsf.webapp.BaseFilter.handleRequest(BaseFilter.java:290) at org.ajax4jsf.webapp.BaseFilter.processUploadsAndHandleRequest(BaseFilter.java:388) at org.ajax4jsf.webapp.BaseFilter.doFilter(BaseFilter.java:515) at org.jboss.seam.web.Ajax4jsfFilter.doFilter(Ajax4jsfFilter.java:56) at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69) at org.jboss.seam.web.LoggingFilter.doFilter(LoggingFilter.java:60) at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69) at org.jboss.seam.web.HotDeployFilter.doFilter(HotDeployFilter.java:53) at org.jboss.seam.servlet.SeamFilter$FilterChainImpl.doFilter(SeamFilter.java:69) at org.jboss.seam.servlet.SeamFilter.doFilter(SeamFilter.java:158) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.rhq.helpers.rtfilter.filter.RtFilter.doFilter(RtFilter.java:124) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:173) at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:182) at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:104) at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:157) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:241) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447) at java.lang.Thread.run(Thread.java:662)