现有一ArrayList，欲在页面上显示，先在后台放入sessionMap中：
ArrayList users = new ArrayList();
users.add(user1);
users.add(user2);
facesContext.getExternalContext().getSessionMap().put( "users ", users);
再在页面上显示：
<h:dataTable id= "users " value= "#{users} " var= "user " rowClasses= "oddRow, evenRow " headerClass= "tableHeader ">
<h:column>
<f:facet name= "header ">
<h:panelGroup>
<h:outputText value= "Name " /> </h:panelGroup>
</f:facet>
<h:outputText value= "#{user.displayName} " />
</h:column>
</h:dataTable>
但现在页面出不来，错误信息是：
javax.servlet.ServletException: For input string: "size "
javax.faces.webapp.FacesServlet.service(FacesServlet.java:154)
org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:264)
org.acegisecurity.intercept.web.FilterSecurityInterceptor.invoke(FilterSecurityInterceptor.java:107)
org.acegisecurity.intercept.web.FilterSecurityInterceptor.doFilter(FilterSecurityInterceptor.java:72)
org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
org.acegisecurity.ui.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:110)
org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
org.acegisecurity.ui.switchuser.SwitchUserProcessingFilter.doFilter(SwitchUserProcessingFilter.java:335)
org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
org.acegisecurity.providers.anonymous.AnonymousProcessingFilter.doFilter(AnonymousProcessingFilter.java:125)
org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
org.acegisecurity.ui.rememberme.RememberMeProcessingFilter.doFilter(RememberMeProcessingFilter.java:142)
org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
org.acegisecurity.wrapper.SecurityContextHolderAwareRequestFilter.doFilter(SecurityContextHolderAwareRequestFilter.java:81)
org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
org.acegisecurity.ui.AbstractProcessingFilter.doFilter(AbstractProcessingFilter.java:217)
org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
org.acegisecurity.context.HttpSessionContextIntegrationFilter.doFilter(HttpSessionContextIntegrationFilter.java:191)
org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
org.acegisecurity.securechannel.ChannelProcessingFilter.doFilter(ChannelProcessingFilter.java:138)
org.acegisecurity.util.FilterChainProxy$VirtualFilterChain.doFilter(FilterChainProxy.java:274)
org.acegisecurity.util.FilterChainProxy.doFilter(FilterChainProxy.java:148)
org.acegisecurity.util.FilterToBeanProxy.doFilter(FilterToBeanProxy.java:90)
org.apache.myfaces.webapp.filter.ExtensionsFilter.doFilter(ExtensionsFilter.java:147)
org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96)
root cause
java.lang.NumberFormatException: For input string: "size "