我有一个非常基本的页面，其中包含DataTable和CommandButton：
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:p="http://primefaces.org/ui">
<h:head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
</h:head>
<h:body>
<p:dataTable id="npeTestTable"
var="_element" value="#{testBB.listOfElements}"
draggableColumns="true" >
<p:column headerText="Column one">
<h:outputText value="#{_element}" />
</p:column>
</p:dataTable>
<h:form>
<p:commandButton value="Click me" />
</h:form>
</h:body>
</html>
方法testBB.getListOfElements()只返回Integer - 值的集合。
重要的是，DataTable设置了属性draggableColumns="true"。如果我单击CommandButton，我会得到以下NullPointerException：
09:59:04,018 SCHWERWIEGEND [org.primefaces.extensions.component.ajaxerrorhandler.AjaxExceptionHandler] (http-0.0.0.0-0.0.0.0-8080-6) null: javax.faces.FacesException
at com.sun.faces.lifecycle.ApplyRequestValuesPhase.execute(ApplyRequestValuesPhase.java:86) [jsf-impl-2.1.7-jbossorg-2.jar:]
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) [jsf-impl-2.1.7-jbossorg-2.jar:]
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118) [jsf-impl-2.1.7-jbossorg-2.jar:]
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:329) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248) [jbossweb-7.0.13.Final.jar:]
at org.jboss.weld.servlet.ConversationPropagationFilter.doFilter(ConversationPropagationFilter.java:62) [weld-core-1.1.16.Final.jar:2013-09-23 14:44]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:280) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248) [jbossweb-7.0.13.Final.jar:]
at org.omnifaces.filter.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:115) [omnifaces-1.6.3.jar:1.6.3]
at org.omnifaces.filter.HttpFilter.doFilter(HttpFilter.java:75) [omnifaces-1.6.3.jar:1.6.3]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:280) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248) [jbossweb-7.0.13.Final.jar:]
at org.apache.shiro.web.servlet.AbstractShiroFilter.executeChain(AbstractShiroFilter.java:449) [shiro-web-1.2.2.jar:1.2.2]
at org.apache.shiro.web.servlet.AbstractShiroFilter$1.call(AbstractShiroFilter.java:365) [shiro-web-1.2.2.jar:1.2.2]
at org.apache.shiro.subject.support.SubjectCallable.doCall(SubjectCallable.java:90) [shiro-core-1.2.2.jar:1.2.2]
at org.apache.shiro.subject.support.SubjectCallable.call(SubjectCallable.java:83) [shiro-core-1.2.2.jar:1.2.2]
at org.apache.shiro.subject.support.DelegatingSubject.execute(DelegatingSubject.java:383) [shiro-core-1.2.2.jar:1.2.2]
at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:362) [shiro-web-1.2.2.jar:1.2.2]
at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125) [shiro-web-1.2.2.jar:1.2.2]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:280) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:275) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:397) [jbossweb-7.0.13.Final.jar:]
at org.jboss.as.jpa.interceptor.WebNonTxEmCloserValve.invoke(WebNonTxEmCloserValve.java:50) [jboss-as-jpa-7.1.1.Final.jar:7.1.1.Final]
at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:153) [jboss-as-web-7.1.1.Final.jar:7.1.1.Final]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) [jbossweb-7.0.13.Final.jar:]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:368) [jbossweb-7.0.13.Final.jar:]
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:877) [jbossweb-7.0.13.Final.jar:]
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:671) [jbossweb-7.0.13.Final.jar:]
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:930) [jbossweb-7.0.13.Final.jar:]
at java.lang.Thread.run(Thread.java:662) [rt.jar:1.6.0_33]
Caused by: java.lang.NullPointerException
at org.primefaces.component.datatable.feature.DraggableColumnsFeature.decode(DraggableColumnsFeature.java:35) [primefaces-4.0.jar:4.0]
at org.primefaces.component.datatable.DataTableRenderer.decode(DataTableRenderer.java:60) [primefaces-4.0.jar:4.0]
at javax.faces.component.UIComponentBase.decode(UIComponentBase.java:787) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
at org.primefaces.component.api.UIData.processDecodes(UIData.java:232) [primefaces-4.0.jar:4.0]
at javax.faces.component.UIComponentBase.processDecodes(UIComponentBase.java:1176) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
at javax.faces.component.UIComponentBase.processDecodes(UIComponentBase.java:1176) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
at javax.faces.component.UIViewRoot.processDecodes(UIViewRoot.java:933) [jboss-jsf-api_2.1_spec-2.0.1.Final.jar:2.0.1.Final]
at com.sun.faces.lifecycle.ApplyRequestValuesPhase.execute(ApplyRequestValuesPhase.java:78) [jsf-impl-2.1.7-jbossorg-2.jar:]
... 34 more
DraggableColumnsFeature想要获取request-parameter的columnOrder，但它不在。调用split会引发异常。
对我来说，这似乎是一个Primefaces-bug。由于该示例看起来很基本，我无法相信到目前为止还没有检测到这个问题。所以我不确定我是否错过了重要的事情或概念（这基本上是我想问的问题）。
我正在运行Primefaces 4.0，Mojarra 2.1.7-jbossorg-1，JBoss 7.1.1。