p:commandButton inside Orderlist not working - jsf

Question

I've got a question regarding Primefaces orderList.
I have an orderList which looks like this:
<p:orderList id="technikersTable"
value="#{systemlandschaftRessourceHandler.entity.technikers}"
var="_techniker"
itemValue="#{_techniker}"
converter="#{entityConverter}"
controlsLocation="none">
<f:facet name="caption">Techniker</f:facet>
<p:column>
<p:commandButton styleClass="colButton"
icon="ui-icon-trash"
action="#{systemlandschaftRessourceHandler.removeTechniker(_techniker)}"
update=":systemLandschaftTabView:sysObjektDetailPanelForm:technikersTable"/>
</p:column>
<p:column style="width:75%;">
<p:outputLabel value="#{_techniker.verantwortlich.displayName}" />
</p:column>
</p:orderList>
My problem is, that the commandButton in the first column throws a null pointer exception.
The request never reaches my bean.
Is it possible that the commandButton is not working inside the orderList?
I have done the same thing with dataTables a lot of time successfully.
StackTrace:
ERROR 2013-10-15 14:37:55,009 [MmnetExceptionHandler] Fehler auf der Seite: /views/protected/systemlandschaft/systemlandschaftHome.xhtml, isAjaxRequest=true
ERROR 2013-10-15 14:37:55,010 [MmnetExceptionHandler] [SCUE070] Allgemeiner Anwendungsfehler! : java.lang.NullPointerException
at java.lang.Class.isAssignableFrom(Native Method)
at org.apache.el.util.ReflectionUtil.isAssignableFrom(ReflectionUtil.java:319)
at org.apache.el.util.ReflectionUtil.getMethod(ReflectionUtil.java:185)
at org.apache.el.parser.AstValue.invoke(AstValue.java:257)
at org.apache.el.MethodExpressionImpl.invoke(MethodExpressionImpl.java:278)
at org.jboss.weld.util.el.ForwardingMethodExpression.invoke(ForwardingMethodExpression.java:39)
at org.jboss.weld.el.WeldMethodExpression.invoke(WeldMethodExpression.java:50)
at com.sun.faces.facelets.el.TagMethodExpression.invoke(TagMethodExpression.java:105)
at javax.faces.component.MethodBindingMethodExpressionAdapter.invoke(MethodBindingMethodExpressionAdapter.java:88)
at com.sun.faces.application.ActionListenerImpl.processAction(ActionListenerImpl.java:102)
at org.apache.myfaces.extensions.cdi.jsf.impl.security.SecurityViolationAwareActionListener.processAction(SecurityViolationAwareActionListener.java:56)
at org.apache.myfaces.extensions.cdi.jsf.impl.config.view.ViewControllerActionListener.processAction(ViewControllerActionListener.java:68)
at org.apache.myfaces.extensions.cdi.jsf.impl.listener.action.CodiActionListener.processAction(CodiActionListener.java:58)
at javax.faces.component.UICommand.broadcast(UICommand.java:315)
at javax.faces.component.UIData.broadcast(UIData.java:1093)
at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:794)
at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1259)
at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
at org.apache.myfaces.extensions.cdi.jsf2.impl.listener.phase.CodiLifecycleWrapper.execute(CodiLifecycleWrapper.java:95)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:329)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248)
at org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:79)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:280)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248)
at org.jboss.weld.servlet.ConversationPropagationFilter.doFilter(ConversationPropagationFilter.java:62)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:280)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248)
at com.ocpsoft.pretty.PrettyFilter.doFilter(PrettyFilter.java:118)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:280)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248)
at de.company.mmnet.sessioninfo.HttpSessionUserFilter.doFilter(HttpSessionUserFilter.java:42)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:280)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248)
at org.apache.catalina.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:101)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:280)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:248)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:275)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161)
at org.jboss.as.jpa.interceptor.WebNonTxEmCloserValve.invoke(WebNonTxEmCloserValve.java:50)
at org.jboss.as.web.security.SecurityContextAssociationValve.invoke(SecurityContextAssociationValve.java:165)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:372)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:877)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:679)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:931)
at java.lang.Thread.run(Thread.java:722)
DEBUG 2013-10-15 14:37:55,094 [EntityManagerProducer] EntityManager geschlossen.

Answer 1

You can use a commandbutton inside an orderList. Your problem is that you are using the #{_techniker} var as a parameter. The action property is evaluating the EL expression on serverside when you click the button, and this is causing the nullpointer.
It does indeed work in a dataTable, but the datatable component is designed differently.
I would consider using a different component, but if you really need to use the orderlist, you could use the p:remoteCommand for sending the id of the techniker to the backing bean.
Primefaces RemoteCommand

Answer 2

Expanding LStrike comment, here is the relevant content from https://forum.primefaces.org/viewtopic.php?f=3&t=34424
Bean:
#ManagedBean
#RequestScoped
public class TechnikersBean {
public List<String> getPersons() {
List<String> result = new ArrayList<String>();
result.add("Person1");
result.add("person2");
return result;
}
public void setPersons(List<String> persons) {
}
public void removeTechniker(ActionEvent event) {
Map<String, String> parameterMap = FacesContext.getCurrentInstance().getExternalContext()
.getRequestParameterMap();
String name = parameterMap.get("name");
System.out.println(name);
}
}
xhtml:
<h:form id="form">
<p:remoteCommand name="removeTechniker" actionListener="#{technikersBean.removeTechniker}"
out="technikersTable" />
<p:orderList id="technikersTable"
value="#{technikersBean.persons}"
var="_techniker"
itemValue="#{_techniker}"
controlsLocation="none">
<f:facet name="caption">Techniker</f:facet>
<p:column>
<p:commandButton styleClass="colButton"
icon="ui-icon-trash"
type="button" onclick="removeTechniker([{name:'name', value:'#{_techniker}'}]);">
</p:commandButton>
</p:column>
<p:column style="width:75%;">
<p:outputLabel value="#{_techniker}"/>
</p:column>
</p:orderList>
</h:form>
Basically, a remoteComand is called by a client side callback to send the required information to the bean function.