Conflict about required and valuechangeListener for <p:selectonemenu>

问题

<p:selectOneMenu id="roleId" value="#{accessPage.roleId}" required="true">                   
   <f:selectItem itemLabel="#{msg['label.common.selecthere']}" itemValue="#{null}" />          
   <f:selectItems var="code" value="#{accessPage.roleIdList}" itemLabel="#{code.codeDesc}" itemValue="#{code.codeId}" />    
   <f:valueChangeListener type="com.ncs.caseconnect.base.app.utils.ValueChangeCleanUtils"/>    
   <p:ajax listener="#{accessPage.roleOrModuleChanged}" update="accessRight" />
</p:selectOneMenu>

the valueChangeListener and ajax not work when we select the first null option. If we remove the required attribute it works fine. Is it conflict between required and valueChangeListener?

回答1:

try to replace

<f:selectItem itemLabel="#{msg['label.common.selecthere']}" itemValue="#{null}" />  

with

<f:selectItem noSelectionOption="true" itemLabel="#{msg['label.common.selecthere']}"/>

来源：https://stackoverflow.com/questions/11027275/conflict-about-required-and-valuechangelistener-for-pselectonemenu