我正在研究j2ee web应用程序（jsf2和primefaces），我想知道如何根据从选择一个菜单中选择的项目来显示表单。 我尝试了这个，但它没有用。
<h:form id="global">
<p:panel header="Association">
...
<p:outputLabel value="Travel Class" />
<p:selectOneMenu id="associationType" style="width: 230px" value="#{associationMBean.travelClass}">
<f:selectItem itemLabel="Select one" itemValue="" />
<f:selectItem itemLabel="Seminar" itemValue="Seminar" />
<f:selectItem itemLabel="Honeymoon" itemValue="Honeymoon" />
<f:selectItem itemLabel="Organized Trip" itemValue="Organized Trip" />
<p:ajax update=":hidePanel"/>
</p:selectOneMenu>
</p:panel>
</h:form>
<p:panel id="hidePanel" style="margin-top: 20px; font-size: 14px; border: 0;display: none " header="Remarks (Optional)" rendered="#{associationMBean.travelClass eq Seminar}">
<h:form>
<p:inputTextarea style="width: 100% ; height: 100px" value="#{associationMBean.description}" ></p:inputTextarea>
</h:form>
</p:panel>
更新
<html
xmlns:f="http://java.sun.com/jsf/core"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:p="http://primefaces.org/ui">
<h:head>
<title>Visa Application-Thailand</title>
</h:head>
<h:body>
<div align="center">
<div>
<img class="logo" src="images/banner.jpg"/>
</div>
<p:panel style="width: 61%; border-color: indianred; border-width: 2px; margin-top: 10px">
<h:form id="global">
<p:panel style="margin-top: 20px; font-size: 14px ; border: 0" header="Association">
<table border="0" >
<tbody >
<tr>
<td align="right">
<p:outputLabel value="Association Type" />
</td >
<td align="left">
<p:selectOneMenu id="selectmenu" style="width: 230px" value="#{associationMBean.type}">
<f:selectItem itemLabel="Select a Class" itemValue="" />
<f:selectItem itemLabel="Seminar" itemValue="Seminar" />
<f:selectItem itemLabel="Organized Trip" itemValue="Organized Trip" />
<f:selectItem itemLabel="Honeymoon" itemValue="Honeymoon" />
<p:ajax update=":hidePanel"/>
</p:selectOneMenu>
</td>
</tr>
<tr>
<td align="right">
<p:outputLabel value="Date of Departure" for="departure" />
</td>
<td align="left">
<p:calendar value="#{associationMBean.departure}" showOn="button" pattern="dd/MM/yy" style="width: 250px" id="departure"></p:calendar>
<p:watermark value="01/01/2014" for="departure"/>
</td>
</tr>
<tr>
<td align="right">
<p:outputLabel value="Date of Arrival" for="arrival" />
</td>
<td align="left">
<p:calendar value="#{associationMBean.arrival}" showOn="button" pattern="dd/MM/yy" style="width: 250px" id="arrival"></p:calendar>
<p:watermark value="01/01/2014" for="arrival"/>
</td>
</tr>
<tr>
<td align="right">
<p:outputLabel value="Travel Agency " for="travelAgency"/>
</td>
<td align="left">
<p:inputText id="travelAgency" value="#{associationMBean.travelAgency}" style="width: 220px"></p:inputText>
</td>
</tr>
<tr>
<td align="right">
<p:outputLabel value="Airline " for="airline"/>
</td>
<td align="left">
<p:inputText id="airline" value="#{associationMBean.airline}" style="width: 220px"></p:inputText>
</td>
</tr>
<tr>
<td align="right">
<p:outputLabel value="Travel Class" />
</td >
<td align="left">
<p:selectOneMenu id="selectclass" style="width: 230px" value="#{associationMBean.travelClass}">
<f:selectItem itemLabel="Select a Class" itemValue="" />
<f:selectItems value="#{associationMBean.allClasses}" />
<!-- <p:ajax update=":hidePanel"/> !-->
</p:selectOneMenu>
</td>
</tr>
<tr >
<td align="right">
<p:outputLabel value="Hotels " for="hotels" />
</td>
<td align="left">
<p:inputTextarea id="hotels" value="#{associationMBean.hotels}" style="width: 220px"/>
</td>
</tr>
</tbody>
</table>
</p:panel>
<div align="right" style="margin-top: 20px ">
<p:commandButton type="reset" value="Reset" style="font-size: 14px;"/>
<p:commandButton value="Save" ajax="false" styleClass="ui-priority-primary" style="font-size: 14px;" action="#{associationMBean.addAssociation()}" />
</div>
</h:form>
<p:panel id="hidePanel" style="margin-top: 20px; font-size: 14px; border: 0;display: none " header="Remarks (Optional)" >
<h:form rendered="#{associationMBean.type == 'Seminar'}" >
<p:inputTextarea style="width: 100% ; height: 100px" value="#{visaMBean.description}" ></p:inputTextarea>
</h:form>
</p:panel>
</p:panel>
</div>
</h:body>
</html>
上面的代码是添加一些更新后的整个html代码<h:form rendered="#{associationMBean.type == 'Seminar'}" >但是当我从selectOneMenu中选择Seminar时仍然无法显示hidePane。
你知道我错过了什么吗？
答案 0 :(得分：1)
以下内容应该有效：
<p:panel id="hidePanel" style="margin-top: 20px; font-size: 14px; border: 0;display: none " header="Remarks (Optional)">
<h:form rendered="#{associationMBean.travelClass eq 'Seminar'}">
<p:inputTextarea style="width: 100% ; height: 100px" value="#{associationMBean.description}" ></p:inputTextarea>
</h:form>
</p:panel>
您无法更新不在DOM中的组件，并且当组件未呈现时，它不在那里。因此，您需要更新有条件渲染的组件的父级。
由于#{associationMBean.travelClass}是一个字符串，您需要使用单引号'Seminar'包裹'。