EL条件方法表达式 [英] EL conditional Method Expression
问题描述
我想在EL中声明一个条件方法表达式,如下所示:
I would like to declare a conditional method expression in EL like below:
<p:dataTable id="#{cc.attrs.datatableId}" var="overview"
rowSelectListener="#{cc.attrs.detailsMode == 'single' ? cc.attrs.bean.onRowSelect : cc.attrs.bean.onRowUrlSelect}">
但是,它会引发EL异常:
However, it throws an EL exception:
javax.el.ELException:不是有效的方法表达式:#{cc.attrs.detailsMode =='single'? cc.attrs.bean.onRowSelect:cc.attrs.bean.onRowUrlSelect}
javax.el.ELException: Not a Valid Method Expression: #{ cc.attrs.detailsMode == 'single' ? cc.attrs.bean.onRowSelect : cc.attrs.bean.onRowUrlSelect}
如何声明条件EL方法表达式?
How I can declare a conditional EL method expression?
推荐答案
不幸的是,方法表达式不接受值表达式.最好的选择是拥有一个方法入口点,该入口点又基于detailsMode
将其进一步委派给所需的操作方法,您也将该方法传递/设置给Bean.
Unfortunately, method expressions does not accept value expressions. Your best bet is to have a single method entry point which in turn delegates further to the desired action methods based on the detailsMode
which you also pass/set to the bean.
例如
<h:dataTable ... rowSelectListener="#{cc.attrs.bean.onRowSelect}">
public void onRowSelect(SelectEvent event) {
if ("single".equals(detailsMode)) {
onRowSingleSelect(event);
} else {
onRowUrlSelect(event);
}
}
鉴于您实际上正在使用复合组件,因此可以根据需要将其隐藏在支持组件中,以减少支持bean中的样板:
Given that you're actually using a composite component, you can if necessary hide it away in the backing component to reduce boilerplate in backing bean:
<cc:interface componentType="yourComponent">
...
<h:dataTable ... rowSelectListener="#{cc.onRowSelect}">
@FacesComponent("yourComponent")
public class YourComponent extends UINamingContainer {
public void onRowSelect(SelectEvent event) {
String methodName = "single".equals(detailsMode) ? "onRowSingleSelect" : "onRowUrlSelect";
MethodExpression method = (MethodExpression) getAttributes().get(methodName);
method.invoke(getFacesContext().getELContext(), new Object[] { event });
}
}
这篇关于EL条件方法表达式的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!