如何在JSF组件的on *属性中调用托管bean动作方法 [英] How to invoke a managed bean action method in on* attribute of a JSF component

问题描述

我想在on*属性中调用托管bean操作方法.在我的特殊情况下，如果用户闲置3分钟，则需要注销该用户，如下所示:

I'd like to invoke a managed bean action method in an on* attribute. In my particular case I need to logout an user if the user is idle for 3 minutes as below:

<p:idleMonitor onidle="#{mybean.processTimeOut()}" timeout="180000" /> 

但是，托管的bean动作方法会在页面加载时立即被调用.这是怎么引起的，我该如何解决?

However, the managed bean action method is immediately invoked as the page loads. How is this caused and how can I solve it?

推荐答案

与所有JSF组件上的所有其他on*属性一样， onidle属性必须表示JavaScript回调，而不是JSF支持bean操作方法. on*属性中的任何EL表达式在生成HTML输出时都将被立即评估为String值表达式，以期望它们打印(部分)JavaScript代码.

Like as all other on* attributes on all JSF components, the onidle attribute must represent a JavaScript callback, not a JSF backing bean action method. Any EL expressions in on* attributes would be evaluated immediately as String value expressions during generating the HTML output in expectation that they print (part of) JavaScript code.

这就像您正在执行<h:outputText value="#{mybean.processTimeout()}">一样.如果您删除了括号()，则会遇到PropertyNotFoundException，这也暗示了它被评估为值表达式而不是方法表达式.

It's exactly like as if you're doing <h:outputText value="#{mybean.processTimeout()}">. If you had removed the parentheses (), you'd have faced a PropertyNotFoundException which was also a hint at its own of it being evaluated as a value expression instead of a method expression.

为了使用JavaScript调用JSF支持bean方法，您需要一个附加的 <p:remoteCommand> .

In order to invoke a JSF backing bean method using JavaScript, you need an additional <p:remoteCommand>.

<p:idleMonitor onidle="processTimeout()" timeout="180000" /> 
<p:remoteCommand name="processTimeout" action="#{mybean.processTimeOut}" />

如果您不在PrimeFaces上，请转到此相关答案中发布的替代方法:

If you're not on PrimeFaces, head to the alternatives posted in this related answer: How to invoke a JSF managed bean on a HTML DOM event using native JavaScript?

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