有没有一种方法可以以编程方式检测用户何时在浏览器中按F5按钮? [英] Is there a way to programatically detect when the user presses F5 button in browser?

问题描述

我有一个缓存，当用户在浏览器中发出F5请求时，我想使该缓存失效.我正在运行JSF 2.0应用程序.有办法吗?

I have a cache that I would like to invalidate whenever user issues a F5 request in the browser. I am running a JSF 2.0 application. Is there a way to do this?

推荐答案

使用

Use the FacesContext.getCurrentInstance().isPostBack() to check whether a page request is a reload of the same page. An ideal spot for this would be in a <f:viewAction/> ( new with JSF-2.2) or preRenderView event.

1. 定义backing bean方法

1. Define the backing bean method

public static boolean isPostback() {
   return FacesContext.getCurrentInstance().isPostback();
} 

使用其中一个

Use either

• <f:viewAction/>

<f:metadata>
     <f:viewAction action="#{bean.isPostBack}" onPostBack="true"/>
</f:metadata>

f:event

<f:metadata>
     <f:event type="preRenderView" listener="#{bean.isPostBack}"/>
</f:metadata>

---

OR

您可以完全跳过整个后备豆isPostBack的检查，直接在页面上直接执行缓存清除方法.

You could skip the whole backing bean isPostBack check altogether and directly execute the cache-clearing method directly from the page.

• <f:viewAction/>

    <f:metadata>
         <f:viewAction action="#{bean.clearCache}" rendered="#{facesContext.postBack}" onPostBack="true"/>
    </f:metadata>

f:event

    <f:metadata>
         <f:event type="preRenderView" rendered="#{facesContext.postBack}" listener="#{bean.clearCache}"/>
    </f:metadata>

此方法的好处是您编写的代码更少，并且当请求为回发请求时，缓存清除机制仍仅执行

The benefit with this approach is that you write less code, and your cache clearing mechanism still executes only when the request is a post back

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