BalusC像往常一样给出了很好的答案！

Great answer from BalusC as usual!

我只想添加，当我使用他的代码设置keepMessages属性时，它没有为会话设置，而是仅针对此请求（尽管它在Javadocs中说的是什么）。

I just want to add, when i used his code to set the keepMessages property, it was not set for the session, but only for this request (despite what it says in the Javadocs).

我将以下代码放入header.xhtml
< c：set target =＃{flash}property =keepMessagesvalue =true/>

I put the following code in my header.xhtml <c:set target="#{flash}" property="keepMessages" value="true" />

现在它适用于每一页，我不必每次在背景中都需要它豆。
你需要JSTL，不要忘记将以下内容放在你的xhtml标题中：
xmlns：c =http://java.sun.com/jsp/jstl/核心

Now it works on every page, without me having to set it every time i need it in the backing bean. You need JSTL for this and dont forget to put the following in your xhtml header: xmlns:c="http://java.sun.com/jsp/jstl/core"