jsf-2 - 如何使视图参数在@RequestScoped bean 的视图中包含的表单引起的任何验证失败中幸存下来？

Question

索引.xhtml：

    <f:metadata>
        <f:viewParam id="playernameparam" name="playernameparam" required="true" 
                requiredMessage="Player name required!" 
                value="#{playersBean.playerName}"/>            
        <f:viewParam id="playersurnameparam" name="playersurnameparam" required="true" 
                requiredMessage="Player surname required!" 
                value="#{playersBean.playerSurname}"/> 
    </f:metadata>
    <h:message for="playernameparam" />
    <h:message for="playersurnameparam" />
    <h:head>
        <title></title>
    </h:head>   
    <h:body>        
        <h:form>
            Enter name:<h:inputText value="#{playersBean.playerName}"/><br/>
            Enter surname:<h:inputText value="#{playersBean.playerSurname}"/><br/>
            For validation purpose: <h:inputText id="address" 
                    value="#{playersBean.address}" required="true" 
                    requiredMessage="Kindly fill your address location" /><br/>
            <h:message for="address" style="color:red" /><br/>
            <h:commandButton value="Submit" action="#{playersBean.action()}">
            </h:commandButton>
        </h:form>       
    </h:body>

结果.xhtml：

    <f:metadata>
        <f:viewParam name="playernameparam" value="#{playersBean.playerName}"/>            
        <f:viewParam name="playersurnameparam" value="#{playersBean.playerSurname}"/> 
    </f:metadata>
    <h:head>
        <title></title>
    </h:head>   
    <h:body>        
        You requested name: <h:outputText value="#{playersBean.playerName}"/><br/>
        You requested surname: <h:outputText value="#{playersBean.playerSurname}"/>       
    </h:body>

托管豆：

@ViewScoped
@ManagedBean(name = "playersBean")
public class PlayersBean implements Serializable {

    private String playerName;
    private String playerSurname;
    private String address;
    // getters & setters

    public String action() {
        return "results?faces-redirect=true&includeViewParams=true";
    }
}

击球时http://localhost:8080/Leonard/faces/ch2/index.xhtml?playernameparam=FARHAN&playersurnameparam=ANSARI

将“验证目的”字段留空以触发验证失败

然后按下按钮。

现在在同一字段中输入一些内容，然后再次按 Enter。

它工作得很好，视图参数在那里，重定向的 url 反映为：

http://localhost:8080/Leonard/faces/ch2/results.xhtml?playernameparam=FARHAN&playersurnameparam=ANSARI

当然它会像豆子一样@ViewScoped。

但是我的 bean 是 @RequestScoped，这导致了问题。我在验证失败时丢失了它们，然后在使用 POST 请求删除验证错误后进行后续 POST，从而产生以下结果：

那么，问题归结为如何保留请求参数？