在POST请求后重新创建ViewScoped bean时，重新执行f:viewAction [英] Re-execute f:viewAction when ViewScoped bean is recreated following a POST request

问题描述

环境:带有Mojarra 2.2.12&的JSF 2.2 CDI ViewScoped豆类javax.faces.STATE_SAVING_METHOD设置为client.

Environment: JSF 2.2 with Mojarra 2.2.12 & CDI ViewScoped beans & javax.faces.STATE_SAVING_METHOD set to client.

为了通过<f:viewParam ... />正确初始化我的bean，我想在重新创建 bean 时(重新)执行<f:viewAction action="#{bean.onLoad}" />(视图已从LRU，请参见 com.sun.faces.numberOfLogicalViews )在POST请求之后.

In order to properly initialize my bean thanks to <f:viewParam ... />, I would like to (re-)execute <f:viewAction action="#{bean.onLoad}" /> when my ViewScoped bean is recreated (view was pushed out from the LRU, cf. com.sun.faces.numberOfLogicalViews) following a POST request.

<f:metadata>
    <f:viewParam maxlength="100" name="name" value="#{bean.file}" />
    <f:viewAction action="#{bean.onLoad}"  />
</f:metadata>

<o:form includeRequestParams="true">
     <!-- action can only work if onLoad has been called -->
     <p:commandButton action="#{bean.action}" />
</o:form>

有什么想法吗?

注释:

• 我知道postBack="true"，但是它不适合在每个 POST请求中调用bean.onLoad().
• 我无法在@PostConstruct方法中调用onLoad()，因为viewParam尚未设置值(请参见

• I'm aware of postBack="true" but it's not suitable as bean.onLoad() would be called on every POST request.
• I cannot call onLoad() in @PostConstruct method because values have not been set by viewParam yet (cf. When to use f:viewAction versus PostConstruct?).

推荐答案

我知道postBack="true"，但是它不适合使用bean.onLoad()会在每个POST请求中调用.

I'm aware of postBack="true" but it's not suitable as bean.onLoad() would be called on every POST request.

您可以仅在onPostback属性中使用EL，在其中检查模型值和/或请求参数是否存在.

You can just use EL in onPostback attribute wherein you check if the model value and/or request parameter is present.

如果需要模型值，则只需检查其是否存在:

If the model value is required, then just check if it's present or not:

<f:metadata>
    <f:viewParam maxlength="100" name="name" value="#{bean.file}" required="true" />
    <f:viewAction action="#{bean.onLoad}" onPostback="#{empty bean.file}" />
</f:metadata>

如果不需要模型值，则还要检查请求参数:

If the model value is not required, then check the request parameter too:

<f:metadata>
    <f:viewParam maxlength="100" name="name" value="#{bean.file}" />
    <f:viewAction action="#{bean.onLoad}" onPostback="#{empty bean.file and not empty param.name}" />
</f:metadata>

---

我无法在@PostConstruct方法中调用onLoad()，因为viewParam尚未设置值.

I cannot call onLoad() in @PostConstruct method because values have not been set by viewParam yet.

鉴于您的代码段中存在 <o:form> ，我看到您正在使用 OmniFaces .完全相同的实用程序库提供了CDI @Param 批注，用于注入，转换和在@PostConstruct运行之前验证HTTP请求参数.

Given the presence of <o:form> in your snippet, I see that you're using OmniFaces. The very same utility library offers a CDI @Param annotation for the very purpose of injecting, converting and validating HTTP request parameters before the @PostConstruct runs.

因此，整个<f:viewParam><f:viewAction>可以按以下方式替换:

The entire <f:viewParam><f:viewAction> can therefore be replaced as below:

@Inject @Param(name="name", validators="javax.faces.Length", validatorAttributes=@Attribute(name="maximum", value="100"))
private String file;

@PostConstruct
public void onLoad() {
    if (!Faces.isValidationFailed()) {
        // ...
    }
}

或者如果您手头有Bean验证(又名JSR303):

Or if you've Bean Validation (aka JSR303) at hands:

@Inject @Param(name="name") @Size(max=100)
private String file;

@PostConstruct
public void onLoad() {
    if (!Faces.isValidationFailed()) {
        // ...
    }
}

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