p：commandButton onclick中的EL表达式不会在ajax请求上更新/重新呈现？ [英] EL expression inside p:commandButton onclick does not update/re-render on ajax request?

问题描述

我的 commandButton 的 onclick 属性里面有一些EL依赖的Javascript。更具体地说，这是一段代码：

The onclick attribute of my commandButton has some EL dependent Javascript inside. To be more specific, here is that piece of code:

<p:commandButton
    onclick="javascript: if('#{userBean.user.friendList.size() gt 0}' == 'true') deleteFriendsConfirmDialog.show(); else friendsAlreadyDeletedErrorDialog.show();"
    value="Delete all friends?" />

deleteFriendsConfirmDialog 清除朋友和更新列表 @form 。朋友列表，commandButton和对话都是这种形式。

deleteFriendsConfirmDialog clears the list of friends and updates the @form. The list of friends, commandButton and the dialogs are all in that form.

所以我点击按钮，出现确认对话框（因为朋友列表的长度是gt 0），我确认清单清空，视图更新。但是，当我再次单击删除所有朋友？按钮时，将再次出现确认对话框。由于列表的长度现在为0，我反而希望显示错误对话框。

So I click the button, confirmation dialog comes up (because the length of friends' list is gt 0), I confirm and the list is emptied, the view is updated. However, when I click the Delete all friends? button once more, the confirmation dialog comes up again. Since the length of the list is now 0, I instead expect the error dialog to show.

我想，这是因为写在 onclick 未更新（虽然按钮位于表单中）。

That, I guess, is because the Javascript written inside onclick is not updated (although the button is in the form).

修改：更改＃{userBean.user.friendList.size（）gt 0} to ＃{not empty userBean.user.friendList} doesn'不工作。

Changing #{userBean.user.friendList.size() gt 0} to #{not empty userBean.user.friendList} doesn't work neither.

为什么？这里有什么问题？

How come? What's wrong here?

任何帮助表示赞赏。 ：）

Any help appreciated. :)

推荐答案

确实如此。 PrimeFaces（和标准JSF）不会在每个请求的基础上重新评估* 属性上的中的EL。它只发生在每个视图的基础上。然而，RichFaces在< a4j：xxx> 组件中执行此操作。

Indeed. PrimeFaces (and standard JSF) does not re-evaluate the EL in on* attributes on a per-request basis. It only happens on a per-view basis. RichFaces however does that in <a4j:xxx> components.

您需要以不同方式解决问题。我建议使用< p：dialog> 的 visible 属性。

You need to solve the problem differently. I suggest to use the visible attribute of the <p:dialog> instead.

<h:form>
    ...
    <p:commandButton value="Delete all friends?" update=":deleteDialogs" />
</h:form>
...
<h:panelGroup id="deleteDialogs">
    <p:dialog id="deleteFriendsConfirmDialog" visible="#{facesContext.postback and not empty userBean.user.friendList}">
        ...
    </p:dialog>
    <p:dialog id="friendsAlreadyDeletedErrorDialog" visible="#{facesContext.postback and empty userBean.user.friendList}">
        ...
    </p:dialog>
</h:panelGroup>

另一种方法是使用PrimeFaces' RequestContext 在bean的action方法中，它允许你以编程方式在bean的action方法中执行JavaScript代码（虽然这与控制器有点过多地与视图，IMO结合）。

An alternative is to use PrimeFaces' RequestContext in the bean's action method which allows you to execute JavaScript code programmatically in bean's action method (although this tight-couples the controller a bit too much with the view, IMO).

<p:commandButton value="Delete all friends?" action="#{userBean.deleteAllFriends}" />

with

RequestContext context = RequestContext.getCurrentInstance();

if (!user.getFriendList().isEmpty()) {
    context.execute("deleteFriendsConfirmDialog.show()");
} else {
    context.execute("friendsAlreadyDeletedErrorDialog.show()");
}

---

不相关对于具体问题，您的原始 onclick 虽然在您的特定情况下不起作用，但显示了一些不良做法。 javascript：伪协议是多余的。这已经是默认值了。去掉它。对 =='true'的测试也是多余的。去掉它。只需让EL直接打印 true 或 false 。以下是正确的语法（再次，这不能解决您的问题，只是为了您的信息）

---

Unrelated to the concrete problem, your original onclick, while it does not work out in your particular case, shows some poor practices. The javascript: pseudoprotocol is superfluous. It's the default already. Remove it. Also the test against == 'true' is superfluous. Remove it. Just let the EL print true or false directly. The following is the proper syntax (again, this does not solve your problem, just for your information)

<p:commandButton
    onclick="if (#{not empty userBean.user.friendList}) deleteFriendsConfirmDialog.show(); else friendsAlreadyDeletedErrorDialog.show();"
    value="Delete all friends?" />

如果您使用的是RichFaces的< a4j：commandButton> ; 。

It would have worked if you were using RichFaces' <a4j:commandButton>.

<a4j:commandButton
    oncomplete="if (#{not empty userBean.user.friendList}) deleteFriendsConfirmDialog.show(); else friendsAlreadyDeletedErrorDialog.show();"
    value="Delete all friends?" />

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