如果从表单触发Ajax并更新另一个表单，Facelets是否会重建整个页面? [英] Does Facelets rebuild the whole page if Ajax is trigger from a form and updates another?

问题描述

设置: 我有2种表格A和乙 我有一个A型的CommandLink:

<h:commandLink actionListener="#{homeView.selectDiv('homeUpdates')}">#{msg.homeUpdates}
   <f:ajax render=":B" execute="@this" />
</h:commandLink>

...将更新表格B.

问题是，当我单击ajax链接时，它也会重新生成A形，并从我拥有的ui:repeat中获取异常.这是正确的行为吗?它也应该重建表格A吗?

我正在使用JSF 2.2，并且表单A包含ui:fragment => ui:include => ui:repeat

=====添加了SSCCE ======= 按下更新B后，以下代码将无法运行！两次.它给出了重复ID的例外. ui:repeat的值不相关

<h:head>
</h:head>

<h:body>
    <h:form id="A">
        <ul class="tableView notification">
            <ui:repeat var="notification" value="#{dashboardBean.notifications}">
                <li>
                    xx
                </li>
            </ui:repeat>
        </ul>

        <h:commandLink value="Update B!" listener="#{dashboardBean.toggleRendered}">
            <f:ajax execute="@this" render=":B" />
        </h:commandLink>

    </h:form>

    <h:form id="B">
    </h:form>
</h:body>

解决方案

在初始请求时，将创建视图，回发后将恢复该视图.为了清楚起见，请列举 JSF 2.2规范的要点(强调我的观点):

P. 2.2.1 :

如果请求不是回发...在ViewHandler上调用 createView().如果请求是回发，则...调用ViewHandler. restoreView()，为当前请求传递FacesContext实例和视图标识符，并为还原后的视图返回UIViewRoot.

P. 2.5.8 :

可以对JSF视图中的

选择的组件进行优先处理(称为部分处理)，并且可以将选择的组件呈现给客户端(称为部分渲染).

P. 13.4 :

可以将JavaServer Faces生命周期视为执行阶段和呈现阶段.部分遍历是一种可用于访问"视图中的一个或多个组件的技术，有可能使它们通过请求处理生命周期的执行"和/或呈现"阶段.

使用AJAX时，PartialViewContext类将包含遍历还原的视图所需的所有信息.

---

因此，要回到您的问题，在<f:ajax render=":B" execute="@this" />设置下，将仅呈现具有id="B"的表单，这表示<h:form id="B">，没有表单嵌套等.

关于您的无效"评论，带有纯视图范围的托管Bean的简单测试用例为我带来了预期的结果:

<h:form id="A" >
    <h:outputText value="#{twoFormsBean.a}"/>
    <h:commandLink actionListener="#{twoFormsBean.actionA}">
        Update B!
        <f:ajax execute="@this" render=":B"/>
    </h:commandLink>
</h:form>
<h:form id="B" >
    <h:outputText value="#{twoFormsBean.b}"/>
    <h:commandLink>
        Update Both!
        <f:ajax execute="@this" render=":A :B"/>
    </h:commandLink>
</h:form>

使用

@ManagedBean
@ViewScoped
public class TwoFormsBean implements Serializable {

    private String a = "A";//getter
    private String b = "B";//getter

    public void actionA(ActionEvent ae) {
        a = "newA";
        b = "newB";
    }

}

Setup: I have 2 forms A & B I have a commandLink in form A:

<h:commandLink actionListener="#{homeView.selectDiv('homeUpdates')}">#{msg.homeUpdates}
   <f:ajax render=":B" execute="@this" />
</h:commandLink>

...which updates form B.

The problem is that when I click the ajax link, it rebuilds form A as well and gets an exception from a ui:repeat I have. Is this correct behaviour? Should it rebuild form A as well?

I am using JSF 2.2 and form A contains a ui:fragment=>ui:include=>ui:repeat

=====Added SSCCE======= The following code does not run after pressing Update B! twice. It gives an exception of duplicate id. The value for ui:repeat is irrelevant

<h:head>
</h:head>

<h:body>
    <h:form id="A">
        <ul class="tableView notification">
            <ui:repeat var="notification" value="#{dashboardBean.notifications}">
                <li>
                    xx
                </li>
            </ui:repeat>
        </ul>

        <h:commandLink value="Update B!" listener="#{dashboardBean.toggleRendered}">
            <f:ajax execute="@this" render=":B" />
        </h:commandLink>

    </h:form>

    <h:form id="B">
    </h:form>
</h:body>

解决方案

Upon initial request the view is created, upon postbacks the view is restored. To recite some points of JSF 2.2 specification for clarity (emphasis mine):

P. 2.2.1:

If the request is not a postback ... call createView() on the ViewHandler. If the request is a postback, ... call ViewHandler.restoreView(), passing the FacesContext instance for the current request and the view identifier, and returning a UIViewRoot for the restored view.

P. 2.5.8:

Selected components in a JSF view can be priocessed (known as partial processing) and selected components can be rendered to the client (known as partial rendering).

P. 13.4:

The JavaServer Faces lifecycle, can be viewed as consisting of an execute phase and a render phase. Partial traversal is the technique that can be used to "visit" one or more components in the view, potentially to have them pass through the "execute" and/or "render" phases of the request processing lifecycle.

When you use AJAX, PartialViewContext class will contain all the information that's needed to traverse the restored view.

---

So, to get back to your question, under <f:ajax render=":B" execute="@this" /> setup, only the form with id="B" will be rerendered, which implies <h:form id="B">, no form nestings, etc.

Regarding your 'doesn't work' comment the simple test case with a plain view scoped managed bean gave me the expected results:

<h:form id="A" >
    <h:outputText value="#{twoFormsBean.a}"/>
    <h:commandLink actionListener="#{twoFormsBean.actionA}">
        Update B!
        <f:ajax execute="@this" render=":B"/>
    </h:commandLink>
</h:form>
<h:form id="B" >
    <h:outputText value="#{twoFormsBean.b}"/>
    <h:commandLink>
        Update Both!
        <f:ajax execute="@this" render=":A :B"/>
    </h:commandLink>
</h:form>

with

@ManagedBean
@ViewScoped
public class TwoFormsBean implements Serializable {

    private String a = "A";//getter
    private String b = "B";//getter

    public void actionA(ActionEvent ae) {
        a = "newA";
        b = "newB";
    }

}

这篇关于如果从表单触发Ajax并更新另一个表单，Facelets是否会重建整个页面?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！