从 preRender 导航后无法保留人脸消息 [英] Can't keep faces message after navigation from preRender

问题描述

在我的页面预渲染代码中，我添加了faces消息，然后导航到另一个页面，如下所示:

in my preRender code for a page i add faces message then make navigation to another page as follows:

if(error){
addMessageToComponent(null,"AN ERROR HAS OCCURRED");
FacesContext.getCurrentInstance().getExternalContext().getFlash()
                .setKeepMessages(true);
navigateActionListener("myoutcome");
}

以及用于添加消息和导航的 util 方法是:

and the util methods for adding message and navigation are:

public static String getClientId(String componentId)
    {
        FacesContext context = FacesContext.getCurrentInstance();
        UIViewRoot root = context.getViewRoot();

        UIComponent c = findComponent(root, componentId);
        return c.getClientId(context);
    }

    public static UIComponent findComponent(UIComponent c, String id)
    {
        if (id.equals(c.getId())) { return c; }
        Iterator<UIComponent> kids = c.getFacetsAndChildren();
        while (kids.hasNext())
        {
            UIComponent found = findComponent(kids.next(), id);
            if (found != null) { return found; }
        }
        return null;
    }

    /**
     * @param componentId
     *            : the id for the jsf/primefaces component without formId:
     *            prefix. <br>
     *            if you use null then the message will be added to the
     *            h:messages component.
     **/
    public static void addMessageToComponent(String componentId, String message)
    {

        if (componentId != null)
            componentId = GeneralUtils.getClientId(componentId);
        FacesContext.getCurrentInstance().addMessage(componentId,
                new FacesMessage(message));
    }

public static void navigateActionListener(String outcome)
    {
        FacesContext context = FacesContext.getCurrentInstance();
        NavigationHandler navigator = context.getApplication()
                .getNavigationHandler();
        navigator.handleNavigation(context, null, outcome);
    }

但是消息不会被保存，所以它不会在重定向后出现.

but messages are not saved and so it doesn't appear after redirect.

请告知如何解决这个问题.

please advise how to fix that.

推荐答案

preRenderView 事件在 RENDER_RESPONSE 阶段的最开始运行.指示 Flash 作用域保留消息为时已晚.您最迟可以在 INVOKE_APPLICATION 阶段执行此操作.

The preRenderView event runs in the very beginning of the RENDER_RESPONSE phase. It's too late to instruct the Flash scope to keep the messages. You can do this at the latest during the INVOKE_APPLICATION phase.

由于没有标准的 JSF 组件系统事件，您需要自制一个:

Since there's no standard JSF component system event for this, you'd need to homebrew one:

@NamedEvent(shortName="postInvokeAction")
public class PostInvokeActionEvent extends ComponentSystemEvent {

    public PostInvokeActionEvent(UIComponent component) {
        super(component);
    }

}

要发布此内容，您需要一个 PhaseListener:

To publish this, you need a PhaseListener:

public class PostInvokeActionListener implements PhaseListener {

    @Override
    public PhaseId getPhaseId() {
        return PhaseId.INVOKE_APPLICATION;
    }

    @Override
    public void beforePhase(PhaseEvent event) {
        // NOOP.
    }

    @Override
    public void afterPhase(PhaseEvent event) {
        FacesContext context = FacesContext.getCurrentInstance();
        context.getApplication().publishEvent(context, PostInvokeActionEvent.class, context.getViewRoot());
    }

}

在faces-config.xml中如下注册后:

<lifecycle>
    <phase-listener>com.example.PostInvokeActionListener</phase-listener>
</lifecycle>

您可以按如下方式使用新事件:

You'll be able to use the new event as follows:

<f:event type="postInvokeAction" listener="#{bean.init}" />

你只需要确保你至少有一个，否则JSF根本不会进入调用阶段.

You only need to make sure that you've at least a <f:viewParam>, otherwise JSF won't enter the invoked phase at all.

JSF 实用程序库 OmniFaces 已经支持此事件，并且开箱即用的 preInvokeAction 事件.另请参阅展示页面，该页面还演示了如何设置面部消息以进行重定向.

The JSF utility library OmniFaces already supports this event and the preInvokeAction event out the box. See also the showcase page which also demonstrates setting a facesmessage for redirect.

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