用于 valueChangeListener 的 Ajax

Question

我正在使用 p:ajax监听器处理值更改事件(因为 valueChangeListener 在表单提交时启动):

<p:ajax event="change" listener="#{bean.onNameChanged}"/>

处理方法:

public void onNameChanged(final AjaxBehaviorEvent event)

问题是，我在 AjaxBehaviorEvent 中找不到也不是它的类层次结构是阅读 的地方旧值 的输入。我也无法在谷歌中找到提示，如何获得旧值...

如何访问 p:ajax onChange 中的旧值事件？

Answer 1

The problem is, I can't find in AjaxBehaviorEvent nor its class hierarchy the place to read the old value of the input. Neither could I find hint in google, how to get the old value...

使用 valueChangeListener .

Unfortunatelly, valueChangeListener is invoked before p:ajax, so I don't have actual data from forms in that method, so in theory I could use valueChangeListener to remember the old value and then wait for p:ajax to process...

将值更改事件排队到调用应用程序阶段。

public void valueChangeListenerMethod(ValueChangeEvent event) {
    if (event.getPhaseId() != PhaseId.INVOKE_APPLICATION) {
        event.setPhaseId(PhaseId.INVOKE_APPLICATION);
        event.queue();
        return;
    }

    // Do your original job here. 
    // It will only be invoked when current phase ID is INVOKE_APPLICATION.
}