How to know whether JSF bean setter is invoked from AJAX event or as part of form POST processing

Question

I have a form that contains a Part Number inputText field and some other fields that represent the attributes of a part. If the user enters an existing part number, I want to populate the other fields with the part's existing attributes. The operator then has the option to change Part Number to something else (essentially creating a new part using the existing part as a template) and/or modify its attributes. I have an AJAX event defined to update the model when Part Number changes, so I can retrieve the attributes from the database:

<f:ajax event="valueChange" execute="@this" render="partlength" />

My question is this: How does the Part Number setter (e.g. setPartNumber() ) know whether it is being invoked as part of an AJAX event, in which case I want to fetch the attributes, or as part of the Update Model Values phase of the form being posted, in which case I don't? Or is there a better way to accomplish what I'm trying to do?

Answer 1

You can determine by PartialViewContext#isAjaxRequest() whether the current request is an ajax request or not. You can obtain the PartialViewContext by FacesContext#getPartialViewContext().

if (FacesContext.getCurrentInstance().getPartialViewContext().isAjaxRequest()) {
    // The current request is an ajax request.
}

An alternative is to just do the job in the listener method of <f:ajax> instead of in the getter/setter (doing business job in getters/setters is a poor practice anyway):

<f:ajax listener="#{bean.listener}" render="partlength" />

(note that I omitted the event and execute attributes as you've used the default values already)