RichFaces Interview Questions and Answers

Attribute "eventsQueue" defines the name of the queue that will be used to order upcoming Ajax requests. By default, RichFaces does not queue Ajax requests. If events are produced simultaneously, they will come to the server simultaneously. JSF implementations (especially, the very first ones) does not guaranty that the request that comes first will be served or passed into the JSF lifecycle first. The order how the server-side data will be modified in case of simultaneous request might be unpredictable. Usage of eventsQueue attribute allows to avoid possible mess.

The next request posted in the same queue will wait until the previos one is not processed and Ajax Response is returned back if the  "eventsQueue"  attribute is defined.

There are different ways to send Ajax requests from your JSF page. For example you can use <a4j:commandButton>  ,  <a4j:commandLink> ,  <a4j:poll>   or  <a4j:support>  tags or any other.

Given an example below:

A4J.AJAX.onError = function(req, status, message){

    window.alert("Custom onError handler "+message);

}

A4J.AJAX.onExpired = function(loc, expiredMsg){

if(window.confirm("Custom onExpired handler "+expiredMsg+" for a location: "+loc)){

      return loc;

    } else {

     return false;

    }