Bridging to Open Ajax

Please note that if you don't have an interest in Open Ajax, this post may not be especially illuminating - I've talked about the addOnEvent function before, even recently.

To write an Open Ajax application, you need to subscribe to events, much like in JSF 2, by registering functions which act as listeners. For instance, suppose we had a field in our page that looked like this:

 <textarea id="statusArea" cols="40" rows="10" readonly="readonly" />

   1 var statusUpdate = function statusUpdate(name, data) {
   2     var statusArea = document.getElementById("statusArea");
   3     var text = statusArea.value;
   4     text = text + "Name: "+data.source.id;
   5     if (name === "jsf.event") {
   6         text = text +" Event: "+data.status+"\n";
   7     } else if (name === "jsf.error") {  
   8         text = text + " Error: "+data.status+"\n";
   9     }
  10     statusArea.value = text;
  11 };
  12 
  13 OpenAjax.hub.subscribe("jsf.event",statusUpdate);
  14 OpenAjax.hub.subscribe("jsf.error",statusUpdate);

So, where do those messages come from? Unlike JSF, the OpenAjax hub has a publish function, in addition to a subscribe function. By associating that publish function with a call to jsf.ajax.addOnEvent and jsf.ajax.addOnError, we can bridge between the two event systems - like this:

   1 var openajaxbridge = {};
   2 
   3 openajaxbridge.eventUpdate = function eventUpdate(data) {
   4     OpenAjax.hub.publish("jsf.event", data);
   5 };
   6 
   7 openajaxbridge.errorUpdate = function errorUpdate(data) {
   8     OpenAjax.hub.publish("jsf.error",data);
   9 };
  10 
  11 jsf.ajax.addOnEvent(openajaxbridge.eventUpdate);
  12 jsf.ajax.addOnError(openajaxbridge.errorUpdate);