Struts 2 AJAX tag questions

[Haitao Lok]

Hi,

I am learning how to use AJAX-enabled tags in Struts 2. Here is a code snippet:

1: <div style="text-align: right;">
2: <s:a theme="ajax" notifyTopics="/refresh">Refresh</s:a>
3: </div>
4: <s iv id="persons" theme="ajax" href="%{descrsUrl}"
5: loadingText="Loading..." indicator="indicator1"
6: listenTopics="/refresh"/>

Here are my questions:
1. I didn't see the 'refresh' topic declared anywhere in the file. Is it something that the <s:a> tag understands what to do with? And what exactly does line 2 mean?
2. What do lines 4 through 6 do here? I think I understand the id, theme, href, loadText and indicator attributes here.

Thanks in advance.

Haitao

[Guang Ji]

I have the same question.