Now, I have specified type as button, so I expected that it will not go to action on click on the button.
But what happens is
when I click on button, it asks if I want to close the window,
Now, even I click NO, it still goes to action specified in form.
Solution : This is a BUG in struts2.
the HTML tag that is generated is something like:
<button type="submit" id="test_0" value="Submit" class="button positive save">Submit</button>
Please note that we have given type=button in s:submit tag, and the HTML generated still contains type=submit.
Can get some information from http://www.ericmmartin.com/struts-2-bug-submit-button-tag-rendering/