why my bean method is not get called?

I use jboss with jsf1_1. I am new in JSF.

why my bean method is not get called?

my jsp:

<h:commandButton value="Modify" action="#{mybean.modify}" />

my method of bean:

public void modify(){

System.out.println("in modify method");

return "modify";

}

my faces-config.xml

<navigation-rule>

<from-view-id>/mypage.jsp</from-view-id>

<navigation-case>

<from-outcome>modify</from-outcome>

<to-view-id>/mypage.jsp</to-view-id>

</navigation-case>

</navigation-rule>

[626 byte] By [sh_sadraia] at [2007-11-26 23:53:11]