[jQuery] jquery_ajax + servlet problem

[jQuery] jquery_ajax + servlet problem


It takes me almost half a day , but I haven't solve it ,I don't know
why .
I would be much appreciate for your help...
$(document).ready(function(){
alert("can show");
$("#button").click(function(){
alert("when click button , can show ");
$.post("AddComment",null,function(data){ //
AddComment is a servlet name
alert("here can't show");
},"json");
});
});
servlet ,root ,"servlets/AddComment",
public void doPost(HttpServletRequest request, HttpServletResponse
response)
throws ServletException, IOException {
System.out.println("here can't show,that is ,the method
$.post does not work");
}
servlet config in web.xml:
<servlet>
<servlet-name>AddComment</servlet-name>
<servlet-class>servlets.AddComment</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>AddComment</servlet-name>
<url-pattern>/servlets/AddComment</url-pattern>
</servlet-mapping>