Question

This is my code

    <%
   if(request.getParameter("cart") != null)
    {
     ......
     }
    <%

   <form method="post"><input  class="auto-style2"  height="44" name="cart" 
    src="divers/panier.jpg" type="image" width="71" />

So when I press the button name=”cart” I can get request.getParameter(“cart”).

How to know its a post back when I click on the img ?

Answer 1

How to know its a post back when I click on the img ?

Check the request method.

if ("post".equalsIgnoreCase(request.getMethod())) {
    // It's a POST request.
}

Or, better, let the form submit to a servlet and do the job in doPost() method.

---

Unrelated to the concrete problem, you’re in essence abusing the <input type="image"> here to have just a button with a background image. It will not sent a request parameter cart, but instead send the mouse cursor position on the image as cart.x and cart.y. You need to check those parameters instead.

if (request.getParameter("cart.x") != null) {
    // Image button is clicked.
}

See also HTML Input (type=image) not working on Firefox 4.