How can I prevent the shopping cart item from incrementing when the user refresh the page?

Question

I made a shopping cart using servlet and jsp but i'm facing a problem which increments the quantity of cart item whenever I refresh the cart page. Actually what i'm doing is passing the particular product ID in the url whenever user click the add to cart button on some product just like addtocart.jsp?id=3 and then in according to the id I extract the product from the database and add it in the cart but when I refresh this URL addtocart?id=3 the whole procedure in this page run again which increments the product quantity everytime of a refresh. How can I solve this problem. Any suggestions?

product.jsp

<%
 String id = request.getParameter("id");
 Connection con = ConnectionManager.getConnection();
 PreparedStatement ps = con.prepareStatement("Select * from products inner join images using(product_name) "
         + "where product_id=?");
 ps.setString(1,id);
 ResultSet rs= ps.executeQuery();
 rs.next();

 String name = rs.getString("product_name");
 String image = rs.getString("image_name");
 String company = rs.getString("company_name");
 String category =  rs.getString("category_name");
 String sub = rs.getString("sub_category_name");
 double price = rs.getDouble("price");
 String summary = rs.getString("summary");
 int hits = rs.getInt("hits");

 //out.println(price);
%>
   <div class="container_16" style="background: #FFF;">
       <div class="grid_16 productHeading">
           <h2 class="heading"><%=name %>- By <%= company %> <%=category%> </h2>
       </div>

       <div class="grid_10">

             <h5>Category: <a href="#" onclick="return false"><%= category %> </a> >
              <a href="#" onclick="return false">  <%= sub %> </a><br/><br/>
              Priced At <span class="Bigred">RS. <%=price %></span> 
             </h5>

             <h2>Summary Of this Item</h2>


                       <div class="grid_5" id="addtocart">
                           <a href="addToCart.jsp?id=<%=id%>">
                              Add To Cart
                           </a>
                           <% if(session.getAttribute("admin")!=null)
                              {
                           %>   
                              <a href="addToCart.jsp?id=<%=id%>">
                              Edit  
                           </a>
                          <%              
                            }
                           %>   
                       </div>

               <br/>

             <h6 class="grey">Summary of <%= name%></h6>
                    <p class="info">
                        <%= summary%>
                    </p>       

       </div>  

       <div class="grid_4" id="pimage">
           <img src="<%= image%>">
       </div>    

  </div>

Search the cart to see if the submitted ID already exists, then do nothing? — Gimby, Jul 15 '16 at 09:04

score 2 · Answer 1 · answered Jul 15 '16 at 09:06

2

Use Post/Redirect/Get Pattern:

Submit form with POST method instead of GET
Redirect back to cart page after processing post request.

https://en.wikipedia.org/wiki/Post/Redirect/Get

answered Jul 15 '16 at 09:06

Konstantin Pavlov

956
1
10
24

score 0 · Answer 2 · edited May 23 '17 at 12:14

0

Here are some possibilities to prevent this from happening.

Change the form method to POST so that the browser asks the user if they want to resubmit the form if they ever refresh
Redirect the form after it is accepted

Have a look at the answers to this question How to avoid resubmit in jsp when refresh?

After looking at your edited code, I would suggest adding code to remove the session variable after it is processed OR just use a hidden form and pass the parameters using the input tags

edited May 23 '17 at 12:14

Community

1
1

answered Jul 15 '16 at 08:37

Seda

243
1
9

but I'm not using a form it is just a simple link to the addtocart.jsp – palak sharma Jul 15 '16 at 08:42
can I do it without using the form and hidden parameter? – palak sharma Jul 15 '16 at 08:51
Let me get this straight, every time a customer adds something to the cart, they are redirected to a new page? – Seda Jul 15 '16 at 08:56
yes they are redirected to the addtocart.jsp with an id – palak sharma Jul 15 '16 at 08:58
That doesn't seem right. Anyway, look at my edited answer – Seda Jul 15 '16 at 09:00

score 0 · Answer 3 · edited May 23 '17 at 12:08

0

look at your code

  <a href="addToCart.jsp?id=<%=id%>">

use

        var url="addtocart.jsp";
        url +="?id=" +value;

and pass url as GET method

or

<a href="addToCart.jsp?id="<%=id%>>

not resolve then follow

How to pass the values from one jsp page to another jsp without submit button?

edited May 23 '17 at 12:08

Community

1
1

answered Jul 15 '16 at 09:06

Dheeraj Upadhyay

336
2
12

How can I prevent the shopping cart item from incrementing when the user refresh the page?

3 Answers3