On the product page, we used a simple form to display an Add to comparison list button. We used the ProductListHandler.addProduct method to add the product the user is viewing to a list of products to compare.

The Product page includes a section for adding items to and viewing the comparison list.

A View comparison list link is displayed on the page if there are products in the comparison list. Once a user adds a product to the list, the button is changed to display Remove from list and to use the ProductListHandler.removeProduct method so that the product can be removed from the list.

When a product is on the comparison list, the button changes to display “Remove from list.”

Below is the code we used to implement the Product Comparisons section on the product page.

<dsp:form action="product.jsp" method="post">
  <tr>
    <td bgcolor="#E5E5E5">
    <input name="id" type="hidden" value="<dsp:valueof
      param="element.repositoryId"/>">
    <dsp:input bean="CartModifierFormHandler.SessionExpirationURL" type="hidden"
      value="../common/session_expired.jsp"/>
    <dsp:input bean="CartModifierFormHandler.productId"
      paramvalue="product.repositoryId" type="hidden"/>

    <dsp:droplet name="ProductListContains">
      <dsp:param bean="ProductList" name="productList"/>
      <dsp:param name="productID" param="element.repositoryId"/>
      <dsp:oparam name="true">
        <dsp:input bean="ProductListHandler.productID" paramvalue="productID"
          type="hidden"/>
        <dsp:input bean="ProductListHandler.removeProduct" type="submit"
          value="Remove from list"/>
      </dsp:oparam>
      <dsp:oparam name="false">
        <dsp:input bean="ProductListHandler.productID" paramvalue="productID"
          type="hidden"/>
        <dsp:input bean="ProductListHandler.addProduct" type="submit" value="Add
          to comparison list"/>
       </dsp:oparam>
     </dsp:droplet>
  </td>
</tr>
<!--check to see if there are items in comparison list-->
<dsp:droplet name="IsEmpty">
  <dsp:param bean="ProductList.items" name="value"/>
  <dsp:oparam name="false">
<tr>
  <td><span class=smallb><dsp:a href="compare.jsp">View comparison
    list</dsp:a></td>
</tr>
  </dsp:oparam>
  </dsp:droplet>
  </dsp:form>