CommerceCommandServlet has an actionMap property that matches actions to the servlets that process those actions. When a request includes a dcs_action parameter, CommerceCommandServlet checks the value of the dcs_action, locates the action’s corresponding servlet using actionMap, and calls that servlet. For example, if a request attempts to add an item to a user’s cart by URL, the dcs_action is addItemToCart and the AddItemToCartServlet is called.

For more information, see on this servlet, see the ATG Commerce Programming Guide.