java JSTL foreach隐藏输入提交空值

Question

我正在做一个类似于在线商店的小型JEE5应用程序，我需要展示商店产品，代码中可以更清楚地看到：

<c:forEach var="product" items="${productsBean.products}">
  <div class ="product">
   <table>
    <td>
     <c:out value="${product.id}"/>
    </td>
    <td>
     <c:out value="${product.name}"/>
    </td>
    <td>
     <c:out value="${product.price}"/>
    </td>
    <td>
     <c:out value="${product.description}"/> 
    </td>
    <td>
    <form method="post" action="/servlets-war/AddToCart">
     <input type="hidden" name="id" value="${product.id}"></input>
     <input type="submit" value="add to cart"/>    
    </form>
   </td>
  </table>
 </div>
</c:forEach>

问题是表单中的隐藏输入值在提交表单时返回null而不是${product.id}

关联的servlet代码如下所示：

protected void processRequest(HttpServletRequest request,
        HttpServletResponse response)
        throws ServletException, IOException {

    ShoppingCart shoppingCart = (ShoppingCart)request.getSession()
            .getAttribute("shoppingCart");

    if(shoppingCart == null){
    shoppingCart = new ShoppingCart();
    }

    ProductsBean store =(ProductsBean) request
            .getSession().getAttribute("productsBean");

    int id = Integer.parseInt((String)request.getAttribute("id"));

    Product temp = store.getProduct(id);

    shoppingCart.getProducts().add(temp);

    request.getSession().setAttribute("shoppingCart", shoppingCart);

    this.getServletContext().getRequestDispatcher("/shop.jsp")
            .forward(request, response);
}

Answer 1

您正在将id作为请求属性检索

int id = Integer.parseInt((String)request.getAttribute("id"));

表单输入作为请求参数发送到servlet。适当更改代码：

int id = Integer.parseInt((String)request.getParameter("id"));