Question

我目前正在制作一个网站，您可以在其中制作松饼。松饼由Topping和Bottom组成。它通过2个表格，底部和顶部的名称和价格。这是我用来编写每个项目的功能，无论是打顶还是打底：

public String writeTopping(){
        String output = ""; 
        String topping;

        double price;
        try {

            Class.forName("com.mysql.jdbc.Driver");   
            Connection myConn = DriverManager.getConnection("jdbc:mysql://", "asdasd", "asdasdas");
            java.sql.Statement mySt = myConn.createStatement();
            String rs = "SELECT * FROM topping";
            ResultSet myRS = mySt.executeQuery(rs);
            while (myRS.next()) {
                topping = myRS.getString("topping");
                price = myRS.getDouble("price");
                topping tempTop = new topping(topping, price);
                 toppingCake.add(tempTop);
                 output += "<form method ='POST' action='Topping'><div class='panel panel-primary'><div class='panel-heading'>" + topping + "</div><div class='panel-body'><img src='http://placehold.it/150x80?text=IMAGE' class='img-responsive' style='width:100%' alt='Image'></div><div class='panel-footer'>Price: "+ price +"</div><button type='submit'>Add To Basket</button><input type='hidden' name='topping' value='"+topping+"'></div>";

            }

            myConn.close();
        } catch (SQLException | HeadlessException ex) {
            JOptionPane.showMessageDialog(null, ex);
        } catch (ClassNotFoundException ex) {
            Logger.getLogger(DBHandler.class.getName()).log(Level.SEVERE, null, ex);
        }
        items.add(output);
        return output;



    }

单击提交时，在任一项上，servlet会设置您选择的顶部属性：

String toppingPage = request.getParameter("topping");

        switch (toppingPage) {
            case "Chocolate":
                request.setAttribute("topping", toppingPage);
                response.sendRedirect("secondPage.jsp");
                break;
            case "Blueberry":
                request.setAttribute("topping", toppingPage);
                response.sendRedirect("secondPage.jsp");
                break;
            case "Rasberry":
                request.setAttribute("topping", toppingPage);
                response.sendRedirect("secondPage.jsp");
                break;
            case "Crispy":
                request.setAttribute("topping", toppingPage);
                response.sendRedirect("secondPage.jsp");
                break;
            case "Strawberry":
                request.setAttribute("topping", toppingPage);
                response.sendRedirect("secondPage.jsp");
                break;
            case "Raisin":
                request.setAttribute("topping", toppingPage);
                response.sendRedirect("secondPage.jsp");
                break;
            case "Orange":
                request.setAttribute("topping", toppingPage);
                response.sendRedirect("secondPage.jsp");
                break;
            case "Lemon":
                request.setAttribute("topping", toppingPage);
                response.sendRedirect("secondPage.jsp");
                break;
            case "Blue Cheese":
                request.setAttribute("topping", toppingPage);
                response.sendRedirect("secondPage.jsp");
                break;
        }

在最后一页，我会用

显示结果

<% out.print(session.getAttribute("topping")); %>

我今天早些时候有这个工作，但是，我改变了一些东西，现在它因某种原因不断返回null。

会话属性不再有效？

0 个答案: