mysql - 将servlet的变量结果显示到jsp arraylist

Question

我正在尝试通过servlet将我的数据从mysql显示到jsp中我面临的问题是我不确定数据是否正在传递，我收到 NullPointerException 错误。它甚至不显示从 mysql 获取的任何数据

我想做的是将我的 mysql id、名称、价格中的所有数据以格式表显示到 jsp 中

结果.jsp

<%                           
        ArrayList<ProductBean> list=(ArrayList<ProductBean>)request.getAttribute("list");
        for (int i = 0; i < list.size(); i++) {
                list.get(i).getItemID();
                list.get(i).getName();
                list.get(i).getPrice();
            }
        %>

产品.java

  connection = DriverManager.getConnection(connectionUrl + dbName, userId, password);
            statement = connection.createStatement();
            String sql = "SELECT id,name,price FROM item";

            ArrayList < ProductBean > list = new ArrayList < ProductBean > ();

            resultSet = statement.executeQuery(sql);
            while (resultSet.next()) {
                String itemID = resultSet.getString("id"); //fetch the values present in database
                String name = resultSet.getString("name");
                String price = resultSet.getString("price");
                list.add(new ProductBean(itemID, name, price));

            }
            request.setAttribute("list", list); 
            request.getRequestDispatcher("/result.jsp").forward(request, response);

ProductBean.java

public class ProductBean {

    private String itemID;
    private String name;
    private String price;

    public String getItemID() {
        return itemID;
    }
    public void setItemID(String itemID) {
        this.itemID = itemID;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getPrice() {
        return price;
    }
    public void setPrice(String price) {
        this.price = price; 
    }

    public ProductBean(){
    }

    public ProductBean(String itemID, String name, String price){
        this.itemID = itemID;
        this.name = name;
        this.price = price;
    }
}

Answer 1

如果没有获得 NULL 指针异常，请使用 out.println() 显示

<%                           
        ArrayList<ProductBean> list=(ArrayList<ProductBean>)request.getAttribute("list");
        for (int i = 0; i < list.size(); i++) {
                 out.println(list.get(i).getItemID());
                 out.println(list.get(i).getName());
                 out.println(list.get(i).getPrice());
            }
        %>

使用也可以使用JSTL

<c:forEach var="i" items=${list}>
  <c:out value="${i.itemID}"/> 
  <c:out value="${i.name}"/> 
  <c:out value="${i.price}"/> 

</c:forEach>